# AC Manifold Gauges



## BigJim (Sep 2, 2008)

I have been looking for a set of gauges and so far I am a little confused which set to buy. Back in the 60s when I was a mechanic I went to AC school for cars, I can't remember much from back then. I want to relearn how to do AC work but mostly on cars. I plan to take some tech school or online lessons. Any suggestion where I may start looking? 

I don't plan to do this work for a living as I am retired, just want to learn to piddle on my car/truck and for my kids and grandkids. Any suggestions which gauges would some of you suggest? There seems to be really cheap ones and some pretty high.


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## beenthere (Oct 11, 2008)

*Re: Manifold Gauges*

Don't do automotive myself. But the only thing you need different from home A/Cs, is the adapters to connect to the auto fittings.

How often you will work on them, is probably what should determine how good of a manifold you get.

PS: You might want to move this to the Automotive forum.


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## yuri (Nov 29, 2008)

*Re: Manifold Gauges*

I like CPS gauges and have been using them for 35 years. Not sure if you need anything special in them and I doubt it. You won't be checking subcooling and need temp probes I imagine.

Most car AC is done with a scale and you weigh in the freon charge. I would check with the Auto forum guys too.

http://www.cpsproducts.com/


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## BigJim (Sep 2, 2008)

*Re: Manifold Gauges*



beenthere said:


> Don't do automotive myself. But the only thing you need different from home A/Cs, is the adapters to connect to the auto fittings.
> 
> How often you will work on them, is probably what should determine how good of a manifold you get.
> 
> PS: You might want to move this to the Automotive forum.


BT I will probably use the gauges two or three times a year if that. I just didn't know if the cheaper gauges were any good or not.

I thought about posting this in automotive just after I posted it. Thanks.

Thanks Yuri, I appreciate that link.


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## ukrkoz (Dec 31, 2010)

http://www.homedepot.com/p/SPEEDWAY...vUVC5XB_kknvdudzUjXiJcxqwWf7IPkF3waAvB88P8HAQ


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## ukrkoz (Dec 31, 2010)

If you were to use them 3 times a year, you have serious issues with AC. I used mine twice in 4 yrs of ownership.


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## BigJim (Sep 2, 2008)

ukrkoz said:


> If you were to use them 3 times a year, you have serious issues with AC. I used mine twice in 4 yrs of ownership.


ukrkoz, not just our car and truck but our daughters, and grand kids. Thanks for the link, I appreciate it.

Now to learn all over again how to use them.


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## Brainbucket (Mar 30, 2015)

Just get a good set of gauges. The pressures are pretty much the same but the high side is a little higher than the r-12 pressures. It is critical that the right amount is installed. R-134-A is not as forgiving as r-12 if you add to much. A/C systems are most efficient at 1500 rpm. That is where I do my testing as at idle R-134-A pressures are not like r-12. Around 30lbs on low side and around 200-275lbs on high side depending on outside temps. Do not add oil as to much oil will make system not cool well. I starve the system of oil and never had any problems. I empty all the oil out of new compressors that have oil in them. And yes I get stares from other mechanics but I never had any problems and they do. And yes you have to pull a vacuum.:vs_cool:


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## BigJim (Sep 2, 2008)

Brainbucket said:


> Just get a good set of gauges. The pressures are pretty much the same but the high side is a little higher than the r-12 pressures. It is critical that the right amount is installed. R-134-A is not as forgiving as r-12 if you add to much. A/C systems are most efficient at 1500 rpm. That is where I do my testing as at idle R-134-A pressures are not like r-12. Around 30lbs on low side and around 200-275lbs on high side depending on outside temps. Do not add oil as to much oil will make system not cool well. I starve the system of oil and never had any problems. I empty all the oil out of new compressors that have oil in them. And yes I get stares from other mechanics but I never had any problems and they do. And yes you have to pull a vacuum.:vs_cool:


Thanks Bb, I appreciate your time and expertise, for me it is like starting totally from scratch, I can't remember much from years back at all. 

I really fouled up my 1990 Toyota 4X4 AC a couple years back. I was told I could use R-134-A in my R-12 system and it would work. Well he was right it did work, for a year, then it totally went south, the compressor won't even come on now. I love my little truck, I don't like the newer ones, that is the reason I want to keep my 1990. I do plan to replace everything AC, that way I know it is good to go for a few more years. Now on to learning. In Tennessee if you are a senior you can go to tech school free, I am thinking about doing just that. I am veeeery senior. lol


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## Brainbucket (Mar 30, 2015)

In r-12 systems, to convert them, you use 85% r-134a. Not the full amount that's required for your vehicle. It will work but not as efficiently as r-12. The r-12 oil is mineral oil for r-12 systems. Now they use pag (different car manufactures use different pag oil viscosity) oil for r-134a because r-134a wont grab the mineral oil and circulate it. The oil circulates with the freon. Now if the A/C compressor is low on the engine and the A/C hoses go up about a foot, you can put mineral oil in the compressor and use r-134a. I have done this and it worked on my own car. r-134a wont pick up the oil and circulate it. It stays in the compressor. But if not, the pressure will move it out of the comp and then boom. I would blow all the oil out of the system with air only. If you flush it, some stays in there and destroys the comp. A compressor for that vehicle would proly have mineral oil in it. Make sure. Some come without oil. Then I would install about 75% oil. Rotate the comp at least 10 times and charge it up. Or I would use a r-12 equivalent and mineral oil.:vs_cool:


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## BigJim (Sep 2, 2008)

Brainbucket said:


> In r-12 systems, to convert them, you use 85% r-134a. Not the full amount that's required for your vehicle. It will work but not as efficiently as r-12. The r-12 oil is mineral oil for r-12 systems. Now they use pag (different car manufactures use different pag oil viscosity) oil for r-134a because r-134a wont grab the mineral oil and circulate it. The oil circulates with the freon. Now if the A/C compressor is low on the engine and the A/C hoses go up about a foot, you can put mineral oil in the compressor and use r-134a. I have done this and it worked on my own car. r-134a wont pick up the oil and circulate it. It stays in the compressor. But if not, the pressure will move it out of the comp and then boom. I would blow all the oil out of the system with air only. If you flush it, some stays in there and destroys the comp. A compressor for that vehicle would proly have mineral oil in it. Make sure. Some come without oil. Then I would install about 75% oil. Rotate the comp at least 10 times and charge it up. Or I would use a r-12 equivalent and mineral oil.:vs_cool:


That is interesting, thanks a bunch.


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## ukrkoz (Dec 31, 2010)

Vacuum pump at HFT is less than a hundred bucks. You will need one.
As of how often used...

I am family mechanic for the family of 7 cars plus in laws... I even have car lift. I stay with what I said. Quality made sealed AC system runs for years and years and requires only can of freon/oil mix with hose and connector from any parts store. That normally covers 2 cars.
If you have to actually service all of those cars you mention at such frequency, there is issue.


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## BigJim (Sep 2, 2008)

ukrkoz said:


> Vacuum pump at HFT is less than a hundred bucks. You will need one.
> As of how often used...
> 
> I am family mechanic for the family of 7 cars plus in laws... I even have car lift. I stay with what I said. Quality made sealed AC system runs for years and years and requires only can of freon/oil mix with hose and connector from any parts store. That normally covers 2 cars.
> If you have to actually service all of those cars you mention at such frequency, there is issue.


ukrkoz, it isn't that often, it is just that it is that many who have problems that need fixing. I hadn't thought about HFT, Thanks for the suggestions.


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## BigJim (Sep 2, 2008)

I have been most of today trying to learn how the AC system works, all over again. Question, is the TXV valve the same as a metering device?


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## beenthere (Oct 11, 2008)

Yes, a TXV is a metering device.


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## BigJim (Sep 2, 2008)

beenthere said:


> Yes, a TXV is a metering device.


That is what I thought, I still haven't wrapped my head around why a TXV is necessary when a metering device would work. 

Another question, what determines the seer?

I have found a site where they give training for people wanting to get their certification, he explains things pretty good. I have gone through his basic video three times already and will probably view it a couple more times until I can drive it in my head which is latent and sensible temps, for some reason I can't seem to pound that into my head. Sensible you can't measure and latent you can, right?

One thing I did find very interesting is his example with water. You can put as much heat to water as you want to and the water will not get to more than 212 degrees, this is where sensible and latent come in.


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## BigJim (Sep 2, 2008)

Good grief, I just read about the new gas coming out in some new car AC. 1234yf, 10 pound bottle at O'Reilly's $999.99. Better buy a case or two of the R-134-A soon.


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## beenthere (Oct 11, 2008)

BigJim said:


> Good grief, I just read about the new gas coming out in some new car AC. 1234yf, 10 pound bottle at O'Reilly's $999.99. Better buy a case or two of the R-134-A soon.


You can get it for as low as $675.00 for 10 pounds. 

However, it may not be the gas that all new cars use starting in 2020. R134A may not be phased out as planned, now that we aren't part of the Paris convention.


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## BigJim (Sep 2, 2008)

BT That is still pretty high, compaired to R-22 or R-134_a.

BT, I have spent today and yesterday trying to soak up information on HVAC. This I can tell you this, there is no way I am going to try to learn all of that. Some people, think stair building is tough, I can tell you stair building is nowhere as hard as HVAC for me, except for maybe tangent rail fittings. There is no wonder why you folks charge so much.

Surly automotive HVAC can't be as hard as commercial and home HVAC, I guess I will find out if I can find some lessons online, good grief. I will say it is very interesting and I have learned quite a bit but going through the trouble of learning home, not to even mention commercial HVAC, is not for me, there is just way to much to it. 

Now on to automotive AC, I hope. LOL


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## Brainbucket (Mar 30, 2015)

House A/C is totally different than car A/C. The pressures are different. Yeah, you like Y-1234? They were trying to do CO2. 2600 psi. Can you imagine getting in an accident and that crap spraying everywhere? It would kill you.:surprise:


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## BigJim (Sep 2, 2008)

Brainbucket said:


> House A/C is totally different than car A/C. The pressures are different. Yeah, you like Y-1234? They were trying to do CO2. 2600 psi. Can you imagine getting in an accident and that crap spraying everywhere? It would kill you.:surprise:


Not me, I don't like anything that is taking people for a ride and the Y-1234 is doing just that. I would do without AC before I used that stuff.


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## beenthere (Oct 11, 2008)

BigJim said:


> BT That is still pretty high, compaired to R-22 or R-134_a.
> 
> BT, I have spent today and yesterday trying to soak up information on HVAC. This I can tell you this, there is no way I am going to try to learn all of that. Some people, think stair building is tough, I can tell you stair building is nowhere as hard as HVAC for me, except for maybe tangent rail fittings. There is no wonder why you folks charge so much.
> 
> ...


Automotive A/C is probably a good bit easier. But it can have its interesting dilemmas too.


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## BigJim (Sep 2, 2008)

I got another question, since I mixed R-134a with R-12 I know my AC system is shot, I should not have listened to a fellow about being able to mix them. I plan to replace the compressor, expansion valve, dryer, condenser and fittings, do I need to change out the evaporator and hoses also? This is on my 1990 Toyota 4X4 3.0 engine.


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## BayouRunner (Feb 5, 2016)

I would say no. Any particular reason you are changing condenser? Definitely the metering device, dryer and whatever component has failed. 


Sent from my iPhone using Tapatalk


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## BigJim (Sep 2, 2008)

I read where the condensers today have such small cooling holes that it is impossible to clean and blow them out now.

One reason I asked about the hoses is a fellow told me that the R-134a would just seep right through the R-12 hoses.

I actually don't know if the compressor is shot or not, I just figured it would be.


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## BayouRunner (Feb 5, 2016)

I haven't done much auto ac work. Just for the family, I'm always tinkering with something. I found with the foreign cars that it's best to weigh the charge. Some of those vehicles barely take any refrigerant and can easily be overcharged (learned the hard way, had to buy a new compressor). If there is no refrigerant in the system the low pressure switch will keep it from coming on. You can jump them out to test.


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## BigJim (Sep 2, 2008)

BayouRunner said:


> I haven't done much auto ac work. Just for the family, I'm always tinkering with something. I found with the foreign cars that it's best to weigh the charge. Some of those vehicles barely take any refrigerant and can easily be overcharged (learned the hard way, had to buy a new compressor). If there is no refrigerant in the system the low pressure switch will keep it from coming on. You can jump them out to test.


BR, I just saw last night on youtube how to jump the compressor, I will try that here soon. I am going to check to see if there is any freon in the system but I have got to get a set of guages first, These are the ones I plan to buy:

https://www.amazon.com/Manifold-Pro...id=1496769239&sr=1-17&keywords=ac+gauges+r134


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## Brainbucket (Mar 30, 2015)

2 different freon in the system? Empty the system. Blow out the entire system with air. Empty the compressor of r-12 oil by taking it off and dumping the oil out by rotating the clutch hub and having the holes upside down so oil can come out. Reinstall compressor and add 4oz of pag oil to your system. The parts house can tell you which oil to use. Turn clutch hub 10 revolutions. Pull a vacuum for an hour. Charge system with 85% of what r-12 is called for. Should work fine. DO NOT FLUSH WITH A/C FLUSH!!! And he is right that the r-12 hoses will leak but it's so minute that it doesn't matter. Enjoy the cool air.:vs_cool:


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## BigJim (Sep 2, 2008)

Brainbucket said:


> 2 different freon in the system? Empty the system. Blow out the entire system with air. Empty the compressor of r-12 oil by taking it off and dumping the oil out by rotating the clutch hub and having the holes upside down so oil can come out. Reinstall compressor and add 4oz of pag oil to your system. The parts house can tell you which oil to use. Turn clutch hub 10 revolutions. Pull a vacuum for an hour. Charge system with 85% of what r-12 is called for. Should work fine. DO NOT FLUSH WITH A/C FLUSH!!! And he is right that the r-12 hoses will leak but it's so minute that it doesn't matter. Enjoy the cool air.:vs_cool:


Thanks Bb, that is really good to know. I didn't know I could still get R-12. 

I have changed my mind on the gauges in the link in my last post, I saw on youtube were professional AC mechs are using the gauges from Harbor Freight, I usually stay away from Harbor Freight but I will probably get their gauges as others have said they work ok. I would love to have a set of Yellow Jackets but they are just a little out of my reach.


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## BigJim (Sep 2, 2008)

Wow, I just checked the price on R-12, man, they are really proud of that stuff. I probably will go ahead and convert to a R-134a system, at least if that needs to be replaced it won't be so bad.


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## Brainbucket (Mar 30, 2015)

The only thing that needs to be replaced is the drier and the fittings that will screw on your r-12 fittings so you can use the r-134 gauges. Sometimes you have to take out the old shrader valves, inside the r-12 fittings like a tire valve, so the new ones can work.:vs_cool:


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## BigJim (Sep 2, 2008)

Brainbucket said:


> The only thing that needs to be replaced is the drier and the fittings that will screw on your r-12 fittings so you can use the r-134 gauges. Sometimes you have to take out the old shrader valves, inside the r-12 fittings like a tire valve, so the new ones can work.:vs_cool:


Man you don't know how much I appreciate that, that will save me some serious dollars. 

Bb, you being in business for yourself you probably have Yellow Jacket gauges but they are just a little rich for my blood. What gauges would you recommend, I just plan to fool around with my stuff, our kids, and friends, so a very few times a year is about all I will do.


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## Brainbucket (Mar 30, 2015)

Harbor Freight should be ok. I have Robin Air but I use the hell out of them. Just make sure the needle is at zero on the gauge when there is no pressure so you get the right readings. There should be a screw at the bottom of the gauge face to set the needle. If that's not there, then get one that does. Remember, r-134 doesn't do as well as r-12 in a r-12 system but it does cool. I have converted many. They do have r-12 substitutes as freeze 12 and such. I would do that instead of r-134 but r-134 is still ok.:vs_cool:


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## BigJim (Sep 2, 2008)

Bb, you are a wealth of good information, I really do appreciate it. Now to see if I can get the compressor to kick in. Do you think the metering device will be clogged after mixing the two?


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## BigJim (Sep 2, 2008)

I got a question, I bought the Harbor Freight gauges because they had them on sale this weekend, today was the last day. These gauges are for R-134a and the instructions say to use on R-134a only. If I buy the adapters for R-12 that will fit on the R-134a gauges, will that work, or are these gauges only for R-134.


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## Brainbucket (Mar 30, 2015)

This is a retro-fit kit from NAPA Part: ATM 1700001 . Those are the fittings you need to install on your system so your r-134 gauges can connect. You are modifying the vehicles A/C system, not your gauges. If the compressor won't come on, usually it's the low pressure cycling switch that won't let it come on. Just jump the connection and charge the system. Then it should work correctly.:vs_cool:


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## BigJim (Sep 2, 2008)

Once again Bb, thanks a million. I have spent hours and hours reading and watching everything I can find about auto HVAC, I am starting to get a slight idea where I am not completely overwhelmed now. Sorta like when I was building years back. I would get a set of plans to build a large house with every roof pitch, dormer, hip and other roof design the architect could think up. At first I was overwhelmed, but building a house is like putting a puzzle together, one piece at a time. When looking at it like that, it was pretty simple. That is what I am doing trying to learn auto AC again, this time I am taking notes. LOL

At least I know now where to start if the clutch doesn't kick in. The reason I asked about using the R-134a gauges on an R-12 system, I read where it is not good to cross contaminate the compressor oil. Then I read where there wasn't enough oil left in the gauges to do much contaminating anyway.

I got to thinking that there are gauges that are Compatible with R22 R12 R134-A R502 R410A R502 so I am not going to worry about it. I already have my truck that has both R-12 and R-134a mixed so no worry there, I don't think, since I am starting from scratch on the truck.

Once again Bb, thank you, you have helped me more than you know and I appreciate it.


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## BigJim (Sep 2, 2008)

I just went out and hooked up the gauges, the engine is up to operating temps, outside temps are 85 F about 90 in the sun. The first picture is with the engine off, second picture is with engine running with AC on, fan at Number 3, no re-circ on. I would say the system is way over charged.

What next?


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## Brainbucket (Mar 30, 2015)

Yep. 30 psi at 1500 rpm but it looks like your compressor is damaged. if it was over charged, high side would be real high. get it down to 30 psi at 1500 rpms and show a pic of the gauges. but I believe the low side reed valves are bad. Test at max cool. high fan and recurt on.


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## BigJim (Sep 2, 2008)

Brainbucket said:


> Yep. 30 psi at 1500 rpm but it looks like your compressor is damaged. if it was over charged, high side would be real high. get it down to 30 psi at 1500 rpms and show a pic of the gauges. but I believe the low side reed valves are bad. Test at max cool. high fan and recurt on.


I was afraid the compressor was damaged also. I know I over charged it one time and the compressor made some strange sounds until I brought the pressure down some. I will hook the gauges back up and run it at 1500 rpm and see what it reads, I will try to get the low side to 30.


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## BigJim (Sep 2, 2008)

Bb, I checked outside temps, it is 92 right now in the shade. I ran it up to 1500 rpm and the first picture is when I first hooked it up and the car had run for a minute or so at 1500 rpm, AC wide open.

The second picture is after it ran for about 15 minutes at 1500 rpm.


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## Brainbucket (Mar 30, 2015)

BigJim said:


> Bb, I checked outside temps, it is 92 right now in the shade. I ran it up to 1500 rpm and the first picture is when I first hooked it up and the car had run for a minute or so at 1500 rpm, AC wide open.
> 
> The second picture is after it ran for about 15 minutes at 1500 rpm.


That looks great!:vs_karate: Now how cold does it get?


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## BigJim (Sep 2, 2008)

Whew, man I glad to hear that, it is too hot out there to change out a compressor. LOL

56 degrees at the vent. I may have to take the gauges back, the high pressure adapter is really hard to hook up and the knob is really stiff.

Thank you once again buddy, I really do appreciate your help.


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## Brainbucket (Mar 30, 2015)

Now your getting somewhere. Let some more out to get it to 30psi. let it run for a little while to stabilize the system. then let just a puff out and let it run at 1500 rpm. once it hits 30psi stop. It should be in the high 40's or very low 50's at the vent. High fan, max cool, recirt on, windows up. Good job.:vs_cool:


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## BigJim (Sep 2, 2008)

Brainbucket said:


> Now your getting somewhere. Let some more out to get it to 30psi. let it run for a little while to stabilize the system. then let just a puff out and let it run at 1500 rpm. once it hits 30psi stop. It should be in the high 40's or very low 50's at the vent. High fan, max cool, recirt on, windows up. Good job.:vs_cool:


I will sure do that Bb, You flat out know your stuff. I think the reason I got the reading I did, when I first hooked up the gauges, is I didn't bleed the air out of the new hoses like I was supposed to. I will let you know how it goes when I release some more pressure. I got to take the coupling back in the morning. Thanks ever so much again buddy, not many people would take their time to help like you have, I really do appreciate it.


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## Brainbucket (Mar 30, 2015)

Your more than welcome. r-134 takes a little time to stabilize. It doesn't go to regular pressure right off the bat. Let it run a little while before adjusting pressure.:vs_cool:


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## BigJim (Sep 2, 2008)

Brainbucket said:


> Your more than welcome. r-134 takes a little time to stabilize. It doesn't go to regular pressure right off the bat. Let it run a little while before adjusting pressure.:vs_cool:


Thanks buddy, I didn't know that. Now on to three more ACs, our daughter's 2002 VW, my 1990 Toyota 4X4 and our grandson's 2005 KIA. It is a whole lot different actually doing in real life than watching on videos. I have sent a lot of hours watching every kind of video on AC that I can find. You have helped me more than watching videos.

Headed to Harbor Freight to change out the coupling on the gauges.

Have a great day Bb.


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## BigJim (Sep 2, 2008)

Question, normal readings are 20-30 low side and 200-300 high side. Here is a chart I found, does this apply to auto AC and home AC or just one of them:

Microsoft Word don't post right so I took a picture of the chart:


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## BigJim (Sep 2, 2008)

Here are some notes I have come up with while watching some videos and what Bb has told me here. If any of this is not right please let me know. Also if you can think of anything to add I sure would appreciate.

1.	Connect gauges to system (engine off)
2.	(If LOW READING both sides)
3.	If both Low and High Side read Zero, system is empty and may have a leak. Normal should be about 120-125 with engine NOT running
4.	Inspect at all the system visually, to see if any oil leaking evidence is visible
5.	Crank engine and run until up to operating temps
6.	Once warmed up, set engine to 2000 RPM 
7.	Low Side and High Side reading below normal readings= low on Freon
8.	If Low Side reading is too low and High Side is too high= blockage in system (usually expansion valve)
9.	If Low Side reading is high and High Side reading is low and needle oscillating= Faulty reed valve in compressor (rebuild or replace compressor) 
10.	If both Low Side and High Side readings are too high= Over charged system
11.	If both Low and High side readings are the same (engine running)= the compressor is not working and needs replacing 
12.	When the compressor clutch kicks off, the pressure on the low side pressure will rise and the high side pressure will fall, this is normal.
13. When compressor clutch re-engages, the low side will fall and the high side will rise, this is normal and shows the clutch is working.
14. With engine running, and both low and high sides are reading about 125 PSI= the expansion valve or orifice tube is fully open usually, but the compressor or clutch could be bad, need to check it out.
15. Checking for leaks, put UV leak detector fluid in system(in low side, with engine running), run engine for about 30 minutes. Shut off engine and using a UV flash light or UV goggles look for colored leak fluid.


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## 47_47 (Sep 11, 2007)

It's been a long time but step 3, low and high side pressures should be the same and equal to ambient air temp (F) for a fully charged system.


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## BigJim (Sep 2, 2008)

47_47 said:


> It's been a long time but step 3, low and high side pressures should be the same and equal to ambient air temp (F) for a fully charged system.


47, Would this be an example? The outside temps at 95, both low and high side should read 95 with engine not running? I am a little thick, it takes me a little while to grasp some things.


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## 47_47 (Sep 11, 2007)

BigJim said:


> 47, Would this be an example? The outside temps at 95, both low and high side should read 95 with engine not running? I am a little thick, it takes me a little while to grasp some things.


Yes, all should be the same with the AC off and stabilized


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## Brainbucket (Mar 30, 2015)

BigJim said:


> Here are some notes I have come up with while watching some videos and what Bb has told me here. If any of this is not right please let me know. Also if you can think of anything to add I sure would appreciate.
> 
> 1. Connect gauges to system (engine off)
> 2. (If LOW READING both sides)
> ...


 I figured I would put my 2 cents in there.:vs_cool:


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## Brainbucket (Mar 30, 2015)

BigJim said:


> Question, normal readings are 20-30 low side and 200-300 high side. Here is a chart I found, does this apply to auto AC and home AC or just one of them:
> 
> Microsoft Word don't post right so I took a picture of the chart:


That's a general Vehicle A/C chart. But if we are going that route that you have to add sun load, and other stuff. Can't go by that as much as what you are reading. If it's hot outside, I put a big fan in front of condenser and go from there. You want to create the conditions the vehicle has when it's operating on the road.:vs_cool:


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## BigJim (Sep 2, 2008)

Thanks a lot 47, I will put that in my notes, that is really good to know. I have to go over things several times before it starts to stick. 

Bb, once again you, have gone far above and beyond in helping, I am sure there are others reading this and will get a whole lot from it as well as me, I can't thank you enough.

I read all I can find and last night I found a page at agcoauto.com that has tons of information, a lot of which Bb has already told me. One thing that stood out for me was the second paragraph of this:

_Start the engine and turn on the air conditioner. Actual readings will vary according to ambient temperature. The low-side should be near 30 PSI at 90 degrees Fahrenheit or less. Pressure that is too much lower or higher shows there is a problem.

On a properly working system, high-side pressure will be about twice the ambient temperature, plus 50 PSI. For instance, on a 90-degree Fahrenheit day, twice 90 is 180, plus 50 equals 230 PSI. This is not precise but close enough for the purposes of this article. Both pressures reading within these ranges means the system should produce a vent temperature in the mid, to low forties, with the engine idling._

I have another concern right now, unrelated to this. When I hooked up my gauges for the first time, I forgot to purge my hoses and I am sure I put air into the system. Is there a way to remove that air? Or will it be ok to just leave it in there?

Another question, when a system is evacuated, does the compressor oil dump also, or is there a separate operation to remove the compressor oil. 

My next project is to make or buy a recovery container and buy a fairly good vacuum pump.


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## Brainbucket (Mar 30, 2015)

47_47 said:


> It's been a long time but step 3, low and high side pressures should be the same and equal to ambient air temp (F) for a fully charged system.


I don't know about that. Generally the pressures are higher when outside temps are higher. when it's 50 degrees outside the pressures are still higher than 50 psi. But I will check that out. But sitting here thinking bout that, I don't agree.:vs_cool:


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## BigJim (Sep 2, 2008)

Brainbucket said:


> That's a general Vehicle A/C chart. But if we are going that route that you have to add sun load, and other stuff. Can't go by that as much as what you are reading. If it's hot outside, I put a big fan in front of condenser and go from there. You want to create the conditions the vehicle has when it's operating on the road.:vs_cool:


:surprise: I think I will forget the chart, that is too much for my ole brain to soak up. That does make perfect sense to try to create the conditions on the road.


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## Brainbucket (Mar 30, 2015)

BigJim said:


> Thanks a lot 47, I will put that in my notes, that is really good to know. I have to go over things several times before it starts to stick.
> 
> Bb, once again you, have gone far above and beyond in helping, I am sure there are others reading this and will get a whole lot from it as well as me, I can't thank you enough.
> 
> ...


The recovery systems are expensive. The vacuum pumps aren't.:vs_cool:


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## BigJim (Sep 2, 2008)

Thanks ever so much again Bb, that is really good to know by someone who does this type of work and knows what works and what don't. You are a wealth of information.


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## BayouRunner (Feb 5, 2016)

If you weigh the charge you can eliminate all that guessing. Put a scale on your shopping list too lol


Sent from my iPhone using Tapatalk


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## BigJim (Sep 2, 2008)

I found out something today, sitting at a computer checking out AC gauges is 100% different from actually doing the work. I did make one call right today, our Daughter's 2002 VW Jetta is totally empty of Freon both high and low side read dead Zero.

I also tried to figure out our grandson't 2005 KIA Optima today, I still can't figure it out. First of all I can not get the blower inside to work at all. I need to find how to jump to see if the inside blower motor is OK. The compressor does kick in for a few seconds then kicks out for a good while.

I hooked up the gauges and with the compressor running the low side was around 20, the high side read 175. The car not running, the gauges read LS 55, HS 120. I put some Freon in and the reading is now with compressor running, low side 30, high side 160.

I am now looking to see how to check the blower then go from there. AC is NOT as easy as it looks on paper.


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## BayouRunner (Feb 5, 2016)

Pressures will read low if the blower is not running. Chances are the unit is overcharged now. Blower has to be running to check charge. I'd start by checking and seeing if your blower motor is getting power. If it isn't, I won't be much help on the cars.


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## BigJim (Sep 2, 2008)

BayouRunner said:


> Pressures will read low if the blower is not running. Chances are the unit is overcharged now. Blower has to be running to check charge. I'd start by checking and seeing if your blower motor is getting power. If it isn't, I won't be much help on the cars.


After I put the Freon in I got to thinking that I may have done just what you said. My next move will be to see if I can jump the blower motor to see if it does work or not. Thanks BR, I appreciate it.


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## beenthere (Oct 11, 2008)

Yeah, adding charge on a unit that doesn't have the inside blower running, is never the thing to do.


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## BigJim (Sep 2, 2008)

beenthere said:


> Yeah, adding charge on a unit that doesn't have the inside blower running, is never the thing to do.


I texted him and told him to not turn the unit back on until we could get the blower working, I got a feeling that I really goofed.

I have narrowed it down to either the blower resistor or the blower motor. I have looked all over the net trying to find what the resistance from what pin to what pin of the resistor is and so far no luck. I have power to the switches but not to the blower.

If a unit is dead empty how do you find the leak without recharging the unit with freon? I know I will have to pull a vacuum on it. Another question, when I pull a vacuum does all the oil stay in the unit? I think it does because there is no place for it to go, right?


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## beenthere (Oct 11, 2008)

BigJim said:


> I texted him and told him to not turn the unit back on until we could get the blower working, I got a feeling that I really goofed.
> 
> I have narrowed it down to either the blower resistor or the blower motor. I have looked all over the net trying to find what the resistance from what pin to what pin of the resistor is and so far no luck. I have power to the switches but not to the blower.
> 
> ...


The oil will stay in the compressor.


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## BigJim (Sep 2, 2008)

Thanks BT, I appreciate that information.


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