# Trane XR90 - 3 Red Lights



## Tom Scott

Hi
I was hoping someone could help me. I have a 6 year old Trane XR90 Furnace that blinks 3 red lights when it calls for heat, then it shuts down.
3 Red Lights means “Pressure Switch Error”. 



This is what I have tried to fix this.


·  I have unhooked the hose that runs from the switch to the gas valve and to the burner box and cleaned the hose. I have also cleaned the barb the sticks out of the burner box.
· I have checked all the clear drain hoses in the furnace to make sure they are attached and not pooling water.
· I have checked my outside vent – it is not blocked and it exhausts when the furnace runs.
· I have installed a new furnace filter.


Here is some history. This has happened in the past (last year and the year before if I rember right) abd cleaning the barb helped, cause after I cleaned the barb form the burner box when I hooked the hoses back up the furnace worked.


This is not the original pressure switch. When it was under warranty I put a service call in and the first tech that came changed the switch out. But the next tech that came the day later because that didn’t fix the problem found the problem to be the outside vent was iced over. Not sure it this means anything or not just wanted to add it.


Now the weird part, right now the furnace works fine (cycles fine) when the hose that runs from the switch to the burner box is unplugged. But soon as I plug it in it will call for heat and shut down and blink 3 times.


Can anyone help me? Any ideas what is going on?


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## Doc Holliday

You're saying with the hose completey off thus removing the pressure switch's ability to close (which is the proper sequence of operation) which allows a furnace to run, it's running?

You can also clean the barb on the pressure switch. SPIN FAN SLOWLY WHILE CLEANING BARB/PORT FOR HOSE ON THE INDUCER. And with the hose on the pressure switch but off of the inducer, suck on the hose and listen for the click, meaning it's closing. 

Inducer motor may be getting weak and not closing the pressure switch.


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## Tom Scott

Doc Holliday said:


> You're saying with the hose completey off thus removing the pressure switch's ability to close (which is the proper sequence of operation) which allows a furnace to run, it's running?
> 
> You can also clean the barb on the pressure switch. SPIN FAN SLOWLY WHILE CLEANING BARB/PORT FOR HOSE ON THE INDUCER. And with the hose on the pressure switch but off of the inducer, suck on the hose and listen for the click, meaning it's closing.
> 
> Inducer motor may be getting weak and not closing the pressure switch.


 Thanks for your reply.

Yes, with the hose off, the furnace runs fine. That's how it is running right now. I am not comfortable with it, but I need a warm house.

I have tried cleaning the barb on the switch by sticking a paper clip in and out a few times. I have sucked on the hose with it attached to the switch and I do hear it closing. Also when I stuck a paper clip in I pressed it and heard a click as well.

The only part of your reply I am not sure of is the hose to the inducer. Is the inducer the black fan/motor to the right of the switch and under the burner box that vents up and out? I don't remember there being any hoses or barbs on that unit. I am at work now but I will look and try when I get home. 

The only hose I have cleaned and that is unhooked right now is the one that run from the switch to the burner box (and there is a T in the middle of it and a hose that runs to the gas valve vent).

If it is a weak inducer motor is there any possible fix for this besides a replacement? Like, could there be a belt or pulley slipping or would a furnace cleaning help?


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## Doc Holliday

Yes, the inducer motor is the what vents the exhaust fumes out through the metal flu pipe. The hose should be attached from said motor to pressure switch. I'm not sure what this 'T' is you're speaking of is. Can you take some pictures?

From here it sounds as if someone has bypassed something.


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## Doc Holliday

See the hose from the inducer to the switch?


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## harleyrider

Tom Scott said:


> Hi
> I was hoping someone could help me. I have a 6 year old Trane XR90 Furnace that blinks 3 red lights when it calls for heat, then it shuts down.
> 3 Red Lights means “Pressure Switch Error”.
> 
> 
> 
> This is what I have tried to fix this.
> 
> 
> · I have unhooked the hose that runs from the switch to the gas valve and to the burner box and cleaned the hose. I have also cleaned the barb the sticks out of the burner box.
> · I have checked all the clear drain hoses in the furnace to make sure they are attached and not pooling water.
> · I have checked my outside vent – it is not blocked and it exhausts when the furnace runs.
> · I have installed a new furnace filter.
> 
> 
> Here is some history. This has happened in the past (last year and the year before if I rember right) abd cleaning the barb helped, cause after I cleaned the barb form the burner box when I hooked the hoses back up the furnace worked.
> 
> 
> This is not the original pressure switch. When it was under warranty I put a service call in and the first tech that came changed the switch out. But the next tech that came the day later because that didn’t fix the problem found the problem to be the outside vent was iced over. Not sure it this means anything or not just wanted to add it.
> 
> 
> Now the weird part, right now the furnace works fine (cycles fine) when the hose that runs from the switch to the burner box is unplugged. But soon as I plug it in it will call for heat and shut down and blink 3 times.
> 
> 
> Can anyone help me? Any ideas what is going on?


You have a plugged intake pipe..........DO NOT OPERATE THIS UNIT UNTIL THIS CONDITION IS CORRECTED!!!!!!


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## Doc Holliday

Geez Harley, you could've warned us to put on some shades... :laughing:


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## Tom Scott

Doc Holliday said:


> See the hose from the inducer to the switch?


 Mine does not look like this - I will take some pictures and post.

If it exhausts fine, how could the intake be plugged? On the outside of the house it all comes in/out one/the same vent. The pressure is really good on the exhaust and looking in I did not see anything blocking it….


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## harleyrider

Tom Scott said:


> Mine does not look like this - I will take some pictures and post.
> 
> If it exhausts fine, how could the intake be plugged? On the outside of the house it all comes in/out one/the same vent. The pressure is really good on the exhaust and looking in I did not see anything blocking it….


its either the intake or the drain...........removing that tube is no different then by-passing a tripped limit......you are risking possible ,fire, carbon monoxide poisoning and death by tampering with that hose., take my advise and shut that unit down and get a pro out there.It could be a bad switch, but they rarely fail.


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## Tom Scott

Here is a picture


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## Tom Scott

Well this is starting to look like a call to a tech.
I have C0 detectors installed on all levels of my home or I wouldn't even run it like this


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## Doc Holliday

Check that run capacitor on inducer motor.


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## Tom Scott

Doc Holliday said:


> Check that run capacitor on inducer motor.


Is that the thing on the top left or bottom right on the motor and how do I check it?


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## Doc Holliday

Left. Silver can looking thing with two wires on it. Need meter with mfd or just remove it and take with u to Grainger. Ten buck part.


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## Doc Holliday

Bottom right is 120 volt feed to inducer from board.


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## Tom Scott

Doc Holliday said:


> Left. Silver can looking thing with two wires on it. Need meter with mfd or just remove it and take with u to Grainger. Ten buck part.


What voltage should it read if it's working properly?

Sorry for the the questions and thanks for your help.


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## Doc Holliday

Tom Scott said:


> What voltage should it read if it's working properly?
> 
> Sorry for the the questions and thanks for your help.


 
It's stated on the cap itself what the operating voltages should be but more importantly than what voltage it's holding is the microfarad it's putting out. As well, the mfd (uf) number is stamped on the cap.


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## raylo32

Unless I missed it one theing the OP never mentioned was whether inducer motor was running or not. That would be a useful data point.


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## Tom Scott

raylo32 said:


> Unless I missed it one theing the OP never mentioned was whether inducer motor was running or not. That would be a useful data point.


It runs.

Update. I have called for help and the first 3 companies I called said they are booking for next week. Finnally I got a someone and I am jsut waiting around for him now. I just hope he knows this model.....


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## NitrNate

the confusing thing is that from what you are saying, the unit is running and functioning properly with the hose detached from the pressure switch. the only thing i can deduct from that is that the pressure switch is somehow "stuck" in the closed position, because without a vacuum it would stay open and thus disable the unit. removing the hose under normal operating conditions would cause the unit to NOT run. if it IS running, i would think the pressure switch was the obvious problem.


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## hvactech126

an XR 90 would have a dual port pressure switch, if it runs with a hose disconnected that must be on the burner box side. check your intake, exhaust, and condensate trap. Remove the trap and run water through both sides until it runs clear.


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## harleyrider

NitroNate said:


> the confusing thing is that from what you are saying, the unit is running and functioning properly with the hose detached from the pressure switch. the only thing i can deduct from that is that the pressure switch is somehow "stuck" in the closed position, because without a vacuum it would stay open and thus disable the unit. removing the hose under normal operating conditions would cause the unit to NOT run. if it IS running, i would think the pressure switch was the obvious problem.


its not confusing at all.............the hose that is detached monitors the burner box for proper air flow for combustion.......take of the hose and take away the control boards ability to monitor the intake air.........hence a plugged intake...............i would be a dollar that if he put the hose back on, and took the burner box door off it would run as well.......if you have spare time.......check the cap.............


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## beenthere

Hmmm hmmm hmmm.

Can't we all just get along.

Post have been removed. Lets keep it friendly.


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## Tom Scott

hvactech126 said:


> an XR 90 would have a dual port pressure switch, if it runs with a hose disconnected that must be on the burner box side. check your intake, exhaust, and condensate trap. Remove the trap and run water through both sides until it runs clear.


Thanks, where is the trap?


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## Tom Scott

Nevermind the guy is here and it looks like it's draining fine.


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## Doc Holliday

beenthere said:


> Hmmm hmmm hmmm.
> 
> Can't we all just get along.
> 
> Post have been removed. Lets keep it friendly.


 
Party pooper. 

You know me, blood and broken bones is right up my alley. 

Thanks.


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## harleyrider

the trap is easy to find, follow the condensate hoses into the blower area.....its white with 2 5/16 screws holding it in place.two clamps hold the hoses on......when i clean these i submerge them in a bucket of bleach/water (as hot as you can stand) along with the hoses, as they too can get a build up in them. the off white fitting attached to the base of the combustion motor is another well know choke point on trains, so remove and clean this fitting as well.

after saying all this I do not think that its a trap issue......but what I described is good annually maintenance.


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## harleyrider

Tom Scott said:


> Nevermind the guy is here and it looks like it's draining fine.


please let us know what he finds............


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## Tom Scott

harleyrider said:


> please let us know what he finds............


Tested it with a new pressure switch and he gets the same thing. Hes calling his boss now.


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## beenthere

Clogged/restricted pressure hose. Restricted exhaust or combustion air intake pipe. Corrosion build up on hose pressure ports. Restricted drain line. Crack in a pressure hose. Slow spinning inducer. Cracked heat exchanger. loose restricter plate on the back of the inducer.

The tech should use a manometer and see how much pressure the switch is seeing.


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## harleyrider

Tom Scott said:


> He's confussed. Tested it with a new pressure switch and he gets the same thing. Hes calling his boss now.


 should of asked for the older more experienced guy.......


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## Tom Scott

beenthere said:


> Clogged/restricted pressure hose. Restricted exhaust or combustion air intake pipe. Corrosion build up on hose pressure ports. Restricted drain line. Crack in a pressure hose. Slow spinning inducer. Cracked heat exchanger. loose restricter plate on the back of the inducer.
> 
> The tech should use a manometer and see how much pressure the switch is seeing.


He has a fancy meter hooked up to the burner box now where the hose to the switch usually runs - I thinks hes testing the pressure.


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## Tom Scott

meter shows negative pressure out of the burner box.


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## harleyrider

Tom Scott said:


> He said the meter shows negative pressure out of the burner box.
> 
> But he admits hes confussed and frustrated.
> 
> Now he is taking off the intake pipe that is above the burner box....


 ta-da!!!!!


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## Tom Scott

It runs with the burner box open and the pressure swtich hoses hooked up properly.

Looking like an intake problem maybe, he thinks there might be a blockage.


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## Tom Scott

harleyrider said:


> should of asked for the older more experienced guy.......


I asked for an expierenced guy and told them I would call a different comapny if they did not know ho to service this model.


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## harleyrider

post #22


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## beenthere

Is it making a gurgling sound when its burning?


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## Tom Scott

beenthere said:


> Is it making a gurgling sound when its burning?


not that I hear


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## harleyrider

Tom Scott said:


> I asked for an expierenced guy, this is what they sent me


 the good thing is he is getting valuable experence...........on your dime


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## harleyrider

we tallked earlier about the trap......have him clean it while he is there.....


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## Tom Scott

harleyrider said:


> the good thing is he is getting valuable experence...........on your dime


lol - thanks that makes me feel so much better.


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## harleyrider

Well Tom, whats the verdict?


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## Tom Scott

Update

He left and I am right back where I started.

He wants to come back tomorrow after he talks to the manufacturer and get their advice.

Another guy came over and they both checked everything they thought might be the cause but found nothing but maybe something is in the intake pipe.

He wants to come back tomorrow and cut the intake pipe to look into it to see if its blocked.

The other guy read thru the install manual and said there is too many bends in the pipe that make the overall pipe length 10 feet too long based on the install manual and maybe that’s the problem.

They also said the inducer motor is at .5 something and the book said it should be .7
Right now they left it running with the burner box open just a crack and the hoses hooked up to the pressure switch because it runs that way with no error.

So that’s it for now.


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## harleyrider

tom send me a private message............i want to give you my cell so you can call me


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## Marty S.

Tom Scott said:


> It runs with the burner box open and the pressure swtich hoses hooked up properly.
> 
> Looking like an intake problem maybe, he thinks there might be a blockage.


Sure looks like a blocked intake pipe from here. A snake from the outside and shop vac blowing from the inside will have it cleared in no time.


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## Tom Scott

harleyrider said:


> tom send me a private message............i want to give you my cell so you can call me


tried to pm you, says I need 20 posts t osend a pm and I am at 18 now, I need to post a few more times


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## Tom Scott

now I tried and got this:

"harleyrider has chosen not to receive private messages or may not be allowed to receive private messages. Therefore you may not send your message to him/her."


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## Doc Holliday

Hundreds.


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## harleyrider

Tom here it is........

http://www.youtube.com/watch?v=LyPm8d9g-tE


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## harleyrider

tom.....here is part two...........american standard and trane are the exact same thing

http://www.youtube.com/watch?v=GYOSH0M-xt4&feature=related


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## harleyrider

part 3


http://www.youtube.com/watch?v=6oS4IQYrNZE&feature=related


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## harleyrider

and finally part 4

http://www.youtube.com/watch?v=qmaT07ho3A4&feature=related


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## Doc Holliday

Those seem like good, informative vids. I watched part one so far. I'll watch the rest tomorrow. 

Is that you hrider? Your company?


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## harleyrider

Tom as you watch these short video's they will all seem Greek to you, but when them guys get back out there on Wednesday I would insist that they watch these video's if they still cant find a definite problem with the intake pipe.

I have personally done this repair over a hundred times in the last 7 or 8 years, hopefully your unit is still under warranty. please let me/us know how it turns out.


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## harleyrider

Doc Holliday said:


> Those seem like good, informative vids. I watched part one so far. I'll watch the rest tomorrow.
> 
> Is that you hrider? Your company?


 
No, but as I stated in a previous post I did over a hundred of these in the last 7 or 8 years.


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## Doc Holliday

harleyrider said:


> No, but as I stated in a previous post I did over a hundred of these in the last 7 or 8 years.


 
I just read another thread where you said you've been in the trade for 30 years. That guy in the vid might only be in his early thirties so unless you were two or three years old when you started... :laughing: Got it. 

Good videos, I've now watched the first two parts. I've seen plenty of cracked exchangers but I haven't spent much time on condensing units so thanks for posting those.


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## Tom Scott

harleyrider said:


> and finally part 4
> 
> http://www.youtube.com/watch?v=qmaT07ho3A4&feature=related



Thank You


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## raylo32

Great vids you linked, rider. Very educational. Looks like that is where this one might be heading...


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## harleyrider

raylo32 said:


> Great vids you linked, rider. Very educational. Looks like that is where this one might be heading...


Yes I am afraid so, if that intake is clear, this is the most probable culprit. Here in the states Trane did a very aggressive Dealer notification to make them aware of the issue, and a lot of supply houses even repaired the units affected before they were sold. Trane deemed the problem "solved" in late 08. Obviously since I repaired over 100 myself and many more keep popping up all over North America, (this one is in Alberta Canada) they let a few slip through the cracks......


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## raylo32

No pun intended?? ;-)




harleyrider said:


> Obviously since I repaired over 100 myself and many more keep popping up all over North America, (this one is in Alberta Canada) they let a few slip through the ***cracks***......


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## Tom Scott

OK, the guys came back today. The poured 2 buckets of water down the exhaust pipe from the outside and they said it looked like there was a problem in the collector box with the drainage.
They didn't bother video snaking the intake because they said they called Trane and they told them it probably wasn't that.

Then they left and called Trane. Trane told them to tell me to call the people who installed it because it might be a warranty job they (they guys I called) were not authorized to do this repair. 

But first i am going to try and clean the trap and that other part Harley mentioned in his post to clean besides the trap and if no luck I will call the original installer, who I had actually called first but they told me it was a week wait.

So really I am back where I was when this started.


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## harleyrider

Tom Scott said:


> OK, the guys came back today. The poured 2 buckets of water down the exhaust pipe from the outside and they said it looked like there was a problem in the collector box with the drainage.
> They didn't bother video snaking the intake because they said they called Trane and they told them it probably wasn't that.
> 
> Then they left and called Trane. Trane told them to tell me to call the people who installed it because it might be a warranty job they (they guys I called) were not authorized to do this repair.
> 
> But first i am going to try and clean the trap and that other part Harley mentioned in his post to clean besides the trap and if no luck I will call the original installer, who I had actually called first but they told me it was a week wait.
> 
> So really I am back where I was when this started.


 
I am convinced that its the heat exchanger, same problem as in the video's.....Tom you can call ANY Trane dealer, it does not have to be the original ones that installed it. Do you know when they poured the water in, did it run out in the blower compartment? Please keep us posted


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## Tom Scott

harleyrider said:


> I am convinced that its the heat exchanger, same problem as in the video's.....Tom you can call ANY Trane dealer, it does not have to be the original ones that installed it. Do you know when they poured the water in, did it run out in the blower compartment? Please keep us posted


Will do.

Thanks again for the help & advice.


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## beenthere

I always call tech support while I'm at the job site. Don't always get through, but 98% of the time I do.

Tech support always wants this that and the other thing checked. And generally ask the techs to do this while they are on the phone with them.

Don't know why anyone would leave a customers house and then call tech support.


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## Tom Scott

Spoke to my installing dealer and told them what the other guys did and they want to order a "cold header". This is before they even look at it, just by what I told them (the other guys tested the switch, inducer and exhaust).

I just find it a little odd that no one wants to examine the intake pipe.


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## harleyrider

Thats OK Tom, let them swap out your heat exchanger (its made in an era were they were known to fail ) then if/when it still doesn't work then they can check the pipe......:thumbup:. If the pipe is accessible, you can "X-RAY" it by holding a bright light on 1 side, and anything in the pipe will cast a dark shadow on the other side of the pipe. Its not fool proof, but i have used it in the past to find tennis balls, sand from the sand box and dead chipmunks.


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## Tom Scott

harleyrider said:


> Thats OK Tom, let them swap out your heat exchanger (its made in an era were they were known to fail ) then if/when it still doesn't work then they can check the pipe......:thumbup:. If the pipe is accessible, you can "X-RAY" it by holding a bright light on 1 side, and anything in the pipe will cast a dark shadow on the other side of the pipe. Its not fool proof, but i have used it in the past to find tennis balls, sand from the sand box and dead chipmunks.


 I think they are only ordering the "Cold Header" - I am under the impression this isn’t the entire heat exchanger. The service manager called me back and he seemed to know what he was talking about, but I think he is calling the cold header the transition piece from those videos. At least it's under warranty, just not the labour.


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## harleyrider

They don't send just the "cold header" you are getting a whole heat exchanger.


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## Tom Scott

For anyone who cares, here is an update on this.

Today, the job was finally completed.

A couple of weeks ago they guy came with just the transition piece (plastic part between the inducer and the 2nd heat exchanger). The screws from the factory cracked it. But it was really obvious more was need as once he took off the inducer we could see lots of rust and corrosion and a crack from the dripping corrosion on the front plate of the 2nd heat exchanger. So we still had a code 3 after the part was installed.

So today he came back with the entire heat exchanger and installed it and so far everything seems to be running fine.

I just wanted to thank everyone who posted advice and especially thank HarleyRider. Your advice was spot on and invaluable, it really helped me a lot on dealing with this.

Cheers!


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## harleyrider

Glad it all worked out, and by now you almost have a new furnace again....what you was witness to early on in this problem, is a problem we are dealing with nation wide......unskilled techs that seem to refuse to pay attention to the obvious.As well as company not requiring the owner ship of essential tools such as digital manomators, gas pressure gages and thermistors for measuring temperatures.

Most of these kids now a days want to read a blinking red light change a part, and make $30 dollars an hour.Thats just not going to happen. Thats why i stress always insist on the older guy, with all the proper tools when calling for service.

They dident charge me a penny for the international call either.......lol


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## no7or

Thanks for the tips guys. I was able to save myself a huge repair bill by following your collective advice. I checked and cleaned the P-Trap, checked my pressure switch, all seemed ok. My furnace is mounted horizontally in the attic crawl space and vented almost directly above through the roof. SO take the tubing off at the burner plenum and the furnace starts and runs. Take the cover off the burner plenum and find several small wasp bodies! check the air inlet screen, and viola, found their nest sucked in. Cleaned everything up and reassembled, furnace started properly!


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## no7or

Just an update, I had cleaned everything, thought it to be good, and it stopped yet again overnight. I called one of our local guys, he found the multi wire connector at the circuit board could be moved ever so slightly and cause the furnace to fail or start depending on position. Since I am an electronics technician I am familiar with this issue on other equipment, so going to let the house warm up then remove the circuit board and resolder the connector. A $68 service call but I hadn't and probably would never have thought to check that connector.


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## dr3

Morning all - Good news I had the 3 blinking lights and did the steps below to clear the issue.
Clean the input pipe screen at the center of the unit where the PVC input pipe is. Lots of bug shells and junk clogging the input.
Take off the burner cover and vacuum the inside nice. this is on the other isde of the input pipe and you take four screws off
Run some hot water into the output vent pipe to clear and ensure the drain pipes are good.
Clean and remove the water pipe collector piece and wash out the gunga inside.

seems like this is good maintenance and it only took an hour or so. Good luck out there


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