# So I want to replace the contactor in my outside unit



## sarahWW (Jul 12, 2012)

I ordered a replacement contactor for about 20 bucks. The new part was the same manufacturer, but was the suggested "replacement" for the original part (which was a Honeywell R8242A 1271). The part that arrived is not the same though. It's a "mirror twin". So obviously I can't just swap out the wires one by one and be done. 

What is the best way to manage the new wiring? Should I install the new contactor upside down so that all the wires reach? Attempt to drag wires to the opposite side of their former positon? Try to find old stock of the part? 

Here is the new part

I will try to attach a pic of the old one, still wired up: (well shoot, it wont let me upload a file) Since I cant do that, just imagine the one above in mirror image.


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## scottmcd9999 (Jun 29, 2012)

First: Why do you want to replace your contactor? They don't typically wear out ...

Yes, you can just turn the contactor upside down. They are not position sensitive.


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## sarahWW (Jul 12, 2012)

I want to replace the contractor, because the contacts are burned on one side, and when the condenser gets the signal to turn on, the contractor rapidly opens and closes; rather "chatters" - Ka thunk Ka thunk Ka thunks Ka thunk.


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## biggles (Jan 1, 2008)

might of been a weak coil or the 24V out from the furnace/stat.don't know what a mirror twin is?the one you show is a single pole contactor can't get any smaller.shut the disconnect off mount the wires exactly one at a time NOTE T side is load fan/comp...L side is disconnect into the contact...all the wires connected mount the contactor in the middle of the wires so none pull from either side...do the line wires first both sides...then the 24V pair


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## ben's plumbing (Oct 6, 2011)

sarahWW said:


> I want to replace the contractor, because the contacts are burned on one side, and when the condenser gets the signal to turn on, the contractor rapidly opens and closes; rather "chatters" - Ka thunk Ka thunk Ka thunks Ka thunk.


 you could try filing it down 1st....shut off power to unit and file down burnt contact as good as you can then try it..worked for me many times....:yes:


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## sarahWW (Jul 12, 2012)

The link above, in my top post, is to a picture of the replacement contactor on the vendor's page.

I am trying again to attach a photo of the current (0ld) contactor as it was wired into my unit, but the pic is too big. I have to tweak it, will be back in a few


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## sarahWW (Jul 12, 2012)

Here is a pic of the old contactor, with all the old connections.


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## scottmcd9999 (Jun 29, 2012)

That's not a mirror twin, it's an exact replacement. It mounts the same way, has the same terminal layout, and should cross over exactly. Don't be concerned with the terminal "designations" - i.e. the L and T designations - just match up the contactor in the same orientation as the original and swap it wire for wire.

I too have fixed some contactors by removing the contacts and filing them down, but it's tricky to do (that #[email protected]% little spring is tough to catch sometimes) - and for 20 bucks it's not worth the hassle!


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## sarahWW (Jul 12, 2012)

At the vendors page, you can see the part I bought to replace it, per the site's recommendation that this one is a replacement for the one in my unit. All the wiring on the left side of the image of my original contactor, would have to be hooked up to the right side of the new part, if the contactors are oriented the same way. My plan was to get an identical part, and reproduce the positions of the wires exactly. 

I can't read electrical diagrams in a way that would help me place the wires, but can only copy what was there before. Which is the "T" side? In my picture of my old contactor, I am guessing it is the right side of the picture, and The black and red are the 24v pair.


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## sarahWW (Jul 12, 2012)

Scott, pardon my confusion, but on the old contactor, the two screws with little plates that hold down the black and red wires, and have screws of a different color are on the left side of the picture. If I orient the new contactor the same way, the two screws with little plates that are a different color would be on the right. They don't match in appearance, but if I held the old one up to a mirror it would look the same as the new one.

Are you saying it doesn't matter which side has the coppery looking screws with the little plates?


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## scottmcd9999 (Jun 29, 2012)

> All the wiring on the left side of the image of my original contactor, would have to be hooked up to the right side of the new part


No, you shouldn't do that. The terminal designations on the contactor are meaningless (the original contactor looks to have OEM markings on it, which would not be reproduced on the Honeywell version).

Looking at your two images, with the terminals from the OLD contactor noted first:

11 >> T1
12??) >> L1 
23 (L) >> T2
23 (R) >> L2

I can't really read the number on the original image, on the top right side, so just assume it said 12.


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## scottmcd9999 (Jun 29, 2012)

> Are you saying it doesn't matter which side has the coppery looking screws with the little plates?


Yes, exactly - and in fact, you can swap the those hold-down plates to either end. Just back them out (the screw and all) and swap them with the screws on the other end.


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## sarahWW (Jul 12, 2012)

Hurray! Since I was relying on copying the placement of the wires and everything looking exactly the same, I did not want to take chances with the swap. Thank you for cluing me in.

Biggles, I was wondering if the transformer might be the root of my troubles. FWIW the AC in my house is in the attic, the boiler for my hot-water baseboard heat in the basement. The thermostat, however is wired so that it controls both cooling and heating, and allows me to run the continuous fan in the attic air handler in either mode.


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## turnermech (Jul 21, 2012)

sarahWW said:


> Hurray! Since I was relying on copying the placement of the wires and everything looking exactly the same, I did not want to take chances with the swap. Thank you for cluing me in.
> 
> Biggles, I was wondering if the transformer might be the root of my troubles. FWIW the AC in my house is in the attic, the boiler for my hot-water baseboard heat in the basement. The thermostat, however is wired so that it controls both cooling and heating, and allows me to run the continuous fan in the attic air handler in either mode.


your tstat uses isolated subase with a RC and RH terminals. This is the norm for your application. Fan control will come from the RC which is cooling transfromer in either mode (heating or cooling)


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## Yoyizit (Jul 11, 2008)

sarahWW said:


> the contractor rapidly opens and closes


This oscillation almost certainly is caused by a high resistance (say, 0.1 ohm) at the contacts or in the supply lines or in the ground wiring for the controls. 
The high line resistance could have caused the burned contacts but not the other way around.
Good luck.


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## sarahWW (Jul 12, 2012)

The contacts I thought perhaps burned from the frequent surges and power outages in my area recently, I'm confused about what you said about the contacts burning. Do you mean burned contacts could be causing the chattering but that burned contacts would not cause high line resistance?


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## Yoyizit (Jul 11, 2008)

High resistance somewhere could cause chattering.
Burned contacts may exhibit high resistance.
Contacts may burn because of relay chattering or old age.
Connections may become high resistance connections due to age or day/night temperature variations or incorrect install.
The connection resistance may vary with the current drawn or be constant.

It's like when your car solenoid oscillates because of a corroded battery connection.

You're looking for a connection that is supposed to carry heavy current.

You can check connection integrity with a DMM and a heavy resistive load rated for 240v and 10A or 20A but this procedure is a little bit beyond most DIYers.


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## sarahWW (Jul 12, 2012)

My replacement contractor is in place now. Sadly, it chattered on start up.
The compressor ran for one minute, then heard a sound I suspect is a bypass of some sort, and then rather loud compressor complaining motor noise. (I shut it off of course)

All the troubles began after a three week ordeal with two major power outages and then a horrible heat wave - the capacitor blew. It seemed to work fine after two power restorations, but conked in the heat wave. 

I thought the only problem that would need fixing was the capacitor. Service tech came out late on a Sunday. He only had two "spare" single caps of the right microfarads on the truck - but put in a dual capacitor the next day per my request. When he put in the single caps, the system seemed to start fine. Then as he was packing up, the contractor started opening and closing; its was very loud. On restart it smoothed out. He checked voltages and so forth and all was fine. He left with the system running. The service company called to put off the capacitor swap (for a new dual one) for a couple of days and I agreed. But I had to call them back:

Inside cool air seemed only to "ooze" out. The system then freaked out a couple of times. Once it cut out entirely, then restarted without issue. Then I found it with the fan going but no compressing going on, and just cool air blowing out of the top of the compressor. I turned the system off. 

Another guy comes out with the new capacitor. He puts it in. The system chatters for him too, on first start up, but smooths out. This time it runs great guns for about 24 hours. Lots of nice cold air and joy for all the inhabitants within. He was supposed to check pressures on this visit, but didn't because it was just working brilliantly.

Then, it just pooped out. I go outside, and find the compressor is running but not blowing hot air out of the top. 

On the third call the guy taking the pressures said the system was overcharged. The system pressures were "over the moon" - and higher on the low side. He said he'd never run into this problem before.


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## beenthere (Oct 11, 2008)

You may be having a line voltage problem from the transformer that serves your house. m ay want the power company to come out and check it.


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## Yoyizit (Jul 11, 2008)

sarahWW said:


> All the troubles began after a three week ordeal with two major power outages and then a horrible heat wave - the capacitor blew. It seemed to work fine after two power restorations, but conked in the heat wave.


There may be patterns of power quality problems that are especially harmful to HVAC equipment, e.g., rapid dropouts and restores.

The chattering smoothing out, if it was caused by a bad connection, implies self healing - what could that be about?

Your outage certainly opened a can of worms. I wonder if it totaled your AC. And how would you prove that?


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## sarahWW (Jul 12, 2012)

beenthere said:


> You may be having a line voltage problem from the transformer that serves your house. m ay want the power company to come out and check it.


Sorry to be slow to respond....but we lost power last evening, for about 12 hours. I know there was a broken pole in the area, though there wasn't any weather to directly cause such a thing. After the power went out there was a brief downpour, but loss of power preceded, there was no thunder, lightning, not even a stiff breeze. I speculate there was a transformer explosion, perhaps resulting from a surge.

I do want the power company to come check out the situation, especially since I've been reading other customers report some problems with some of the recent repairs.

One service tech did suggest voltage drops as a potential cause of trouble, though as I said, it "smoothed out"; his tests showed no abnormalities as he was observing, but he said it could be intermittent. When he left the system was working well and continued to work well for about 24 hours.


FWIW, I have no doubt we have dirty power in general in this area. I believe it has contributed to early deaths of other appliances over the years. And I think they have been "throttling" the power in the aftermath of outages in the intense heat wave.

I hope my AC isn't a total loss situation. I suspect it may be.


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## sarahWW (Jul 12, 2012)

I was thinking of a "hail mary" with a hard start capacitor, or even swapping out the recently replaced (by service company) capacitor with a spare I bought, in case that one wasn't REALLY new or took enough beating to fail or was weak after being on the shelf too long.

My coils aren't awful-looking but I thought I might wash out the outside. I'd clean the evaporator coil with self-rinsing foam if I could get everything running again, but otherwise won't bother.


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## biggles (Jan 1, 2008)

try this testing...shut the disconnect outside for the condenser then remove the stat off the subbase and jump R to Y.this is a direct jump for cooling that sends 24V constanly to that contactor..when you go out the contactor should bein(no fan.comp )with disconnect OFF:wink: leave it off.no break one of the low voltage wires coming into the condenser..so th contact open touch it it closes do it a dozen time open/closed...open/closed...again and again...i want to see if the transformer is weak from the 208V pole spike.. if i chatters with th wire touched push it in see if it stays? lets here back...eithet a loose connection or the control module with the stat inline(jump removes that load) is draining the VA on that furnace TR..easy fix...see if you have a local GRAINGER around..what type of stat are you running solid stat LED type? 40/50/60-VA....115V-208V-24V check all connections on the low voltage side and stat terminals... http://www.grainger.com/Grainger/WHITERODGERS-Transformer-6WU91?BaseItem=3TZ67


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## Yoyizit (Jul 11, 2008)

Your predicament brings up some ideas.

For $20 in parts (a "window comparator" and LM555 timer) a device could be wired into your power line and thermostat that would shut off your AC within 0.015 seconds when it detects an out of bound voltage and then waits a minute or 10 minutes until the power surge is gone.

For considerably more than $20 you add a neural network that learns the pattern of your Poco's glitches and turns off your AC in anticipation of a glitch.
You could have it wired into one of these detectors that detects nearby lightning strikes for additional security.

This is all existing technology. If the market demand is there some company may already make these things. Searching patents online may be a good place to start.

Or you may be able to get insurance against these kinds of things. These events are not exactly "Acts of God" and insurance companies know how likely it is that your Poco will wreck your appliances in your area.


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## sarahWW (Jul 12, 2012)

Yoyizit said:


> Your predicament brings up some ideas.
> 
> For $20 in parts (a "window comparator" and LM555 timer) a device could be wired into your power line and thermostat that would shut off your AC within 0.015 seconds when it detects an out of bound voltage and then waits a minute or 10 minutes until the power surge is gone.
> 
> ...


Interesting idea. Over the years I've wondered about some kind of whole-house surge protection but never seriously investigated the possibilities. We get dips, sometimes throttling, too. If I end up having to sink $ into altogether new system, it would only make sense to try an protect it given the fragility of our local grid.


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## sarahWW (Jul 12, 2012)

Biggles: 


I speak less HVAC "jive" than I'd like to.
I would like to try what you suggest, but might have to ask for some steps to be translated or to ask exactly how to do something. 
Would you be willing to describe things to someone who's not done much of this before, and talk me through it?
*
I can* capture pics and vid and post it here or link to youtube


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## biggles (Jan 1, 2008)

the reason for shutting the condenser disconnect is so your not banging it off/on checking that 24V control circuit being called in from the stat and furnace...the line voltage has nothing to do with the contactor action opening or closing out at the condenser.call the stat to cool and break the control wire at the contactor touch nd retouch it see if it chatters or holds..might need a new TR in the furnace?sorry for the ramble but that is how a service tech is when he is banging you for 
$200 repair plus unneeded parts.like he is doing magic...:wink:


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## sarahWW (Jul 12, 2012)

biggles said:


> the reason for shutting the condenser disconnect is so your not banging it off/on checking that 24V control circuit being called in from the stat and furnace...the line voltage has nothing to do with the contactor action opening or closing out at the condenser.call the stat to cool and break the control wire at the contactor touch nd retouch it see if it chatters or holds..might need a new TR in the furnace?sorry for the ramble but that is how a service tech is when he is banging you for
> $200 repair plus unneeded parts.like he is doing magic...:wink:



There are terms I don't know the shorthand for. Does "stat" refer to the t-stat, or some other control? Also, what is TR shorthand for? I don't recognize the abbreviation.

My furnace isn't a furnace - I have a boiler separate from the AC (hot water baseboard heat), though they share the thermostat. I select cool or heat mode 

There is also relay in place that allows me to run the continuous fan mode in the air handler and the boiler at the same time.


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## scottmcd9999 (Jun 29, 2012)

Sounds like you've got an intermittent short somewhere, which is a very difficult thing to track down. 

You could also have troubles with logic boards, transformers, etc etc - in cases like this, you are often better off leaving this to a competent service company - although they will have a difficult time fixing a problem if it's not occurring during the visit.


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## sarahWW (Jul 12, 2012)

scottmcd9999 said:


> Sounds like you've got an intermittent short somewhere, which is a very difficult thing to track down.
> 
> You could also have troubles with logic boards, transformers, etc etc - in cases like this, you are often better off leaving this to a competent service company - although they will have a difficult time fixing a problem if it's not occurring during the visit.


Exactly, though the hourly diagnostic fee will be, like the last service tech described my "overcharging" system, "over the moon". Also my service company, sadly, is rather interested in getting me to replace my system. (Not until next year.) Any relatively simple tests or lower-cost part swaps that don't involve removing or adding refrigerant or blowtorches, I am willing to attempt.

Failing that, learning about what MIGHT have gone wrong and what will be tested, will help me deal with the service company, and understand what they tell me.


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## scottmcd9999 (Jun 29, 2012)

In cases like this, my short money is usually on the circuit boards (in the furnace, outdoor unit or tstat) followed closely by thermostat wiring to outdoor unit, followed by the transformer.

To test the tstat, just jump R to Y at the stat. If the unit comes on without chattering, you may have found your trouble. Put it back together, turn the system on, and next time it starts chattering you can then try jumping the R and Y leads AT THE AIR HANDLER (with the system on and running). if that stops the chattering, then chances are you've found the issue.

Hard to say with logic boards, since often they must be temporarily removed from the circuit and the items they control hardwired for testing. This can be tricky.

As to a transformer - you'd almost have to replace it with a known good one to eliminate that. Tformers are fairly cheap, of course, and generally fairly easy to get. 

I'd also isolate the boiler temporarily (i.e. remove the stat wires from there).


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## sarahWW (Jul 12, 2012)

scottmcd9999 said:


> In cases like this, my short money is usually on the circuit boards (in the furnace, outdoor unit or tstat) followed closely by thermostat wiring to outdoor unit, followed by the transformer.
> 
> To test the tstat, just jump R to Y at the stat. If the unit comes on without chattering, you may have found your trouble. Put it back together, turn the system on, and next time it starts chattering you can then try jumping the R and Y leads AT THE AIR HANDLER (with the system on and running). if that stops the chattering, then chances are you've found the issue.
> 
> ...


Would the circuit boards give *any* clues to failure via plain old eye-balling? I'm thinking I would have to rule out failure of other things and leave suspicion of the boards to last. 

Replacing the transformer would be one way to go. And the relay that is near the boiler in the basement could be easily replaced.

My AC is doing something else besides chattering. It runs oh so briefly (30 sec to 2 minutes), then the compressor seems to bypass and either makes an awful noise and hot air stops coming out of the top of the condenser unit, or just shuts off altogether. 

It is, I presume, overcharging.

I have seen some discussions elsewhere, and a hard start capacitor seemed to put things right in at least one similar case. 

I have to go up to the attic, and see for myself whether there is a thermal expansion valve.


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## scottmcd9999 (Jun 29, 2012)

> It runs oh so briefly (30 sec to 2 minutes), then the compressor seems to bypass and either makes an awful noise and hot air stops coming out of the top of the condenser unit, or just shuts off altogether.


This is caused by a restriction in the lines somewhere (most often in the condenser, or in the liquid line or drier). This is not something a DIYer can fix.

A hard start kit won't resolve either of these issues. 

Time to call out your contractor again.


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## sarahWW (Jul 12, 2012)

scottmcd9999 said:


> This is caused by a restriction in the lines somewhere (most often in the condenser, or in the liquid line or drier). This is not something a DIYer can fix.
> 
> A hard start kit won't resolve either of these issues.
> 
> Time to call out your contractor again.


My inclination is to call a new service co. at this point. My system worked great until it blew a cap; the banging and chattering was evident at first visit and the jerry-rigged single caps. It worked well for 24 hours after same banging situation (with intermittent voltage problem suggested). 

Third visit it just bypasses every time an attempt is made to start the unit.

A line restriction was suggested. 
Service tech took some refrigerant out (after making a big deal about service valve leaks -which btw secretly got my back up as, trust me on this one point, sealing the valve caps works FINE). He said pressures were high but wouldn't tell me the reading, and wouldn't write it down. He said it was high on the low side, too.

My unit may well have reached the end of it's mechanical life, but it is not getting replaced this year, so it's patch repair or nothing. 

What do do about a line restriction? What's the best way to tell if it's in the liquid line or elsewhere?


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## scottmcd9999 (Jun 29, 2012)

I wouldn't call the single caps "jerry-rigged". Before dual caps, that's what was installed - a separate cap for both fan and compressor.

Sometimes capacitors can take out other parts when they fail, especially compressor caps. Most caps don't fail the day they're replaced; they get weaker over time, forcing the motor they're connected with to work harder and harder. This puts a strain on the motor, and can destroy an already weak motor. That's not the fault of the service company.

However, it does sound as if you've lost faith in the company, so it would probably be best if you contacted someone else.

If it is a restriction in the liquid line, then it's most likely in a drier or in the expansion device. However, it could be in the condenser itself. The only way to tell is to take pressure and temperature readings on the liquid line, and see where that change of state is happening.


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## sarahWW (Jul 12, 2012)

scottmcd9999 said:


> ...(snip)
> 
> ...If it is a restriction in the liquid line, then it's most likely in a drier or in the expansion device. However, it could be in the condenser itself. The only way to tell is to take pressure and temperature readings on the liquid line, and see where that change of state is happening.


What would cause high pressures on the suction line AND high head pressures?

This situation seemed to puzzle the HVAC tech exceedingly. I don't know what the pressure readings actually were - and they aren't documented on the service slip either.


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## ben's plumbing (Oct 6, 2011)

sarahWW said:


> What would cause high pressures on the suction line AND high head pressures?
> 
> This situation seemed to puzzle the HVAC tech exceedingly. I don't know what the pressure readings actually were - and they aren't documented on the service slip either.


 here are a few causes of high pressure in the suction side.....restricted air..{condenser}...air and non condensables... overcharge....excessive air..{evaporator}....overfeeding metering device....bad valves {low amp draw}


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## ben's plumbing (Oct 6, 2011)

some causes of high head pressure,,,dirty condenser coils.....overcharged ..refrigerant flow restriction....extra hot indoor temperature...


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