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Old 05-07-2008, 09:46 AM   #1
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Compressor not running


I just replaced a condenser fan motor on my Lennox Hs19-311-2P because of a rusted out shaft that finally broke. When trying to get my A/C going, the condenser does not kick on. There is definetely 240v going into the unit, but the compressor contactor is not pulling on. I can manually push the contactor down and it will start the unit. Does anyone know what that contactor looks at in order to pull down. Any help would be greatly appreciated.

JR


Last edited by jackrod; 05-07-2008 at 11:24 AM.
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Old 05-07-2008, 04:52 PM   #2
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Compressor not running


The contactor pulls in using 24v from your furnace/air handler.

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Old 05-07-2008, 10:36 PM   #3
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Compressor not running


Thanks for the reply.

I will see if I am getting that voltage.

Could a leak have developed in my compressor(or damage to the compressor) if the unit was running without the cooling fan (I don't know how long it operated without the fan running).

Which in turn cause the contacter not to close because of a low pressure condition?

I don't see any low pressure switches in the wiring schematic. Just a high pressure switch.
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Old 05-07-2008, 11:25 PM   #4
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Compressor not running


Your high pressure switch may have opened and not reset itself due to your a/c running but no fan, you can try bypassing the switch for now to see if that is your problem, my guess is that it is.
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Old 05-08-2008, 11:38 AM   #5
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Compressor not running


Pressure switch is open, but also no 24vac from furnace..... Very fishy. How could a busted fan cause both of these to happen. I'm guessing that 24vac should start as soon as the A/C kicks on?
I waited at least 5 minutes, but still no voltage.
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Old 05-08-2008, 06:10 PM   #6
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Compressor not running


if the stat wire is tied to the pipe run out you might of tepped on it when you were involved with the condenser fan changeout...the pressure switch if HI MIGHT OF FATIGUED FROM CYCLING hi trip with the fan bad
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Old 05-08-2008, 09:36 PM   #7
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Compressor not running


check fuse on circuit board in air handler

check for 24 volts between terminals y and c on same circuit board

you may have grounded out the low voltage when wiring the fan to the contactor seeing as it does not lose power when the a/c disconnect is off.

if you do have power at the board, but not at the unit, then you have a problem with the field ran 2 wire. inspect it thoroughly.

as for the pressure switch being open.....jump for now and replace if necessary.

happy fixin
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Old 05-08-2008, 11:05 PM   #8
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Compressor not running


Before reading these posts, I looked at the 5 amp fuse. It is not blown. My 24vac wires are hooked up to B and Y on the board. I have not checked those directly,---(I just checked the outside wires) but I will. I'm not sure if there is a Y and C, but I will check those also.
I have a Trane XL90 Model number TUX080R942V1 furnace. I appreiciate all the help everyone is giving out. I am trying to do all this while watching my 4 year old and 2 year old during the morning hours and going to work in the evenings.

JR
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Old 05-09-2008, 04:32 PM   #9
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Compressor not running


Well, the 24vac magically appeared. I don't know what happened, but it is now there. Soo, I jumpered the high pressure switch and the A/C now works. Don't know how often it overpressures, or what kind of damage could be done, but that is how it is going to run for now. Hate to break into the system to change the switch, but eventually I will have to get someone to do it.

Thanks for all the input. Stay cool

JR
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Old 05-09-2008, 04:42 PM   #10
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Compressor not running


You can buy a high pressure switch that will screw onto your valve stem on the outside of the unit and wire it in that way. also get a tee fitting so manifold gauges can be hooked up if the charge ever needs checked. Alot easier fix than changing the switch that is brazed in the line.
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Old 05-09-2008, 04:44 PM   #11
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Compressor not running


Thank you. That sounds like an awesome idea!!!!
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Old 05-10-2008, 08:18 AM   #12
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Compressor not running


Just a follow up to the High pressure switch. While looking for a replacement switch, they were being called manual reset switches.
I was wondering why my pressure switch looked kind of weird, with that obvious nipple sticking out. Well, I pushed it in and presto. It reset. Works fine.
No wonder no one ever called me Mr. Obvious.
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Old 06-07-2008, 11:24 AM   #13
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Compressor not running


Please help... I admit it.... I'm a helpless chick...

I have a very old air conditioner (maybe 20 years old) but it has always worked so I saw (and still see) no reason to replace it. I turned it on last night and it worked fine thru the night. I have it set on an automatic thermostat that lets temp get warmer during the day when I'm usually out, but today I'm home so I turned the temp down and.... fan immediately started on outside A/C unit, as it always does, but blower in the house never kicked on. Finally, after a FULL half hour, I was just about to turn the AC off, thinking it would burn out or something, when poof, it clicked on and is working fine.

I don't usually pay any attention to how long the inside cold air usually takes to start blowing after I change the temperature or it automatically kicks on, but I'm sure it is NOT a full half hour!

Can anybody help me with some basic information? Could it be because it's so hot today in NJ (90s, humid)? Or does it mean my AC is going to fail soon? Is there something that can be done to help it? (Only problem/repair I ever had was a blown fuse (I think that's what it was, in a box outside, near the AC unit) many years ago.

Not only do I not want to spend the money to buy a new unit, but, frankly I'm feeling jaded about new appliances lately. My 2 month old Whirlpool dishwasher soap dispenser stopped opening after 1 month and they STILL can't fix it. The "diagnostics" run fine, so they tried changing the computer board, but that didn't help. Whirlpool says my warranty doesn't cover replacement, only repair, but has not yet answered my question... what happens if they can NEVER repair it? ... I'm afraid the real answer is... we jerk you around for 10 more months until your warranty expires. .... Sorry, just ranting. I'm just so frustrated with new stuff that fails. Makes me want to hold on to old stuff, built, apparently, when we still knew how to make products that work!

Anyway, if any of you guys have an answer or any information whatsoever about any of this, please get back to me, preferably in simple terms. I'm smart in general, but a ignorant about all but some basics about anything mechanical. I always feel so overwhelmed by this stuff.

Also, in case it becomes necessary, if you have any general tips on buying a new AC (or who to go to), please add that as well. I would be SOOO grateful for any information you can give me.

Jeanie

PS... I don't know how to start a new thread so I just replied.

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