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  #1  
Old 08-12-2012, 07:30 PM
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Home HVAC question

My home a/c system started acting out today. Last night I noticed that it was not working so I fiddled with the switches and got it running yesterday but today I noticed that the house was warming up. I went outside and I could see the blower fan running but the compressor was not working. I could also hear a relay click on and off. Every now and then it would cycle on but more often not.

A/C guy replaced the contactor and the capacitor but it did dot help. He thought it may have been a bad thermostat but sadly, replacing it did not help.

Any other thoughts?

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Old 08-12-2012, 08:35 PM
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is the condensor fan running? the a/c guy "thinks" is something i never like to hear when paying someone. if you push the contactor does everything come to life?
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Old 08-12-2012, 09:08 PM
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Yeah, it's running, but as the relay is clicking, it's killing the fan. He thought it was the thermostat because he crossed some wires together at the thermostat and the condenser ran well for several minutes while we stood around.
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Old 08-12-2012, 09:14 PM
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Fan running but no compressor: did he check Freon pressure? It could be cutting out due to low pressure.
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Old 08-12-2012, 09:56 PM
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I checked the high side which was at 275 in 108 degree weather. Maybe a little but not too high.
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Old 08-12-2012, 10:07 PM
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Old 08-13-2012, 08:54 AM
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Get another "A/C guy". This should not be guesswork at your expense.
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Old 08-13-2012, 11:44 AM
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Quote:
Originally Posted by alabbasi View Post
I could see the blower fan running but the compressor was not working. I could also hear a relay click on and off. Every now and then it would cycle on but more often not.
Without a wiring diagram, there is no way of knowing what was clicking. Some units start the condenser fan and compressor with the same relay, others use separate relays. If this was indeed the compressor relay, and it ran sometimes there may be a wiring connection problem, a bad contact in the relay, etc. but without testing how would anyone know?

Quote:
A/C guy replaced the contactor and the capacitor but it did not help.
Replacing both at the same time introduces too many variables and prevents you from determining if either or both are defective, but it does run up the bill. You said the compressor ran sometimes, so the contactor and the capacitor may have been OK. How did he determine that these needed to be replaced?

Quote:
He thought it may have been a bad thermostat but sadly, replacing it did not help.
Dude! The condenser fan was running, so it is quite obvious that the thermostat was calling for cooling like it should. The thermostat only signals the unit to RUN or STOP. Why on earth would any "A/C" guy suspect the thermostat?

At this point I would suggest having a serious talk with the "A/C" guy. Ask him how he plans to proceed, and if he is going to keep "throwing parts at it" without any real diagnostic testing, then replace him with a real technician!
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Old 08-13-2012, 11:45 AM
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Quote:
Originally Posted by Jim H View Post
Without a wiring diagram, there is no way of knowing what was clicking. Some units start the condenser fan and compressor with the same relay, others use separate relays. If this was indeed the compressor relay, and it ran sometimes there may be a wiring connection problem, a bad contact in the relay, etc. but without testing how would anyone know?
Agreed.

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Originally Posted by Jim H View Post
Replacing both at the same time introduces too many variables and prevents you from determining if either or both are defective, but it does run up the bill. You said the compressor ran sometimes, so the contactor and the capacitor may have been OK. How did he determine that these needed to be replaced?
He replaced the condenser first and then the contactor. He did a visual inspection of the contactor and showed me where he saw arcing on the contacts which is why replaced it. I'm assuming that this is what was clicking. To be fair, when he turned up, the system was behaving quite well.

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Originally Posted by Jim H View Post
Dude! The condenser fan was running, so it is quite obvious that the thermostat was calling for cooling like it should. The thermostat only signals the unit to RUN or STOP. Why on earth would any "A/C" guy suspect the thermostat?
He pulled the thermostat off and jumped the wires, then we sat around for about 10 minutes and the system behaved just fine so he determined it was the problem. After he left I bought a new thermostat and wired it up. Again, fine for 10 mins before acting out.

Last night, I bridged the connections behind the thermostat, as he did and could still hear the clicking so it was clearly not the thermostat.

Quote:
Originally Posted by Jim H View Post
At this point I would suggest having a serious talk with the "A/C" guy. Ask him how he plans to proceed, and if he is going to keep "throwing parts at it" without any real diagnostic testing, then replace him with a real technician!
It turned out to the transformer in the attic. Even though it got hellish hot last night, I really can't complain. He charged me $190 all together, including 2 call outs (one on a Sunday), a conductor, capacitor and the transformer.

I really can't fault his diagnostic skills, this system is pretty old and I liken it to working on old cars. Sometimes you just need to look at how old things are and replace them using a process of elimination. In the end, I don't think he over charged me.
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Last edited by alabbasi; 08-13-2012 at 11:46 PM.
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  #10  
Old 08-13-2012, 12:29 PM
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Transformers rarely fail, and attics in Dallas are toasty this time of year. If it had been cooler, he might have been more thorough in testing/diagnosis. But, A/C systems don't usually fail in the winter! I can't say that I'd blame him for missing that either. Hey, at least you didn't have to buy a compressor.

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