DIY Home Improvement, Remodeling & Repair Forum > Appliances > HVAC > Its that time of year, AC not working




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Old 04-30-2009, 07:41 AM  
falconbrother
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My crappy old multi meter was working intermittently. I bought a better one at Harbor Freight and will check out the transformer. Thankfully it is still reasonably cool here in NC. But, soon it's gonna get hot outside.

Again, I really appreciate all the help. I am one of those people who don't mind calling the service guy when I need to but, I really like to be, independent and able to fix my own stuff. I have found , over the years, that with some mechanical ability and a knowledge of tools one can fix a lot of stuff. Having the nerve to jump in their and try and knowing when your over your head and need to stop and call the man is the biggest battle. I usually will push it a little bit and try things that are a bit scary at first. In those cases I try to never do anything I cant reverse if I see that I am really messing things up.



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Old 05-04-2009, 12:42 PM  
falconbrother
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You were right, the Transformer was burned out. I inspected the 24 volt wiring as best I could and replaced the transformer. The unit worked with fan and heat. But, when I switched to AC the outside unit did nothing and the new transformer burned up. Nice!

I have a theory and I think I have to call the pro on this one. Our house was built in 98 and it was equipped with a control so the city could cut out our outside unit during times of peak power usage. They stopped using that system about 18 months ago, or more. But, I think it has shorted out and screwed me.

As far as I can see there is a red and a white 24 volt wire coming from the control board to the outside unit. One of those wires goes to the contactor and the other is routed through the city's contraption. Any, no call is making it to the outside unit. If I close the contactor the outside unit spins up nice. The issue is in the 24 volt system and I feel pretty sure that it is that junk the city insisted be placed on my house.

Can I bypass it by just bypassing it? There is basically two wires that act like a switch I suppose for the contactor control. Do you think I could just close that circuit and let the calls for AC come straight to my outside unit from the Control board.



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Old 05-04-2009, 05:10 PM  
kok328
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Yes, bypass the city's cut out. There should be a brown casing wire that follows the copper refrigerant lines to the compressor outside. The city spliced into one of the two wire inside the brown casing. Just find where the wire enters the city contraption and exits the city contraption, disconnect those two ends and wire nut them together. Now the 24VAC signal will reach the contactor coil and engage the compressor and fan. You might consider either fusing the transformer or purchasing one with a built in breaker, just in case the city comes back and shorts you out again.

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Old 05-06-2009, 09:15 AM  
falconbrother
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Hey, the problem seems to have been a shorted contactor. I have bypassed the cities contraption, they no longer use it anyway. Thanks so much.

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Old 05-06-2009, 10:46 AM  
falconbrother
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I spoke with an HVAC friend of mine and he laid out the typical scenario for a bad transformer. His opinion is that during the spring within the first few hot days lots of people turn on their AC. The power company switches phases and sends a jolt of electricity down the line and capacitors and contactors get damaged. The local HVAC supply says they have sold 1000 capacitors this spring. Anyway, I have a contactor on order and it should be here today or tomorrow. I replaced the transformer but, haven't put any power to the system till the contactor is installed. That will be the moment of truth.

I really appreciate your help. You suggested early on that one of the first things I needed to check was the transformer. I will admit that it wasn't one of the first things I checked. Heck, I didn't even know where it was till I had to really start running down wires. Getting to it looks hard but is very easy.

Have a great day!

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Old 05-06-2009, 11:46 AM  
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Good job! Have a cool summer.

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Old 09-24-2010, 07:10 PM  
RichCPZ
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Default update on your outcome HAVC problem

Hello, I was pleased to find this post as, I am having the same problem and the same air handler unit. I blew two transformers. Lucky they were only 9.88 each. So, there is a short going on some where.
I don't know if it may be the circuit board or not, I even had a HVAC guy out and he installed a new thermostat, power switch, a fuse on the line and his transformer blew also, he said it maybe about 500.00 bucks to replace the board , so I was glad to see you found it for 90 bucks on ebay. Here in Atlanta I have a HVAC store I can visit first to see if they have the board. But, was curious about the outcome of your problem. Did it turn out to be the board or was it the "contactor"
I would love to fix this myself since I'm already about 200 bucks in the hole with the HVAC guy..Whom, I haven't been billed by yet, I just asked him for a price on a new unit and was told 4700.00 bucks "ouch" but, still not back with the 1500.00 tax break. So, I'm in a toss up!

Thanks, for any help



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