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A/C Help


Sully

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My turn I guess... :(

 

I have an all electric house with an air handler and heat pump. Both units are only 4 years old. I have a Honeywell digital thermostat that is 4 years old as well. The entire system worked fine all winter. 2 weeks ago, when it was a bit warmer, the A/C was working fine as well. I was off work all last week and kept the A/C off the entire time. And of course since I'm back at work this week, the wife and kid "are going to be too hot this week and want the A/C on". :wtf:

 

Anyway, I go to turn it on last night and get nothing. The thermostat display works. It says "Cool" and when I switched it on it gave me the "Wait" indicator. I hear it click like it's working, but nothing happens. I flipped all of the Handler & Heat Pump breakers. Nothing.

 

I pulled the thermostat off the wall and noticed one of the AAA batteries was expanded and leaked at the bottom end. The contacts had some corrosion on them, but it wasn't terrible. I pulled the batteries and scraped the contacts off. I put new batteries in it and the system continues to do nothing.

 

I've been doing some reading and my wife spoke to a friend whose husband does HVAC for a living. He said that 99% of the time it's not the thermostat. He said it's most likely a failed board, capacitor, or something of the like. I kind of feel like it may be the thermostat due to that battery leaking. I know we have some HVAC pro's on here, so I'm looking for some input on what to check before I drop a ton of coin on a service call.

 

The first thing I'm going to try tonight is replacing the thermostat. If that doesn't fix it, I'll return it.

 

Thanks!

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Do you know where the board is? Is it easily accessible? Have one person stand at the thermostat and cycle the AC on/off while you're standing right infront of the board. Listen for the Relay(s) to click on and off. Also listen for relays on the thermostat itself to click on/off (just re-read, sounds like the thermo relays are clicking on/off).

 

Thats a start, im sure someone with more experience will chime in.

 

PS - Don't get electrocuted.

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The first thing I'm going to try tonight is replacing the thermostat. If that doesn't fix it, I'll return it.

 

Have you ever replaced a thermostat on a unit that has a heat pump? It can be somewhat confusing.

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You need to figure out which two wires behind the thermostat turn on the A/C and tie them together. If the A/C comes on you'll know its the thermostat. Otherwise the capacitor in the outside unit is a very likely thing. Sorry I don't know what wires are what, I have never worked as an HVAC tech, hopefully there is some type of labeling.
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Do you know where the board is? Is it easily accessible? Have one person stand at the thermostat and cycle the AC on/off while you're standing right infront of the board. Listen for the Relay(s) to click on and off. Also listen for relays on the thermostat itself to click on/off (just re-read, sounds like the thermo relays are clicking on/off).

 

Thats a start, im sure someone with more experience will chime in.

 

PS - Don't get electrocuted.

 

Would this be the board on the handler or the board on the heat pump?

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You need to figure out which two wires behind the thermostat turn on the A/C and tie them together. If the A/C comes on you'll know its the thermostat. Otherwise the capacitor in the outside unit is a very likely thing. Sorry I don't know what wires are what, I have never worked as an HVAC tech, hopefully there is some type of labeling.

 

 

Good idea. The wires are labeled and I'm sure I can find something online about the wiring to test this.

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Good idea. The wires are labeled and I'm sure I can find something online about the wiring to test this.

 

Theres some universally accepted color-coding system for HVAC wiring. IE red crossed with green will always turn the fan on, etc. You can find it online.

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Theres some universally accepted color-coding system for HVAC wiring. IE red crossed with green will always turn the fan on, etc. You can find it online.

 

Unfortunately, installers don't always use the right colors for he right functions as most times there are excess wires. I'd go by the actual terminal (IE: R/C/Y/G) first vs color.

 

http://i.imgur.com/1Uz6joK.jpg

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The wires you are looking for are red and yellow (generally). Yellow runs the compressor, the problem is that a heat pump could operate in cooling or heating without energizing the reversing valve depending on the brand. Regardless you can jump them and test the outside unit. Just use a pair of needlenose pliers. Does the air handler blower come on? If the blower Doesn't come on then you likely have an issue at the air handler or the thermostat. 1 out of 500 or so calls is usually thermostat related with this type of thing but it can happen.
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CAREFULLY check for 24v on the low-voltage side of the transformer (i'd throw the breakers, disconnect the low-voltage side, attact a Volt Meter, then throw the breakers back on).

 

Transformer should be right near the inside control board.

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Im betting pops a fuse again this week......Anyone wanna take me up on that?

 

This man taught me everything I know.

 

TEST HIM, DO IT! :gabe:

 

- Thanks again Kyle...3 Summers now and A/C is running Ice Cold/without issue.

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