New thermostat worked fine then burning smell and no AC

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Old 02-05-14, 08:03 PM
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New thermostat worked fine then burning smell and no AC

I recently installed a new thermostat on my 24VAC heat pump system. The AC was working fine for a few days then today I noticed a burning smell throughout my house. The system is now blowing hot air only and blows hot air in AC mode as well. What could cause this?
 
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Old 02-05-14, 08:12 PM
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How was the old stat wired?
What was the make and model of the old stat?

How is the new stat wired
What is the make and model of the new stat?

What is the make and model of your air handler?

Was the heat pump working in cool mode? Did this problem start when placed in heat mode?
 
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Old 02-05-14, 08:30 PM
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When connecting the wires I had 1 left over.. the W2 wire. I never tried to turn the heat on. The new thermostat is a Honeywell the old one is a SimpleComfort.

The air handler is a Lennox.

Yes, the cool mode was working for about 4 days.

Thank you!!
 
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Old 02-05-14, 08:56 PM
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Honeywell has made many thermostat models through the years, possibly hundreds of models.

Do you have any model numbers?

A common mistake that people make when replacing their heat pump stat is buying a stat this isn't compatible with multistage heat pumps. This is probably your case as well but I cannot check without a model number of your new stat.

If you feel that you can provide the wire = color combination at the new stat and the wire = color combination at the air handler, and the model number of the new stat we may be able to help you resolve this problem.

If you had the wire = color combination of the old stat as well as the model number of it we would not need to open up the air handler.
 
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Old 02-05-14, 09:01 PM
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Sorry the Honeywell is RTH6500wf and the original Simple Comfort is: 3201

I have pics of the original wiring and will take a pic of the new wiring now.. will post in a couple.. thank you again!
 
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Old 02-05-14, 09:08 PM
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OK here we go.. Again thank so much for your help!!

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Old 02-05-14, 09:17 PM
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https://customer.honeywell.com/resou.../69-2718ES.pdf

Did you configure the stat to match your system?
1 = 5
2 = 0
 
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Old 02-05-14, 09:22 PM
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Yep, I did all that too. Like I say.. it was working great for about 4 days then tonight I could smell a burning odor then next time I tried to kick the AC on it was blowing warm.
 
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Old 02-05-14, 09:26 PM
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I see blue connected to common on the new stat. I do not see this on the old stat.

Is the outdoor unit running with a heating and cooling demand present?

The O wire supplies 24 volts to the reversing valve outside to put it in cool mode.
If the outdoor unit runs, I'd check that wire connection first.
 
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Old 02-05-14, 09:38 PM
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You can see the C wire in this picture the wire is connected to "C" on the old Thermostat

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How can I check the O wire other than insuring its plugged in? I see that it is indeed firmly screwed down.
 
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Old 02-05-14, 09:56 PM
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Does the fan turn off and on from your thermostat?
 
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Old 02-05-14, 10:05 PM
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Yes, it does function still.
 
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Old 02-05-14, 10:11 PM
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Does the outdoor unit turn off and on from your stat?

Do you have a volt meter?
Are you getting 24 volts between C and O outside?
 
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Old 02-05-14, 10:15 PM
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Yes, the outside unit does turn on and off but no I don't have a volt meter
 
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Old 02-06-14, 12:53 PM
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Anyone else have any input?
 
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Old 02-06-14, 04:48 PM
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The burning odor is alarming. I'd open the indoor unit panel and inspect for burned wires.

Do you see any bent pins behind the stat? (especially the pin connecting the removable portion of the stat to your O terminal)

If all appears fine, you can try tempoarily moving the orange wire from O/B to RC (leaving the jumper installed and Red on Rh) to see if you get cooling.
 
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Old 02-07-14, 03:47 PM
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Update: last night the AC starting to work on its own again with no problems.. what in the world could cause this? Faulty Thermostat?
 
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Old 02-07-14, 04:54 PM
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This is very possible.
The thermostat may still be under warranty.
 
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