Help! Nest thermostat for Trane 4TWR4 heat pump system


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Old 11-12-18, 07:54 PM
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Help! Nest thermostat for Trane 4TWR4 heat pump system

I’ve had the Nest thermostat for about 5-6months now. It’s worked great until today. We went out of town and when we got home the temperature dropped into the 30s. The nest read error E106 and said there was a problem with the w2/aux wire. After talking to tech support for the longest time they finally told me to just cap that wire off. Well the heater has been “working” but it’s only blowing air but not heating. I have a 4 month old baby and cannot have a cold house! Please help. I’ve attached pictures of the wiring from my old thermostat and the wiring from the nest before I disconnected the white wire. I also added a picture of the manual for my unit.

**i also tried putting the white wire into W1 but it gave the the same error message**

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Last edited by PJmax; 11-12-18 at 10:01 PM. Reason: reoriented/enlarged stat pics
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Old 11-12-18, 10:07 PM
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Welcome to the forums.

I couldn't see your small pictures. I still can't read what * wire says on the nest display.

You need to have the white wire on W2/AUX. That controls the electric reheats.
Try removing the wire from the * and see if W2/AUX is normal.

On many heat pump systems.... the white and black are connected to the same place inside the air handler. You may need to check in there to see how it's connected.
 
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Old 11-13-18, 01:40 PM
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Yes the white and black are in the same place inside the air handler. Sorry about the small pictures, I don’t know how to control the size, I just uploaded straight from my phone. The * on the nest says dehum. I know in the unit manual it says the black wire is emergency heat. So should I still connect it like you recommended?
 
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Old 11-13-18, 02:16 PM
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Ahhhh..... that's the problem.

Leave it connected as you had it. Go into nest programming and change the * from dehum to E HEAT.
 
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Old 11-13-18, 03:35 PM
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Ok I did that. The error message is gone with the white wire disconnected. It is still blowing cool air though. It’s like it wants to warm up but it’s too cold outside. I tried connecting my old thermostat and it fried the fuse for some reason. I connected it the way it was before the nest. So we replaced the fuse and hooked the nest back up but it’s dtill doing the same thing. Still blowing cool air.
 
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Old 11-13-18, 03:37 PM
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Did you put the white wire back on W2/AUX ?

W2/AUX is back up electric heat.
* is Emergency heat
 
 

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