Thermostat wired wrong?

[mac0822]

Hello,

I own a 2012 Silverback 35QB4. I was told (after I bought it from a private seller) that the A/C did not work upon delivery to them and it was replaced by the dealer. The A/C works great.

The problem is.....The heat will not come on, UNLESS I trip the A/C breaker. Once I trip the A/C breaker, the heat works perfectly. This becomes annoying on days that I want to use both A/C and heat (common in Vermont). So I assume that the new A/C was wired incorrectly. It's the standard Dometic thermostat.

Does anyone have a suggestion on how I should fix this? Thanks for your help!

[Bama Rambler]

Have you looked at the wire colors in the t-stat?

I happen to have a picture of a t-stat wiring from our old unit.
+7.5 = red
COOL = yel
FUR = wht
Hi FAN = BLU
FAN = BRN
GND = GRN

There's also a service manual here. You can use it to ensure that the 6-pin connector is wired correctly also.

[Crockett]

sounds as if the lower board is losing ground when the 110 in on. polarity on the 110?? run a jumper from the green to a known ground and try that...