[QuietlyCrazy]

First the sticky at the beginning of this topic on wiring codes is wrong; brown (tan) is not normally common, it is almost always a Trane-specific wire not used on non-Trane/Weathertron/GE stats. Common is usually blue or black and connects to C. It also doesn't answer my issue, which I've never seen.

Next, my problems is my old stat (Weathertron 3AAT80B1A1) has some odd connections. My system is a Trane XL1200 (TWX736A100A) heat pump. A manual on the Trane would help, but can't find one.

The biggest issue is F is connected to the White wire (F would normally be second fan, but white is normally 24VDC). In short, white connected to F is bizarre (to me)

Normally F is left unused. I don't have a manual for the Weathertron either, but here are the existing connections and my best guess for what they are...

F = White??
W is jumpered to X2
X2 = (black wire)
U not used (but tiny mfr wire links to the W and X2 bundle).
B = Blue (likely Common on Trane)
Y = Yellow (compressor relay)
G = Green (fan)
O = Orange (changeover)
R = Red (power)
T = Tan/brown (Trane-specific; not typically used on newer).

My new stat White-Rodgers 1F97-1271 is pretty straight-forward if it weren't for the weird F connection on my old stat confusing me on what to do with White and Black:

Here's what I'm pretty sure of and confused with on the W-R stat:

Blue = C (24V common)
Orange = O (changeover valve energized cooling)
Yellow = Y (compressor relay)
?? = W (heat relay) NOTE: this would normally be white, but the old stat confuses!
Brown/tan - tape off - only used on Tranes
Red = RH/RH jumpered (power)
?? = L (malfunction light) (ignore? )
?? = B (changeover valve energized heating) (I think is unnecessary because of O)
Green = G (fan relay)

Also the White-Rodgers suggests for heat pump I jumper W and Y, but I've also heard this is unnecessary. Anyone know for sure?

So, I've got a black and white wire left and don't know where they go based on the weird F/white connection on the old stat.

Anyone? Much thanks in advance!!

[hvac1000]

((It would be beneficial to all to keep your posts together as one thread so all can read and follow.)0

Follow the wire you are concerned with and find out where it lands in the equipment. This will give us a idea of what it is used for and where it should be landed. I have no diagrams for your old thermostat. Sorry