Hello!! I have been told this should be a simple replacement. However I have a trane heat pump and it was running off an old mercury thermostat which I was told to replace. We had some one (stupid) (not a professional) replace it and they installed a one stage thermostat for either electric or gas not a heat pump with auxiliary heat. Now my system is old but it works really good with the proper thermostat but now I need to try and figure out which wires go were if any one can assist please reply. I know th basics like
R-red
G-green
O-orange
Thanks in advance for any help,
Michelle

Old thermostat brand and exact model number?
New thermostat brand and exact model number?

The one currently on my wall is a white rodgers 1F80-261 pro-specs #80s3wb single stage. The one I bought to replace it is a Honeywell for a heat pump model rth3100c. The Honeywell has 9 wires location E, AUX, Y, G, O, L, R, B, C. I know th red wire goes to the R, and the yellow wire goes to Y, and the orange wire goes to O, and the green wire goes to G. What I really need to know is were the brown,grey,blue and tan wires go.

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Originally Posted by mimij1990

The one currently on my wall is a white rodgers 1F80-261 pro-specs #80s3wb single stage. The one I bought to replace it is a Honeywell for a heat pump model rth3100c. The Honeywell has 9 wires location E, AUX, Y, G, O, L, R, B, C. I know th red wire goes to the R, and the yellow wire goes to Y, and the orange wire goes to O, and the green wire goes to G. What I really need to know is were the brown,grey,blue and tan wires go.

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Here is a cheat sheet so to speak for the old trane systems. Some of the wires for the trane system you may not use (like outdoor sensor)