I'm trying to replace my Honeywell T87F thermostat with a Honeywell RTH7500D. Have tried all combos and can't seem to get it to work. Here's the 4-wire connections to the T87F:
Blue Wire --> Y terminal
White Wire --> W terminal
Red Wire --> R terminal
Green Wire --> G terminal

Thanks in advance

Why will it not work? Did you do a installer setup? Does your new stat require 24 volts to run? Or will it run off battries?? Did you put a jumper from rh to rc??

The symptoms are
For A/C - fan comes on but condenser does not
For heat - heater fires up but fan does not come on
I do have the rh to rc jumper

The new stat can run on batteries and I didn't see anything in the instructions about an installer set up

Thanks

Select Fan only, what happens?

Fan only works fine

Switch Blue and White wires

Quote:

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Originally Posted by KeepItSimpleStupid

Switch Blue and White wires

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If the white and the blue were backward the heat would not come on in the heating cycle would it??

This is turning out to be a very odd problem for such a easy job

True. Have to put thinking cap on.

I am going back to installer setup problem. Sense he did not do one it may be running on heatpump, or electric furnace. You do have the b on y? Not y1 or y2? What is throwing me off is why the fan will not come on in heat mode

Could no AC, be because the breaker/fuse is tripped for the AC. Can happen if the Heat breaker was not turned off when changing the stat?