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

Switch Blue and White wires

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?