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View Full Version : Installed Honeywell RTH7400 Thermostat but get no power


gsu90
Jan 2, 2007, 02:49 PM
I have tried to comb through the threads to find a problem that fits mine, but I didn't find it. So please forgive me if this is a repeat question for something that has already been presented.

I have just installed 2 Honeywell programmable thermostats (RTH7000 series). The one for my downstairs unit works just fine, however I can't seem to get any power from the unit upstairs and I have installed them both the same way.

I have 5 wires. Red, Green, White, Yellow and Blue (for C). I have read to check the circuit breaker, but the switch is on. I have also read about fuses, but I have no clue where the box is if one even exists.

I have a outside AC unit and a Goodman indoor gas furnace that is about 12 years old.

Any idea how I should proceed to fix this? Keep in mind I am slow. :)

Thanks

gsu90
Jan 3, 2007, 11:47 AM
I have tried to comb through the threads to find a problem that fits mine, but I didn't find it. So please forgive me if this is a repeat question for something that has already been presented.

I have just installed 2 Honeywell programmable thermostats (RTH7000 series). The one for my downstairs unit works just fine, however I can't seem to get any power from the unit upstairs and i have installed them both the same way.

I have 5 wires. Red, Green, White, Yellow and Blue (for C). I have read to check the circuit breaker, but the switch is on. I have also read about fuses, but I have no clue where the box is if one even exists.

I have a outside AC unit and a Goodman indoor gas furnace that is about 12 years old.

Any idea how I should proceed to fix this? Keep in mind I am slow. :)

Thanks

Can anyone help me with this?

labman
Jan 3, 2007, 09:45 PM
You should have a 24 volt transformer in the furnace. 2 wires from it should go to the control board. One of them may have an inline fuse in it, or there may be a small automotive blade fuse on the board. Does the furnace have an LED on the control board? If you have a volt meter, you can check the R and C terminals at both the furnace and thermostat.