[Patrick Murphy]

Greetings:

I have an attic furnace that heats the upper level of my home.
Now that the weather is cold I went to turn the heat unit "on" only to find out that there is nothing on the LCD window on the thermostat.

I have checked the furnace breaker and reset.
I have checked the breaker outside at the outdoor fan units
I have taken the lower level (known good) thermostat off the wall and installed it in the upstairs position with the same result. Nothing on the LCD on the Honeywell thermostat.
I have checked the fuse at the upstairs unit and its good, no burn or ark marks.
I have checked the wire connections in the furnace for the thermostat wire, and everything looks tight.
Checked all the connections at the wall plate where the Honeywell thermostat snaps on and every wire is tight.
I have not checked any voltages at the wall mount as I am not sure which wire(s) to check to one-another. i.e. "G" to "Y" etc.

Something is not allowing power to get to the wall mounted thermostat?

[hvac1000]

You need to check and see if the low voltage 24 volt transformer is working in the up stairs unit. The transformer could be defective. The 24 volt transformer supplies the voltage for the control circuit and the transformer has to be working for the thermostat to work along with the rest of the devices. The transformer is located in the unit upstairs.

[Patrick Murphy]

I found a 5 amp fuse blown, I will replace that first and see if that works, if that blows I guess I have a transformer isssue.

Thank you for your kind help

[hvac1000]

Yepa fuse will do it. But you could have blown the fuse messing with the thermostats. If the fuse blows again then you will have to find the ofending part or short circuit in the low voltage wiring.

[Patrick Murphy]

Love the "Yepa"
Replace the fuse and the panel is now operational... that's the good news!

Bad news is the furnace is not firing up!

Have to run for the night and will be back!

One last question for the night... Does Lowe's sell the transformers or will I have to procure from a Heating and Air Company?

Thank you again for all your help!

[hvac1000]

I think Lowe's sells transformers but be sure to get at least a 40VA size if you can. Also make sure you know the voltage that the unit runs on. Gas is usually 110/120 volts and electric furnaces use 220 volts. Yours is probably gas since you called it a furnace..