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Swenny

themostat power dead

4 posts in this topic

My furnace and air went dead. 

Started troubleshooting by checking voltages at the thermostat, none.  My transformer produces 17 volts but it's not getting to the thermostat.  I trace the wire from the 24v transformer out to what I think leads to the outside compressor unit.  There I find the 220 volt box and a 110 volt romex line into the compressor but I see no 24guage thermostat wire there.  The 220 fuse all check out.

So what happened to my 24 volt therm voltage.  I believe it's suppose to route from the 24v trans to the air compressor unit? then back up to the thermostat.

This is a 20year old GE furnace and air unit. Probably due to be replaced but I can't afford it just yet so I'm trying to milk a few more years from this equipment.  I replaced the fan limit switch last year.

Any help would be appreciated.

Swenny

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Need appliance parts? Call 877-803-7957 now!

To make it easier to explain tell me what color wires you have at the thermostat and what terminals are they connected to. Such as terminal 'r' is red, 'w' is white, 'g' is green, and 'y' is yellow (these would be typical) - I am guessing the romex line is not 110v because there is no need to run 220v and 110v to the condenser (outside unit)

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thanks for the reply.  I have a honeywell ct87b therm unit.  Wires are connected as follows.

Red---Rh

green--G

Blue--Y

White--W

 

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Problem solved.  It was the 24v transformer, primary side was open. replaced with generic type and now all ok.

I was confused at first because I mistakenly thought another 24v transformer in the furnace room was the culprit. It ran to the door bell, not the thermostat.  The problem one was located inside the furnace and hard to get at.  Once I traced the wires it became clear.

I could have figured this out sooner but I have no schematic of my unit.

Thanks for your help.

 

Swenny

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