# possible blown transformer, wiring problem?



## HvacWiz (Nov 24, 2006)

*You probaly have a short in the low voltage side of system... thermostat, limit switch or gas valve, install a low voltage fuse(3amp or 5amp) inline with transformer common wire. then power up furnace, if fuse blows then you know you have a short. Then proceed to disconect wires from t-stat on circuit board and try again if fuse still blows then remove wires from gas valve and try and on down the line......*


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## biggles (Jan 1, 2008)

remove both sides of the TR in place and ring out (ohms setting) the wire pairs out each side 120V and 24V side if you don't get continuity on either it is shot...local grainger supply has then cheap and get on with a CB on the 24 side...your right on the 24V colors yellow is R... blue is C.sounds like it nuked out...on the low side.taping the un used primary wires is just for saftey but the common white is the only connection there between the 3 voltages...taps but a good practice but wasn't the cause if you have a control board within the furnace and the TR cooked be aware it shorted from there from the mis wire...


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## rtockstein (Jan 13, 2012)

thanks for the advice from both! This should definitely help.


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## jasonreck71 (Jan 14, 2012)

rtockstein said:


> thanks for the advice from both! This should definitely help.


I would guess it is fried, just went through the same thing on my heat pump...After it smoked it never worked again. I found the short in my heat pump outside. the 2 compressor wires were zip tied to a cooper tube and after 2 years they wore through to the wire

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## rtockstein (Jan 13, 2012)

I used my meter and I've got continuity from the 120 hot to the 120 nuetral, and the 24 hot to the 24 neutral. I also wired it up correctly and measured 27V from the 24hot to the 24 neutral. So it's not fried, right?

Which is amazing, since I heard some crinkling and saw a tiny bit of smoke.


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## harleyrider (Feb 20, 2007)

transformers and electrical motors all run on smoke.....but when the smoke gets out they are fried.


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