Sparks in the Thermostat

Old 10-13-04, 01:00 PM
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Sparks in the Thermostat

I tried to turn my furnace on this season and when I turned the thermostat to activate the furnace there were sparks coming from the unit. I have a honeywell thermostat and thought that it was fried so I went out to purchase another one. I installed it and the same thing happened. I checked all the wires and nothing seems to be crossed so I am not sure where to go next. I have a Williamson "Temp-O-Matic" furnace and it is probably about 12-15 years old. The pilot light wont come on and I have tested the circuit breaker and it seems to be receiving energy. Is there any others wires I should check or any other interventions I should be lookng at?
If anyone can help direct me on the right path I would really appreciate it.
Cold in Buffalo
Old 10-15-04, 01:51 PM
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Hello grovergolf. Welcome to the Heating Furnaces forum topic and the Do It Yourself Web Site.

Tiny sparks are normal. The voltage to the thermostat is about 24-36 volts. Tiny spark will result if wires touched together without T-Stat in place.

Sparks which are that intense to burnout a T-Stat indicates there is another problem unknown to either of us. Betwen last season and now, something must have changed to cause sparks enough to burn out a T-Stat.

About the only test you might be able to run is to check the voltage on the low out put side of the transformer which should be on the heating unit. One side will have the heavy house voltage current while the other side or on top will be the thin wires which go to the T-Stat and safety devices on the heating furnace.

The low voltage should be about 24 to 36 volts and not more than that or there abouts. Use a volt meter or volt ohm meter to do the testing. Not liekly the transformer is allowing more current than that or full house current to pass by into low voltage electrical system on the heating unit.

Check back on your question several more times. Heating professionals and other members posting replies in this forum topic may offer you additional advice, ideas and or repair methods.

Use the reply button to add additional information or questions. Using this method moves the topic back up to the top of the list of current questions automatically.

Regards & Good Luck. Sharp Advice.
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