thermostat question


Old 03-15-04, 06:16 AM
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thermostat question

I have electric forced heat.My heat will not turn off at the control.Does the thermostat need to be replaced?
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Old 03-15-04, 06:51 AM
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Have you tried to turn off the switch on the T-stat?

If it keeps running with the switch on "Off" then turn off power and remove the T-stat from the wall. make sure you make NOTES on what wire goes where.

Make sure none of the wires touch, and turn on the power again.. If the units keeps running, then you may have a relay on the furnace stuck.

Another test you can do before you take out the relay is undo the t-stat wire on the control board (again take NOTES) on the furnace and see if it keeps running.. If the system stops when you remove that set, you may have a t-stat wire that been shorted out.
Old 03-15-04, 07:03 AM
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Are you sure the heat is on or is it just the blower that is on. This is just electric heat not a heat pump? Dont go out and buy a tstat yet. Is the cover on right on the tstat. Hit the side of the furnace hard with your hand and see if it stops. If not like jay said pull the R wire off the tstat and see if it shuts off. ED
Old 03-16-04, 04:53 PM
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My Two Cents

Hello: dgffp

Ed is correct. Trick I used often while in the industry as a service tech. A good smack on the unit will jar the contacts open on the fan relay or fan switch and the blower will shut off.

If that does happen, the relay or fan switch needs to be replaced. Use caution. The power to the unit must be off first before attempting to remove and or replace any part for safety.

The fan relay or fan switch will be located at the end of the fan motors wires on the opposite end of the motor. Ususally in a cover box with electrical wires entering and leaving it.

Jay is correct too. Make a wiring diagram before removal of any wires. They all must be reinstalled exactly as currently found.

If the heat does not shut off, run the tests mentioned by both Jay and Ed. T-Stat may or may not be the problem. Shorted wires are possible but not as likely.

If the unit is a heat pump, advise. We can move the question into the heat pump forum so the heat pump pros can help further.
Old 03-16-04, 05:23 PM
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Most likely you have a stuck sequencer (fancy name for a relay) that controls the heat. It's probably the most common problem to occur with electric heat. You would have to prove this first though before you go replacing it. If you feel comfortable doing so, turn the power off to the air handler, remove the front cover, and make a good visual on the components inside. Then a voltmeter is necessary to further diagnose the problem. THATS always the first thing to do. If your not comfortable with this, call a professional.
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