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Phil, Mechanical Engineer
Category: HVAC
Satisfied Customers: 8688
Experience:  Retired HVAC/ Electrical & Boiler contractor. Industrial
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why does my furnace come come on at wrong temp

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why does my furnace come come on at wrong temp
Welcome to Just Answer!.
Tell me if this is a new thermostat or an older one that used to work before but is not not working correctly. Tell me please wich color of wires goes to each terminal on the thermostat.

Tell me the model number of the thermostat. We can go from there.

I hold questions open after positive ratings to allow for unlimited follow up. Please be patient though. The research & typing take time

Customer: replied 4 years ago.

hunter #42999 yellow to W, red to rh, another red t RH-RC. before i shut off emergancy swich off. it started,shut off and on a couple of times,then would not shut down. it s 80 degree outside

Hello again.

You have it wired for heating only.

The furnace should shut off when you remove the yellow wire from the W terminal.
The thermostat should be level to operate properly....

If the furnace fails to shut down the gas valve, so that the flames go out, when you disconnect the yellow wire landed on W, so that there are no wires on the W terminal... then it is not a thermostat problem but problems in the furnace.

Tell me if this is a new thermostat, or a old one that had worked earlier.

If you have air conditioning you need at least 4 wires.

Let me know, we can go from there.

Customer: replied 4 years ago.

older everything. i have home insurence. i just bought this iam covered for a year.just wanted to know what caused it to run. its a texaco furnace.40-50 years old. mass save can help pay for new one next year
iam going for heat pump. just have a fans to keep kool. thanks

Hello again, thanks for the information.

Disconnect all of the wires from the W terminal... if the furnace flames stop the problem can be fixed by replacing the thermostat.

If the flames stop but the fan continues, then the thermostat is ok but the furnace fan Control is bad.

If you click the 'good or excellent service' buttons I can keep this question open for you to continue with any further coaching you need, Please do not rate my service with a 'bad or poor service' rating... that hurts badly on my end.

We can go from there with no time limit.

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