Rheem fan runs all the time


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Old 02-22-10, 05:27 PM
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Rheem fan runs all the time

I have rheem gas furnace that worked fine last night and noticed today that the fan was blowing cold air. Turned the thermostat all the way down but the fan keeps running. Fan is still blowing but there is no heat coming out.
 
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Old 02-22-10, 06:29 PM
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Look on the thermostat and make sure that the little switch that
is labeled FAN is in the AUTO position and not the ON position. If that part is okay then do the following.

Open the blower compartment on the furnace (turn off the power first) and look for the thermostat wiring. There should be a green wire as part of the thermostat cable. Disconnect this green wire and tape the end. Replace the compartment door and see if the blower now runs properly. If it does operate properly the problem is in the thermostat OR the wiring between the thermostat and the furnace. To check the wiring do the following.

Turn off the furnace power again, open the blower compartment and replace the green wire. Close the compartment but DO NOT turn the power on yet. Go to the thermostat and remove the green wire from its terminal. Tape it up and then turn the furnace power on and see if it operates normally. If it does NOT operate normally the thermostat cable is damaged but if it DOES operate normally the thermostat is defective.

If removing the green wire from the terminal in the blower compartment had no effect the control board at the furnace has a defect.
 
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Old 02-22-10, 06:56 PM
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It is a simple thermostat it does not have anything other than a temperature gauge. There is no fan switch on this thermostat.
 
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Old 02-22-10, 09:48 PM
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Is this a Very old furnace with a fan limit?



If you have this fan limit, try poking that round disc under the cover to see if it is hung up.

It could also be a tripped high limit.
Do you change the filter often?
 
 

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