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Old 11-11-2008, 11:34 AM   #1
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Rheem furnace blower motor does not come on automaticall


Hello -- I have a Rheem nat/gas furnace circa 1980 (RGAC-080C). The burner ignites but the blower does not come on. The burner then extinguishes when it overheats. The blower WILL come on in MANUAL mode (at the thermostat). I have replaced the fan limit switch and the blower relay. The motor and capacitor are new. Any ideas what to check next?

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Old 11-11-2008, 10:15 PM   #2
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Rheem furnace blower motor does not come on automaticall


is it a combo fan limit or seperate fan and limit if its a combo is it 3 wires or 4 you may have wired it wrong you should be able to rotate the dial and turn the fan on although its reccomended not to do that more info needed

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Old 11-11-2008, 10:51 PM   #3
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Rheem furnace blower motor does not come on automaticall


Four wire. Two wires on top portion for blower, bottom two wires for burner. There was a jumper for low or high voltage and I broke it because the original was broken also (been working for 20 years like that). The fan limit was nearly an exact replacement. It was an 8-inch probe-style and the connections were FOOL proof. Two large upper wires for fan blower motor. Bottom wires for gas valve actuation).
Watching the wheel rotate during burner flare-up, and with AC meter on output of fan limit switch, fan limit switch IS working properly (it is new as I have stated and verified).
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Old 11-12-2008, 12:13 AM   #4
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Rheem furnace blower motor does not come on automaticall


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Originally Posted by wrightti View Post
Four wire. Two wires on top portion for blower, bottom two wires for burner. There was a jumper for low or high voltage and I broke it because the original was broken also (been working for 20 years like that). The fan limit was nearly an exact replacement. It was an 8-inch probe-style and the connections were FOOL proof. Two large upper wires for fan blower motor. Bottom wires for gas valve actuation).
Watching the wheel rotate during burner flare-up, and with AC meter on output of fan limit switch, fan limit switch IS working properly (it is new as I have stated and verified).


so if you jump the fan wires the fan runs? youknow bypass the control if so the controls bad and if its a honeywell control its not unheard of. you can try rapidly switching the auto on switch of the combo limit back and forth but its prolly a bad control seems like back in the day it would prolly be like 1 in 5 or 6 were bad bottom line if you rotate the dial and it dosent click till it gets to the limit setting its bad might be able to remove it and see whats going on with it
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Old 11-12-2008, 04:52 PM   #5
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Rheem furnace blower motor does not come on automaticall


There's 120 volts on the motor 'output' terminal when the heat exchanger reaches 150 degrees.
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Old 11-12-2008, 05:29 PM   #6
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Rheem furnace blower motor does not come on automaticall


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There's 120 volts on the motor 'output' terminal when the heat exchanger reaches 150 degrees.
been along time since ive worked onsomething that old but if memory serves me there is a control box in the blower compartment where fan wires go to and speed adjustments are made open it up and you will probably find the wire going from the fan control to that box is hooked to a wire that isnt being used at the motor

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