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Posted by RBM on April 15, 2007, 5:20 pm
I don't know anything about this type of furnace, but I'd like to take a
stab at what it may be. I would think it normal for the heating elements to
come on without the blower. I would think there would be a sensor in the
heating chamber that turns on the fan at a set temperature, and off at
another set temperature. I would believe this or another sensor would also
turn off the elements if the blower didn't come on and the heating chamber
reached a set high limit. Because this is an electric furnace, this sensor
would have to be acting through a contactor for at least the heat part,
possibly the blower as well. If there is something wrong with this sensor,
it may be causing the safety control to go into a lockout mode
> I'm having an intermittent problem with my 7 year old Rheem electric
> (forced air) furnace. About 2-3 random times a week the furnace will
> fail to turn on despite the room temperature being below the
> thermostat set value. To get it to function normally, I turn the
> furnace off (at the thermostat), wait a few seconds, and turn it back
> on. The furnace will then return to normal function from anywhere
> from 12 to 72 hours, then it'll happen again.
>
> Other interesting notes. When the furnace is 'malfunctioning' I have
> seen the heating coils on, but not the fan (this obviously should
> never happen). My immediate thought was that the blower motor was
> going bad. The problem with this theory is that the blower always
> comes on when I turn the fan on at the thermostat. So it appears to
> me that the thermostat is either not sending the command to turn the
> blower on (but is telling it to turn the heating elements) or that the
> furnace is unable to always get the motor going. The thermostat is
> digital (White-Rodgers) so it seems unlikely that it would work
> intermittently.
>
> Oh and I did replace the motor start capacitor because it was cheap
> and easy. It didn't help.
>
> I am stumped. Anyone have a clue here?
>
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