I have a rooftop electric heater (cumberland). It has a heat strip in
along with the A/c unit. My A/C works fine but the heater fan doesn't
run when I turn from A/C to heat and bring the set temp up above the
actual house temp. When I move the fan switch from Auto to ON the fan
runs but doesn't work off the thermostat. I have a meter and went up to
see what was up but everything had 220 volts where it seemed it should
and then i took off a panel and the inlet to the fan (the one that
delivers the air to the house, not the little a/c fan above the
condensor)had a ton of warm/hot air coming out of it. My question is
what if any temp sensor or contactor(?) tells the fan to turn on since
the thermostat is obviously working due to the heat strip being on? Any
and all help is way appreciated. BTW I checked all the fuses and
breakers on unit. Also there was a loud clicking sound happening every
few minutes up there, I figure that must be a overtemp switch of some
sort to not let the heat strip get so hot as to cause a fire. I have
somewhat of an electric background and am comfortable checking and
doing simple replacement type stuff (Read: I shut down the power when
ever I'm going to actually change something) Thanks guys!!

Either the thermostat is the wrong one (it may need to power the "G"
wire on a call for heat), or it has a bad heat sequencer. On some
units the heat sequencer brings the indoor blower on with the first
strip heat element. The schematic diagram in the unit should show which
problem you have.

Stretch

wrote:

I have a rooftop electric heater (cumberland). It has a heat strip in
along with the A/c unit. My A/C works fine but the heater fan doesn't
run when I turn from A/C to heat and bring the set temp up above the
actual house temp. When I move the fan switch from Auto to ON the fan
runs but doesn't work off the thermostat. I have a meter and went up to
see what was up but everything had 220 volts where it seemed it should
and then i took off a panel and the inlet to the fan (the one that
delivers the air to the house, not the little a/c fan above the
condensor)had a ton of warm/hot air coming out of it. My question is
what if any temp sensor or contactor(?) tells the fan to turn on since
the thermostat is obviously working due to the heat strip being on? Any
and all help is way appreciated. BTW I checked all the fuses and
breakers on unit. Also there was a loud clicking sound happening every
few minutes up there, I figure that must be a overtemp switch of some
sort to not let the heat strip get so hot as to cause a fire. I have
somewhat of an electric background and am comfortable checking and
doing simple replacement type stuff (Read: I shut down the power when
ever I'm going to actually change something) Thanks guys!!

We can't see it from here. Stretch covered the two most likely causes,
though some stats can be configured to run the blower on a call for
heat, so you don't necessarily have the wrong stat per se. But it is
most likely that you either have a sequencer out, or a wire burned off.
It is also possible that it is miswired. Time to call a local tech.

hvacrmedic