DIYbanter - View Single Post - Real post: Rheem heater fan won't shut off, need advice

Joerg

hr(bob) wrote:
On Dec 5, 2:03 pm, "Tim Zeifer" wrote:
I have been having an intermittent Rheem air conditioner/
heater problem. The blower won't shut off unless I cut
the main power. The furnace shuts off fine. Switching
off the fan or anything on the thermostat won't shut it
off. The technician says that they won't repair it unless
they find it dead. By the time the technician arrives the
AC is working again because it usually fails at around
1-4AM then resumes working again at 5AM.

I am now deciding to replace the parts myself but
need some help. I'm not certain but I think the
symptoms point to the blower relay D7 or the fan
cycle control switch F7 on this schematic diagramhttp://www.freewebs.com/acrepairs/RHEEM.jpg.

Where is the fan cycle control switch is located in the
Rheem heater - is it inside the furnace?

Thanks
Tim

Do you mean the fan that circulates the air through the house,
assuming it is a forced hot-air, cold air furnace?

There is a switch that controls when the blower is on, in the heating
cycle, that keeps the blower running until the plenum temperature goes
below a certain level so that as much heat as ppossible is
extractred. If that switch contact is physically sticking, the blower
will run continuously. But you indicate turning the main power switch
off and then back on fixes the problem, so unless there is mechanical
vibration when you cycle the power, there is something else going on.

IIUC some of those fan/limit controls have an internal pre-heater and
then it can happen that the contacts finally let go when that pre-heat
has vanished because the power was cut.

--
Regards, Joerg

http://www.analogconsultants.com/