Hey, I've got a Goodman GMT115 gas furnace that, if turned on, will
not stop heating the house. This started two nights ago, and it may be
a fault in the fan/blower relay switch or something. I've tried
turning off the thermostat, but the only way to regulate it now is to
turn off power to the furnace. The manufacturer website doesn't give
any help. Matching up the manual's wiring diagram with the furnace
control panel and wiring doesn't quite mesh. Any help in diagnosing
the problem, or identifying where the fan/blower relay is?
Somewhere on the furnace you should find a terminal strip where the wires
from your thermostat connect. Temporarily disconnect the red wire and see if
the furnace then shuts. The burner, if ignited, should quit immediately, and
the blower may take a while to turn off since it is most likely on a delayed
relay / switch. The key thing is to isolate the problem to either the
thermostat versus the furnace, which this simple test will achieve.
If the thermostat is stuck in the continuous on condition, then removing the
red wire will reveal that the thermostat and not the furnace is at fault.
If, on the other hand, the furnace continues to run despite the red wire
being disconnected, then the furnace itself is the problem.
There should be a wiring diagram someplace inside the furnace or in the
owner's manual if you want to try to troubleshoot the furnace with our help.
If not, call a competent repair person.
If it continues to heat the house (burners on)
after the thermostat is satisfied,
then it's not a fan/blower relay problem.
If you're confident working on the wiring,
disconnect the thermostat wires (Red and White)
at the furnace. If the gas burners now shut off,
the thermostat is at fault or the wiring to the
stat is shorted. (Shut the power off before working...)
If you're not confident or lack the experience,
wait for the tech.
Brilliant, men! I had read some about the red and white wires, but
your discussion was a little clearer in guidance. I tracked down the
red wire, disconnected it and tried the furnace. It didn't start, so
I reconnected the red and voila, it seemed to "reboot" things and it
is now cycling regularly and maintaining a consistent temp.
That doesn't sound like your problem is solved. I have a feeling that the
problem will reoccur, and possibly has to do with the type of thermostat
you're using. It may have a current robbing, charging system that's pulling
to much current for the relay it's controlling, causing it to stick in the
closed position. Do post back if it happens again
Good foresight on the problem not truly being solved. I had a
feeling, but was hoping for dumb luck. There are two thermostat
controls (Honeywell T8112) in the house. Does it sound like I need a
new blower relay switch?
HomeOwnersHub.com is a website for homeowners and building and maintenance pros. It is not affiliated with any of the manufacturers or service providers discussed here.
All logos and trade names are the property of their respective owners.