Goodman blower changing speed
#1
06-12-19, 02:03 PM
Goodman blower changing speed
Just installed 2 new Goodman HVAC systems. Running the upstairs AC, the blower intermittently changes speeds from high to medium at random times. Its not a dual speed compressor so it shouldn't be changing.
Downstairs unit works fine. Both units are cooling fine but sounds like a bad relay on the upstairs unit.
Any ideas what could be causing the blower speed changes?
Thx in advance!
Goodman GMH80803BNBD
Downstairs unit works fine. Both units are cooling fine but sounds like a bad relay on the upstairs unit.
Any ideas what could be causing the blower speed changes?
Thx in advance!
Goodman GMH80803BNBD
#2
06-12-19, 06:00 PM
Group Moderator
Welcome to the forums.
Bad relay ? What makes you think that ?
The integrated furnace board controls the blower speeds.
The blower should only work in two speeds if the optional relay was installed.
Try running the blower on FAN ONLY and see if it has the same problem.
Goodman GMH/SH8 manual
Bad relay ? What makes you think that ?
The integrated furnace board controls the blower speeds.
The blower should only work in two speeds if the optional relay was installed.
Try running the blower on FAN ONLY and see if it has the same problem.
Goodman GMH/SH8 manual
#3
06-12-19, 06:09 PM
Member
check your thermostat wiring, make sure wires on y are secure on furnace circuit board.
if the board doesn't sense y it will run on the continuous fan speed, may be a marginal connection.
if the board doesn't sense y it will run on the continuous fan speed, may be a marginal connection.
#5
06-12-19, 06:26 PM
PJ. Thx for quick reply. Yeah, I knew the relay was a bad guess. Just has me baffled to why its randomly going from high to low blower during cooling.. Its listed as a variable speed furnace but I think that's only for heat mode... I`ll put it in fan mode and get back to ya. Thx!
#6
06-12-19, 10:05 PM
Member
the gmh has a regular blower motor to my knowledge.
with a multi-meter or multi-meter, you can see which speed terminals are being energized.
Can also direct jumper R and Y together at the board as well as R and G to rule out some odd thermostat issue.
If the board is getting proper line voltage input, low voltage (24v ac +/- between R and C, as well as between Y and C with a call for cooling) and its switching between speeds without the thermostat input changing, its bad.
If you bought the furnace online, you'll have to contact your supplier to try and warranty the board. Goodman won''t deal with diy installed stuff.
with a multi-meter or multi-meter, you can see which speed terminals are being energized.
Can also direct jumper R and Y together at the board as well as R and G to rule out some odd thermostat issue.
If the board is getting proper line voltage input, low voltage (24v ac +/- between R and C, as well as between Y and C with a call for cooling) and its switching between speeds without the thermostat input changing, its bad.
If you bought the furnace online, you'll have to contact your supplier to try and warranty the board. Goodman won''t deal with diy installed stuff.
#7
06-12-19, 10:46 PM
Group Moderator
Yes.... that's a standard PSC motor. Double check the board for the fault light showing a code. If a limit switch (or limit switch wiring) was intermittent that could cause a speed change.
#9
06-30-19, 05:29 PM
OK. Figured it out. The "C" wire wasn't hooked up on my Nest thermostat so I connected it to the Nest and the furnace and PROBLEM SOLVED! These smart stats need power to run and without a "C" wire connected, they will act strange. Thx for all the help!
#10
07-01-19, 08:00 AM
Member
Honestly, get rid of the nest thermostat - they have a horrible reputation, known to cause a lot of problems.
