NEED HELP HVAC blower motor not working

[kwg]

2002 Envoy SLT with Automatic HVAC

I measured the voltage at the fan connector.

With the fan connector unplugged:
Key OFF = 0V
Key ON:
A/C off = 0V
Speed 1thru8 = 3.7V, 5.27V, 6.34V, 7.42V, 8.54V, 9.68V, 10.84V, 12.10V

With the fan connector plugged in:
Key OFF = 0V
Key ON:
A/C off = 0V
Speed 1 = voltage rise to 60mv then falls to 5mv

I assume the blower motor control module is good and the blower motor is bad?

Or could it be a module current issue?

 

[aaserv]

Id ck (as always) for burned terminals in the block but Im thinking/guessing that the windings are bad in the motor. I would go get a motor and without installing it just plug it in to the module and see what happens. If it turns out to not be the motor bring the motor back and exchange for whatever you actually need. Shouldnt be that big a deal. If possible I always recommend after installing the new motor to ck the amp draw and make sure its within specs.....but hardly anyone does..

 

[Mektek]

Check that the fan spins freely. I lubricate the bearings while I have it out.

 

[aaserv]

The motor can have perfectly fine bearings and still have bad motor windings. Most often bad bearings are indicated by a burned module....Thats what makes them burn, the high amp draw required by the bad bearings...and why putting a new module on a motor with bad bearings will burn up the new module quickly.....Hence why I say to ck amp draw on the replacement motor. Some are rebuilt or made overseas where tolerances are quite loose and can pull too many amps right out the box... Usually Id say get the ACDelco motor and ease your mind but at Rock Auto they have a motor for $33 and the ACDelco for $113 so I can understand the temptation to get the cheaper 1......Id just ck the amps after installing the cheap 1 to make sure your not going to be replacing a module and the motor in the not to distant future...

 

[6716]

All I can say is I went cheap on my blower motor replacement this winter and the fan motor is annoyingly loud now. Shoulda spent the extra $20. Might replace yet.

 

[kwg]

I tried a new blower motor and it didn't spin either.

I'm at a loss as to why I see all the correct voltages without
the blower motor connected. It doesn't make any sense to me.

I would replace the MOSFETs in the module if I knew that would help.

My next step is to replace the blower motor control module I guess...

 

[budwich]

you likely guessed wrong on the motor. :-(

you can do a relatively cheap test by replacing the motor with a couple of automotive bulbs connected in series. Then doing your measurements again as you did previously. That will confirm whether the control module can deliver any / enough current. IF you still have the old motor, a simple resistance measurement across the leads and comparing those to the new will also help.