Blower motor inop

[dtch]

I'm not getting any sound from the blower no matter which speed it's on. .What are the first steps to troubleshoot?

 

[Rickf]

Have you checked for a blown fuse?

 

[dtch]

Have you checked for a blown fuse?

Fuse looked good. Tested good. Put in a new fuse anyway but no change.

 

[Rickf]

Run a wire from the battery directly to the blower and see what happens. If the blower spins, it's probably the resistor.

www.ebay.com/itm/Heater-Blower-Motor-Resistor-for-Buick-Chevy-GMC-Olds-Pontiac-Car-SUV-Pickup/310550733156?

 

[dtch]

Run a wire from the battery directly to the blower and see what happens. If the blower spins, it's probably the resistor.

They run around $20

Hot lead to the plug does operate it. Sounds like junk but it moves.

 

[1987 GMC Jimmy]

Sounds like junk doesn’t speak to the longevity of what you have, but it does sound like replacement won’t solve your problem. You can check the resistor and swap in a high speed relay if you want to try an easy start. It seems unlikely that the relay and resistor would fail simultaneously. It could also be a wiring problem or a shot speed control switch.

 

[dtch]

Gonna test the switch and resistor tomorrow. If I end up needing a new blower I'm going to do the GMT400 upgrade.

 

[dtch]

Alright so if I put 12v to any of the contacts on the switch itself (with pigtail plugged in) the switch works for all 4 speeds. I'm just guessing here but it seems like the switch is operating and I'm just not getting power to the switch?

 

[Matt69olds]

If the motor runs but is noisy, replace the motor first. If the motor pulls excessive current to run, it will burn up the relay nd possibly melt wiring. The fuse in the fuse box powers the motor on the lowest 3speeds, when you put the switch in the high position the relay bypasses the resistor block and supplies full battery voltage to the motor.

 

[dtch]

Thanks Matt. I'll order in a new motor this weekend.

 

[Charlie]

I replaced blower motor on a 68 and 74 C10 and napa had one for each of them.

 

[75gmck25]

Its been a long time since I did the work, but I think it took a couple trips to the parts store to get the right blower motor and squirrel cage. The parts catalog at Advance Auto Parts listed multiple choices for my '75, with minimal explanation, so I had to compare old to new to get the right replacement. My truck has HD heater and A/C, so maybe the housing or motor are a little different than the base models.

Also, on an A/C truck the high speed blower usually has a separate fuse and relay under the hood, while the low speeds run through the fuse in the fuse panel. That relay mounted on the plenum allows GM to kick on high speed when the A/C is at the max setting.

Bruce

 

[themdg]

I found this vid to be very useful in understanding how it should work, and how to trace the circuit.

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In my case, I found that mine was actually unplugged right at the blower motor. When I plugged it in it sounded awful, didn't blow much, and didn't work on the highest setting. Based on that video, I'll be looking at a bad resistor (for the high setting) and a worn motor.

 

[1987 GMC Jimmy]

The resistor controls the three lower speeds, and the relay the max speed.

 

[norman baker]

I'm not getting any sound from the blower no matter which speed it's on. .What are the first steps to troubleshoot?

check the top of the heater box 3-4 prong plug , if you have power there on high , run a wire to the blower wire aka jumper , if it runs , look farther inside .