Heater Blower Isn’t – and It’s January! (1 Viewer)

[TheHardWay]

I don’t know when it crapped out, but two weeks ago when I took Zeb out for a joy ride I pulled out the heater blower knob for a nice hot blast of … WTF! The heater was doing its job, and as long as I was chugging along at 35 – 40 the air coming out the bottom of it was toasty, but that blower was giving me the silent treatment. UNACCEPTABLE!

Now, diagnosing electrical problems (as we all know) is a trial, but I wanted my damned heat, so I hooked my trusty multimeter up to the fuse panel and checked for continuity all the way to the harness connector at the blower end of the circuit. HAH – just as I suspected –

I removed the blower cap and found no damage to the armature, brushes or soldered connectors, cleaned the dust out and reassembled. It must be the resistor. A quick Mud search confirmed other Mudders have had this very problem, so I went ahead and ordered a replacement from Mouser. While waiting for it I removed the original.

I knew from the search threads that the replacement resistor was longer than the original, and that the mounting bracket would have to be replaced, so when the resistor arrived the manufacturing process began.

 

[TheHardWay]

Desoldering the wires was easy with the iron set to 900 degrees. Resoldering to new connectors was too.

I had some bolts just a little longer then the new resistor, so used washers for the fit.

Reconnected the harnesses, turned key to On, pulled out blower knob to first stop and it began blowing – pulled to second stop and it blew faster.

Took a test drive (actually any excuse will do) this morning and when I pulled the fan knob out I GOT A NICE WARM BLAST OF HOT AIR.

I love a diagnosis that leads to a fix! MESOHAPPY

 

[Living in the Past]

Resistor is not needed for high speed. The resistor is what is used for low speed. Before tearing the motor apart apply 12 volts off the positive side of the battery to the side of resistor with two wires, one from the harness and one going to the motor and then ground off the battery to where the other wire from the motor terminates is a quick way to test the motor without a meter.

Factory wired first position when the switch is pulled is the high speed. Obviously someone has messed with the wiring before. High speed not working in either position is a continuity issue not the resistor.

 

[TheHardWay]

Resistor is not needed for high speed. The resistor is what is used for low speed. Before tearing the motor apart apply 12 volts off the positive side of the battery to the side of resistor with two wires, one from the harness and one going to the motor and then ground off the battery to where the other wire from the motor terminates is a quick way to test the motor without a meter.

Factory wired first position when the switch is pulled is the high speed. Obviously someone has messed with the wiring before. High speed not working in either position is a continuity issue not the resistor.

Huh, I must be misinterpreting page 19 of the Owners Manual:

The drawing of the Fan Pull knob above - looks to me like first stop is low speed, and second stop is high speed. No? If that's the case, then the other two 40s I've owned were also monkey wired, because they both pulled to the first stop for low.

 

[Skreddy]

My 70 and my 71 were 1st pull= high speed, 2nd = low. Both front and back heater blowers. But my cowl fresh air pull is also opposite of the manual so who knows.

 

[red66toy]

Great work! Clean repair

 

[Living in the Past]

My 70 and my 71 were 1st pull= high speed, 2nd = low. Both front and back heater blowers. But my cowl fresh air pull is also opposite of the manual so who knows.

Have a 68 and 70 that both operate the opposite you think they should. My 73 owner's manual show low first than high but the wiring is so hacked who knows original switches and heater were removed for A/C and aftermarket heaters. I notice shows front heater closer to the driver. My 68 and 70 the rear heat switch is closer to the driver. It's almost like it's a LHD vehicle put together in a RHD market.