71 Plymouth low volts at heater fan? Help

[400sforever]

When I turn the heater fan on in my 71 Plymouth satellite, it runs extremely slow. i tested the hot wire to the blower motor under the hood and all I get is 10.5 volts no matter what speed I have the interior switch set to. Moving the switch from low, medium, and high also does not change the speed of the fan at all either. I then tested the resistor brown wire in the 3 wire plug at the heater box. It also showed 10.5 volts. It was unplugged from the resistor when I tested it. Moving the fan switch from low,medium, and high also didn’t change the volt reading at that plug wire. So is my fan switch shot or is there another reason I can’t get 12 volts to any of the wiring plugs?

 

[Sinitro]

Blower resistor pack is defective...
Small board on side of heater box Mopar part# 3441822.

Just my $0.02...

 

[Darrah]

It won't explain your lack of different speeds, but that voltage drop is unfortunately pretty "normal" with the crappy electrical connections. If you test the hot going into your heater switch compared to going out, I bet you see a big drop there. Probably another significant drop at the bulkhead. I just fought this a few months ago... the drops over each connection really add up, in addition to creating some heat as a byproduct.

 

[6872n73]

Check the ground wire from the fan also.

 

[MMorgan]

I have similar issue. I have factory air ( not hooked up) fan won’t work with heater button on but works with A/C and max A/C. It runs without using fan switch. 10.7 volts at fan plug.