Blower motor switch

[sivlersnake]

I am stumped on this one.
My blower motor started going bad, pulling a lot of amps. Then my switch to control the blower motor, on-off and low, medium, messed up. Now it will not work on low or medium, just high works. I put a new blower motor in and a new switch but it still only works on high. Are there relays or something somewhere in the truck that may be burnt out? I have no idea what to look for.
Any help would be great!

 

[89PSD]

I dont have the answer, but make sure when you connect the blower motor power wires, you connect them the right way... i installed mine with out thinking that i could reverse the direction of the motor spinning.. Long story short it was sucking air from the cab. LOL no heat, very little defrost oops haha

 

[Lost]

What year ? Look right below heater hoes blower in engine bay will be a harness plug unplug remove and replace the switch behind it . When goes bad you will only have HIgh .

Sorry your autoparts didn't tell you about it and save those hard earned funds. Its a common problem

 

[blacksnapon]

Its called a blower motor resistor. When it fails, you only have high. High blower speed is the only circuit that doesn't go through the resistor.

 

[sivlersnake]

Thanks!!
I will check this out tomorrow.

 

[Skandocious]

To add a little clarity here-- the resister should look something like this:

This is an adjustable resistance resistor-- as you turn the motor speed knob on the dash, it adjusts the resistance in this resistor in order to inhibit power to the blower motor and slow down the motor from it's max speed. When it goes bad, it falls back on high speed as a safety feature.

Also of note-- the selector knob that chooses between vents/floor/defrost is a vacuum control, and the system is designed to fall back on defrost if there is a vac leak. Again, a safety feature.

EDIT: To be clear, this resistor works on the ground side of the circuit, not the hot side. (Thanks Vince)

 

[73F100Shortbed]

Like suggested replace the resistor

 

[sivlersnake]

Finally got around to changing the resistor. Now it works like a new one.
Thanks again everyone!!

 

[73F100Shortbed]

Glad you got it fixed up. I don't know about where you are but around here you can't be without heat in the trucks lol.