ford truck blower fan only works on high

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Karl
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Joined: Thu Oct 11, 2012 3:43 pm

Re: ford truck blower fan only works on high

Unread post by Karl » Thu Jan 31, 2013 12:39 am

Well that does not make sense that you have power into motor on all speeds, but only high works. I think you are going to have to find a wiring diagram and check the ground circuit for the resistor. Again, high speed does not go through the resistor.
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carriedi
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Re: ford truck blower fan only works on high

Unread post by carriedi » Thu Apr 11, 2013 4:13 am

the brn/orange wire should have power from the blower relay. through fuse 107 = 40a. the orange/blk wire grounds through the blower controls. High by passes the resistor. Going into the resistor is LOW grn/white, MED is yellow/red. ground is the blk wire. orange/black if fan mtr.
fan on high - blk/orange will be direct ground.
fan on medium - yellow and red will be the ground
fan on low - grn/white will be the ground.

turn heater switch to heat with the key on.
with the blower motor switch in the low position touch a fused jumper from ground to the grn/white wire at the resistor. does the fan go on low? if the fan goes on low the resistor and relay are working. you need to look at the control head. If it doesn't the resistor may be bad. they have a thermal protector like a fuse. if it gets hot it blows and it's finished. That's why they put them inside the heater box. so the blower will blow on them and keep them cool.
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