Blower motor help

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Dec 10, 2002 | 02:28 PM

rg0327

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Blower motor help

I have been having problems diagnosing a problem with my fan motor in the heating/AC system. In late summer (with AC on) the fan/ac just up and stopped working. I replaced the 20 amp fuse (in D/S dash panel) to no avail.

Here is what I have checked / replaced.
New blower motor
New selector switch (which I broke trying to check points)
Fan does not work on any fan setting (eliminating resistor as culprit)
Fuse in distribution box is good
Relay (behind Pass side headlamp) functions properly

I get appx. 10 amps of power to the connector at the fan itself with the selector switch in the off position. Once I turn it to any other setting (vent/def/floor) I lose power. This is because the fan motor completes the circuit?

Any help would be great! I am running out of parts to check.

Dec 10, 2002 | 02:40 PM

mathelm

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Joined: Dec 2002

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From: W-S

Blower motor help

Sounds like the heat diode (could be a cap) in the reostat (resistors). Tell me what year it is n I'll try ta tell ya what color wires cross to check it. Or better yet, Take the reostat out (leaving it connected) and short out the heat diode and with the fan on high. But don't leave it like that forever, the heat diode is there for a reason, keeps your truck from burning down. Last one I replaced I got at a junkyard for $5 bucks.

Hope this helps

Dec 10, 2002 | 02:56 PM

rg0327

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Blower motor help

Ok, I don't even know what that would be, so I guarantee that I haven't checked that. It's a '96 (4.0 if it matters).

Where would I locate the heat diode (what would it look like so I can try your suggestion? I'm fairly "green" when it comes to anything this involved so I REALLY appreciate your help!

Thanks again,

RG

Dec 10, 2002 | 03:35 PM

mathelm

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From: W-S

Blower motor help

Ok, took some pics for ya

https://www.ford-trucks.com/user_gallery/sizeimage.php?&photoid=11153&.jpg

This is where its located on my 87. Yours maybe behind the glovebox or under the dash on the passengers side.

https://www.ford-trucks.com/user_gallery/sizeimage.php?&photoid=11152&.jpg

This is the reostat out of a 91 tempo which I think is about the same. This is the one I experimented with and the heat diode is gone, but I drew one in so you'd get an idea of what it looks like. This is what you want to short (see arrows). I used a paper clip.

Hope this helps....

Dec 10, 2002 | 06:30 PM

rg0327

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Blower motor help

Ok, one more piece of the puzzle that is working just fine. I jumped it like you suggested... nothing! I went out and got a Haynes manual since your last message and that hasn't given me much to go off of either. I have one more "test" to try with the blower switch itself, but I think it's a stretch at best. I'll keep you posted.

Thanks a ton!

RG