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post #1 of (permalink) Old 02-21-2002, 12:13 AM
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Medium fan speed not working

A friend of mine has a 86 3/4 ton GMC and the medium fan speed has stopped working. The high and low works find so I think the motor is still fine, but i'm not sure what it is. Any ideas. Thanks.

Tim Springer
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1998 Chevy K1500
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post #2 of (permalink) Old 02-21-2002, 12:51 AM
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Re: Medium fan speed not working

well my first hunch would be the switch. I"m not sure how its set up on the older rigs, but tear it apart and see. prolly just a bad contact

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post #3 of (permalink) Old 02-21-2002, 01:01 AM
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Re: Medium fan speed not working

I'm really searching here but my memory is scetchy. I think there is a plug on the firewall that has 3 to 4 prongs coming out of it...well if you unplug it at least. Anyway, mine had that deal where it is always running on low for circulation or whatever, and I took the low speed one (prong) and bent it down and plugged it back in so I didn't have to have it blowing all the time. It could be that his came loose and that is causing it....Or that a connection on the back of the switch came loose.

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post #4 of (permalink) Old 02-21-2002, 01:59 PM
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Re: Medium fan speed not working

i had the same problem with Honda Accord I once had. (It was a quick car phase I went in) Anyway..... it was a resistor that went in the resistor pack. I replaced that and whalla... all fans working. Not sure exectly how the GM's do it but I'd check there. Do a check with a continuity tester to see if its open.

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post #5 of (permalink) Old 02-21-2002, 06:23 PM
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Re: Medium fan speed not working

On the air intake system somewhere around the fan is a plug with three or four contacts. Pull it off and clean it out and stick it back on.

If he's got air conditioning, it'll be on the air conditioning tower just left of the canister.

Since it's not that only high works, then it's not the coils. The way the system works is that on low it goes through all the coils, medium it goes through one less coil, and high it goes through one coil or no coils.

"The difference between a yooper and a lowper is that a yooper oil change involves just changing the filter whereas a lowper oil change involves just changing the oil."
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