1986 GMC 1987 Chevy No High Speed Fan Blower Motor

1986 GMC 1987 Chevy No High Speed Fan Blower Motor

Postby macsveen [OP] » August 6th 2018, 10:23pm

Hello, I am not getting high speed out of my HVAC blower motor.

I have the lever/slider fan switch, not the twisty knob.

There are four positions, Off, Low, Med and High.

I have replaced the motor, switch, switch connector, the relay above the motor (is there another one?) and the resistor.

I only get Low and Med, no high speed.
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Re: 1986 GMC 1987 Chevy No High Speed Fan Blower Motor

Postby WimpTech » August 7th 2018, 6:56pm

I vote resistor pack... still can loose high if the plug melts and stops making contact. This is quite common actually and was the root cause of the same problem with my GEN2.
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Re: 1986 GMC 1987 Chevy No High Speed Fan Blower Motor

Postby Astro Pop » August 7th 2018, 7:57pm

^^^^What Wimpazz said. On my Gen 2 the resistor I purchased came with a new connectors to splice in. If the connector is looking like it got hot you might need to replace it. Most LAPS carry them, it's that common.

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Re: 1986 GMC 1987 Chevy No High Speed Fan Blower Motor

Postby macsveen [OP] » August 8th 2018, 12:19am

The following is what I did and it worked for a couple of days, but then it stopped and now I'm back to low and medium again.

"As I was fiddling with the switch and connector, I would hear the relay clicking every once in a while.

So, with the key on and the switch set to high, I started jiggling all the wires and harnesses. I moved to under the hood and continued jiggling. As I was doing this I would occasionally hear another snapping sound. That's when I saw the problem.

Behind the battery, underneath some heavy wire harness wraps and covered by a plastic shield, is the "hot connector" under the hood. It has one positive lead that comes off of the battery and other "hot" wires that go to various components under the hood, including what look like three fuse-able links almost under the battery tray. When I jiggled one of those links, the relay would click and there was a spark where that wire made contact to the "hot connector".

I turned off the switch, turned off the key, put a small 3/8" box end wrench on the nut, turned the nut about 3/4 till it was snug and turned on the blower motor to full high speed. Now I know."

Are those fuse-able links repairable?
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Re: 1986 GMC 1987 Chevy No High Speed Fan Blower Motor

Postby Leeann_93 » August 8th 2018, 12:24am

No. Fusable links are replaceable, but not repairable.


Good find, btw ;)
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Re: 1986 GMC 1987 Chevy No High Speed Fan Blower Motor

Postby macsveen [OP] » August 8th 2018, 7:41pm

I have attached two pics.

They are showing the firewall behind the battery, you can see the parking brake cable in the background.

I am pointing out the nut that I tightened and the "fusible links" that I need to test and/or replace. Do the come apart? Do I just cut and splice?

Thanks
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Re: 1986 GMC 1987 Chevy No High Speed Fan Blower Motor

Postby Leeann_93 » August 8th 2018, 9:20pm

I believe they're cut and splice.

I've never had to replace one, so hopefully someone with experience will chime in.
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Re: 1986 GMC 1987 Chevy No High Speed Fan Blower Motor

Postby dennis7815 » August 8th 2018, 10:49pm

My Astro is a 1994 and I have had a great deal of problems with the fused links, normally right at the connector. The links behind the battery fail and the connector is too much trouble to replace so I recommend buy new links at the same rating as factory value and splice and solder the links and coat with liquid tape and after two coats are dry, wrap the splice with # 33 3m electrical tape and connect the link directly to the battery. I realize many people use crimp connectors, but they fail later so solder is best way for durable repair. For your fan issue I recommend you run a # 14 marine grade wire with a fused link right to the fan and enjoy high until you have more time to fix the real problem. On my van I had to replace the high fan speed relay and the ignition switch a few times. The ignition switch has an unfused part that fails when the current is too high. Also on my van I found the factory towing package 105 amp alternator too weak so I replaced recently with a 200 amp alternator made by DB electrical and I have been happy. If I am mistaken about any of this please forgive me, my memory is not 100 percent and I'm over 60 years old. I bought my van new and have had it since 1994 and fix most of the problems on my van myself to save money and sometimes I know my van better then the professional automotive techs that work on all makes and models. I had to take my van to GM tech when the anti shift solenoid on the steering column shorted out and blew fuses on a road trip. The safety switch is buried on the steering column so we just disconnected it until I had time to find a replacement at a salvage yard later. I had the switch installed later by a place that only does steering columns and electrical failures in Hialeah Florida. Let us know how it comes out!
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Re: 1986 GMC 1987 Chevy No High Speed Fan Blower Motor

Postby macsveen [OP] » August 9th 2018, 9:48am

So, I keep hearing about this "high speed relay" or "high speed fuse", where are they?

I have two fuses under the dash next to the parking brake, one is blower, the other is A/C.

I have two relays under the hood, above the blower motor. One is wide and the other is half the width. I believe that the wide one is the blower motor relay and the smaller one is the fuel pump relay. Am I wrong?

I am no longer sure where to go. I do not want to spend $300.00 to replace all the fuses, relays, resistor and links. I fear that I may have more than one failure or that I caused a failure by fixing a different failure. As I said earlier, I replaced the switch and connector, then I found loose nut on the block behind the battery and solved the problem for a day and a half. So, everything worked and then it didn't. Did I blow a relay, resistor or the switch again? Obviously, the relays, fuses, resistor, etc., etc., worked fine, ugh!
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Re: 1986 GMC 1987 Chevy No High Speed Fan Blower Motor

Postby AstroWill » August 9th 2018, 9:37pm

macsveen wrote:I have two relays under the hood, above the blower motor. One is wide and the other is half the width. I believe that the wide one is the blower motor relay and the smaller one is the fuel pump relay.

Correct. Looks like 96582 and the original is black.



macsveen wrote:I am no longer sure where to go. I do not want to spend $300.00 to replace all the fuses, relays, resistor and links. I fear that I may have more than one failure or that I caused a failure by fixing a different failure. As I said earlier, I replaced the switch and connector, then I found loose nut on the block behind the battery and solved the problem for a day and a half. So, everything worked and then it didn't. Did I blow a relay, resistor or the switch again? Obviously, the relays, fuses, resistor, etc., etc., worked fine, ugh!

Going to have to get a meter and a wiring diagram and do some testing. But I would be looking closer at that connection where you found the loose nut. Voltage drop between battery and blower, battery and relay, etc.

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Re: 1986 GMC 1987 Chevy No High Speed Fan Blower Motor

Postby macsveen [OP] » August 10th 2018, 1:28am

Thank you, the under hood stuff is fairly simple, just check for continuity and voltage, etc.

I'm just super done with pulling the dash apart to check the switch and connector. Is there a sure fire way to make sure that the switch and connector stay good? I am so paranoid now that with all this testing and stuff they will burnout.

I can test for continuity from relay connector to resistor connector, correct?

How do I test the switch while having the relay and resistor unplugged? Or, can I?

Voltage drop? What should it be? Is it suppose to drop and to what?

I found a couple of diagrams.

Thanks again
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Re: 1986 GMC 1987 Chevy No High Speed Fan Blower Motor

Postby dennis7815 » August 10th 2018, 6:42pm

IMG_1731.JPG
You can use an inexpensive 12 volt test light to prove if you have power at the fused links and at the ignition switch. I assume you have vin Z? I have vin W. You can test the ignition switch at pin "A". If the ignition switch fails you will also lose the power windows. See photograph attached of the location of the high speed ac relay. The connectors sometimes need to be cleaned with electrical contact cleaner and sometimes unseating the relay and reseating can cause loss of high speed a/c fan. The relay also sometimes black ants get stuck inside between the contacts so you can get the cover off the relay and clean the contacts. You can also get test parts from salvage yard or row 52 dot com. I used label maker to mark my relays as to function to save time. I hope I attached the photographs ok.
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Re: 1986 GMC 1987 Chevy No High Speed Fan Blower Motor

Postby macsveen [OP] » August 10th 2018, 7:54pm

Darn, it looks like I have to get to the switch again.

I was testing and found that I have now lost low speed. I was using the switch with the key on and went from off to low to med to high and only med came on, so as all good technicians do, I jiggled it. As i went from med to high, there was a surge of blower speed. I moved the selector very slowly and sort of pushed and pulled on the lever (finessing it) and I got high speed when the lever was between med and high. I still got nothing on or near low, no matter how much I "finessed" it.

I must have blown the switch and or connector again, ugh, again!

Does anyone know an electrician in East Contra Costa, CA that will work for beer and pizza.
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Re: 1986 GMC 1987 Chevy No High Speed Fan Blower Motor

Postby AstroWill » August 13th 2018, 3:37pm

Sounds like you have found the(a?) problem!

Voltage drop testing information for future reference: https://sites.google.com/site/astrosafa ... op-testing

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