1986 GMC 1987 Chevy No High Speed Fan Blower Motor

[macsveen]

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.

[Herbie]

Sounds like you've swapped all the biggies.

As I understand the high-speed circuit, there's a separate large-gauge supply wire to the relay. That line is fed by a separate fuse. Have you probed that side of the connector to confirm that you have voltage there?

[macsveen]

Yes, thank you for your response. Problem solved.

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.

Thanks again

[Herbie]

Good work!

[Astrophysics]

Hi,

That is very good info. We may all need to snug that connection, especially for the high current load
such as the high speed setting of the blower fan.

Thank you

AP.

Two of my favorite cartoon characters are "Sparky",
and "Ready Kilowatt"

Keep those electrons flowing...

[macsveen]

I spoke too soon.

It worked for a day and a half, then today it did it again, no high speed, ugh!

So, where is this high current fuse? Are those fuse-able links reparable?

I need to recheck continuity on the relay and will get back to you.

[macsveen]

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

[LaGrasta]

Mine is a '98, but I've been chasing this problem for a few years as well. I wasn't aware of these links, expecting my year has them as well. I'll inspect them this weekend, thanks for the information.

Mavens, you asked if they are repairable, short answer is no. But they are easily replaceable. A "link" is only a wire, built to predestruct should an unexpected electrical event occur, prior to the source they supply. You merely splice in a new one, available at any autopart store.