HVAC Blower Troubleshooting (Page 1/1)
runninwideopen AUG 01, 10:11 AM
Thanks for the add! I’m troubleshooting my HVAC blower in my 88 GT barn find. It sat for 13 years. I’ve already cleaned out the blower and resistor area (actually wasn’t hardly anything in there). I’ve not yet cleaned out the condenser. I wanted to get the electrical functioning first.

Blower wasn’t working on any setting. I think I’ve determined that the High isn’t working because the relays are bad or the connectors are bad. When I jiggle the wires at the relays, it comes on. It got stuck on at one point, but it comes on. New relays on the way.

For Low, M1 and M2 though I can’t get it to work at all. I’ve tested the blower itself, it works. I’ve checked continuity on the purple wire to the resistors. Good. I’ve checked the blower switch. It’s good - I get 12v to each wire on the resistor connector when in the right position. I’ve checked the resistors and I get .5ohm, 1ohm, and 2ohm respectively. Can anyone tell me if these numbers are correct?

If they are correct, what am I missing? Cuz it seems it should be working.

I’m using the Haynes manual schematic - hoping that things correct.

theogre AUG 01, 01:10 PM
Blower has 2 relays in front.
1 for high speed.
2 for all others that turn on by AC control head that allow power to speed knob.

then all go thru C100 bulk connector near gas pedal to the front.

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Dr. Ian Malcolm: Yeah, but your scientists were so preoccupied with whether or not they could, they didn't stop to think if they should.
(Jurassic Park)

The Ogre's Fiero Cave

runninwideopen AUG 01, 01:17 PM
Thanks, I wasn't sure where the C100 connector was.

If I'm getting 12v from the switch to the resistors, that relay and wiring should be working though, correct?
sanderson231 AUG 01, 02:53 PM
Check for 12V with a test light. I have experience where a bad connection showed 12V on voltmeter but would not light a test light.

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formerly known as sanderson
1984 Quad 4
1886 SE 2.8L
1988 4.9L Cadillac
1988 3800 Supercharged

theogre AUG 01, 04:05 PM

quote
Originally posted by sanderson231:
Check for 12V with a test light. I have experience where a bad connection showed 12V on voltmeter but would not light a test light.

Yes, is a sign of burnt contacts. Crap contacts can have volts on a meter, more so w/o a load attach to them, yet have too much resistance to run a motor or much of anything else.

Fiero Blower and some other GM models have a Ground wire attach to them. If that's iffy or dead then same problem as no power.
runninwideopen AUG 06, 01:44 PM
Thanks all. Replacing the relays solved the problem. Blowing strong now! Now to fix the AC........ starting a new thread.