krashx7

I have replaced the blower motor, the resistor, the relay, and ran a new ground wire. Sometimes it will run on high, but not for very long. Ive tried cleaning connectors that look corroded as well. Any ideas on what else to look for? I think the only thing left to replace is the switch itself.. but I wouldnt think that could cause intermittent problems.

87 cutlass supreme

slantflat

High Speed Fan relay. If the fan works on the other speeds but just not high, there's your culprit.

krashx7

hmm.. I replaced the relay though.. I dont get it lol

MDchanic

Just test each component.

Put a hot wire on the High Speed relay for a while.
If it doesn't stop, then it looks like your problem is the switch or the wires in between.
If it still stops, then the switch and wires from it look good, and the problem's probably in the relay or after it.

Proceed from there.

- Eric

slantflat

Right I saw that, but I believe the high speed relay is one unto its own. Or is that the one you replaced?

Looks like the switch is the only thing left.

krashx7

As far as I know there is only one relay. Its right next to the blower motor itself and the resistor. The connectors on everything look really corroded so maybe thats the problem. I tried scrapping them off the best I could..

I appreciate the help Eric but that is beyond my technical knowledge. Thanks anyway

krashx7

http://shop.advanceautoparts.com/buy...66-relays.html

unless theres a seperate relay for high speed other than this guy here

Octania

While any component can fail, every blower motor problem I have ever had was the brushes petered out in the motor itself. The '99 Caravan is on like #5 now. Traditionally fails in med-December.

krashx7

I wonder if there is a fuse some where between the relay and junction box? sigh I give up. I'll just use the next to highest setting.

MDchanic

There are two fuses:
One in the fuse block, which is clearly fine, as the other three speeds work.
The other is an inline fuse between the horn relay terminal block and the High Speed relay. It is one of the many places that can be troubled by corrosion, as you alluded to.

If you have visible corrosion, you need to completely clean it off before you can even consider changing any components.
I prefer a Dremel MotoTool with a tiny wire brush (buy a few and wear safety glasses, as they disintegrate).

- Eric

joe_padavano

You have a high-resistance connector somewhere. The fact that the blower motor works on the low speed settings but not high speed tells us that the motor is probably fine. A common problem on the 77-90 full size and 78-88 A/G body cars is the four pin rectangular connector that mates the engine harness to the HVAC harness. Look for this connector in a harness that runs across the engine, near the distributor on the passenger side of the car. Usually there will only be three wires in the connector, but it has four cavities. The heavy red wire provides power to the blower high speed relay and the terminal in the connector is undersized. Once the terminal gets dirty, it heats up, melts the plastic connector body, and starts to work intermittently and then not at all. I've had this same problem on my 84 and 86 cars.

If this connector is not the problem, the second place to look is behind the heater control panel in the dash. There is a brown wire coming from the blower fan switch that controls the high speed relay. There is a single terminal connector in this wire near the control panel. This terminal also gets corroded, overheats, and melts the plastic connector body. I had to replace that one on my 86.

krashx7

Joe that is very helpful I will look again and see if I can find what you are talking about. Do you have any pictures that will help? Im not sure what the HVAC thing is but I have heard that before somewhere.. Anyway, if it will help I can go out and snap a couple of pictures of my engine in the area you are talking about. I have a 72 olds 455 swapped in. Not sure if that makes a difference or not.

Vistabrat72

There is another little devil to look for which causes many grief: Right around where the horn relay is, there is an old style in-line glass fuse in a round usually black housing. If I can refigure how to post pictures, I will take a picture of it on my '72 Vista Cruiser for you. I don't remember seeing any clear indication of it in the service book wiring diagram either, which adds to the confusion. What this fuse does is act as a protector to the high speed circuit. When I got my car it had no high speed on the heater/AC motor. By fluke tracing wires I found the culprit, the blown fuse! OK, now with you it is intermittent, so I suspect it could be a poor connection of the contacts in the fuse holder to the fuse itself, seeing how you checked everything else! I hope this helps out. Regards, Howie.

joe_padavano

I'm afraid this does not apply to a G-body.