Heater not blowing at all

[1987 GMC Jimmy]

That it does. That lone speck on the firewall - is that a bolt? That flange has got to ground to something because it’s bolted into the plastic heater box. If it were me, I’d get any small gauge wire, put two ring terminals on each end, and run it from behind that bolt in the firewall to in between the closest screw in the blower flange and the flange itself. I’ve never seen a single wire blower motor without some kind of provision for grounding. Either that above or a second prong that a ground wire plugs into.

 

[MisterB]

That it does. That lone speck on the firewall - is that a bolt? That flange has got to ground to something because it’s bolted into the plastic heater box. If it were me, I’d get any small gauge wire, put two ring terminals on each end, and run it from behind that bolt in the firewall to in between the closest screw in the blower flange and the flange itself. I’ve never seen a single wire blower motor without some kind of provision for grounding. Either that above or a second prong that a ground wire plugs into.

It's just a bolt. Might be there as a ground for AC equipped models.

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[MisterB]

By the way, I went to another junkyard today. They had around 10 73-87 square bodies. All of the trucks with AC had a ground wire. Non AC trucks did not. I went ahead and took a ground wire and screws from one of them so I have it just in case I want to attach one

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[1987 GMC Jimmy]

By the way, I went to another junkyard today. They had around 10 73-87 square bodies. All of the trucks with AC had a ground wire. Non AC trucks did not. I went ahead and took a ground wire and screws from one of them so I have it just in case I want to attach one

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That’s very interesting. @gmachinz might know why this is. I sure don’t. Have you had a chance to test the blower directly?

 

[MisterB]

That’s very interesting. @gmachinz might know why this is. I sure don’t. Have you had a chance to test the blower directly?

Not yet. They had a factory tilt column at the yard I took, so I've been playing with that today

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[1987 GMC Jimmy]

Not yet. They had a factory tilt column at the yard I took, so I've been playing with that today

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Lol, gotcha.

 

[Dan Miller]

I had the same prob , Could be the resistor itself , I had one completely burned in half . changed it and it works fine now

 

[Snoots]

Don't the non-AC trucks have a metal box?

Run a wire from the + battery terminal directly to the fan motor. Won't hurt it but will eliminate a 'bad motor' question.
The filter cap leading to the motor may be open. If the motor is good then, plug the cap back in, unplug the cap from the feed wire and then run a wire from the cap to the battery.

That will eliminate a cap problem, if one exists.

 

[MisterB]

I had the same prob , Could be the resistor itself , I had one completely burned in half . changed it and it works fine now

Good to know. Can you point me to where the resister is located?

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[MisterB]

Don't the non-AC trucks have a metal box?

Run a wire from the + battery terminal directly to the fan motor. Won't hurt it but will eliminate a 'bad motor' question.
The filter cap leading to the motor may be open. If the motor is good then, plug the cap back in, unplug the cap from the feed wire and then run a wire from the cap to the battery.

That will eliminate a cap problem, if one exists.

What do you mean by metal box? If you look above, I posted a Pic of my engine compartment. Can you point out what you're referring to?

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[Dan Miller]

It is located in the blower box . Follow your wire harness to where it plugs into the blower box or backtrack from your blower wire . the resistor is mounted by two screws.. cant send pic , I. Am at work

 

[Snoots]

What do you mean by metal box? If you look above, I posted a Pic of my engine compartment. Can you point out what you're referring to?

Post #13
The fan is mounted to a metal box; grounded.

 

[MisterB]

An update on this. I removed the resister (circled and numbered 1). It looked fine. Old, but not burned or out of the ordinary. I cleaned the contact points with steel wool and put some electrical contact grease on the pins. Tried everything, and it still didn't work.

Removed part #2 (not sure what it's called?). Cleaned it, put electric grease on the pins, and then used steel wool on both sides of that ground wire, made sure it was secured and cleaned on the other side, cleaned the firewall behind it, screwed it all down and tried the heater. Nothing.

I don't know. Guess I'll try to test the blower now. That, or how would I tell if the part labeled #2 in my Pic is bad?

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[MisterB]

Don't the non-AC trucks have a metal box?

Run a wire from the + battery terminal directly to the fan motor. Won't hurt it but will eliminate a 'bad motor' question.
The filter cap leading to the motor may be open. If the motor is good then, plug the cap back in, unplug the cap from the feed wire and then run a wire from the cap to the battery.

That will eliminate a cap problem, if one exists.

Do I just take a wire from the positive side of the battery, unplug the plug I circles, and touch the wire there to make contact? It should move the fan if the fan works? Do I need to run any sort of separate ground?

Also, in the second Pic, what is that part I circled? Is that something that goes bad, and if so how do I know if it's bad?

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[Snoots]

Question #1: Yes
Question #2: That is a filter capacitor. It keeps the fan motor noise from getting into the electrical system and messing with the radio. After testing the fan, and assuming it's good, unplug the connector to the right of the capacitor and touch your wire from the battery to that. The fan should work. If not, the capacitor is bad.
Then check (if you have a volt meter) if you have voltage at the pin coming from the resistor pack (with the fan switch on).

NOTE: What I called a capacitor is actually more than that. I used the term capacitor loosley. It's actually a circuit of an inductor and a capacitor.