Blower motor issue
 

I’ve got a 1984 C10 and over the weekend my heater blower stopped working. I’ve been chasing wires a trying to see what happened and I discovered that the fuse for the blower is grounded. It didn’t pop or anything, but when I hook up my test light to it, as in the alligator clip side to a positive lead and the probe end on the fuse, it’s grounded. Is that correct? Doesn’t seem right.

If not, anyone have any idea why or how that happened and what I can do to fix it? Let me know if any further information is needed. Thanks in advance!

Re: Blower motor issue
 

If you have the alligator clip hooked to a 12+ source and the probe end to the fuse and the heater switch is in the fan run position the test light should light as the probe is finding ground through the fan motor.

I'm not familiar with the early 80's C10 heater circuits but I am familiar with the late 80's and early 90's S10 circuits. I can't imagine they are very different.

I would start by disconnecting the blower and with the test lights alligator clip on the battery's negative post put the probe in the rubber connector that was connected to the blower. If things are working correctly you should be able to see differences in the test light as you cycle through the different settings on the blower control. If you get no light and your positive the fuse is good carefully inspect the connector as they can break inside the rubber boot.

If that appears to be good move the probe to the purple wire on the resistor mounted on the heater box and test again.

If still no light move the probe to the tan wire on the resistor. Here you should have the light on with the fan speed in low.

If still no light ad you know the fuse is good then you will need to pull the heater controls. My S10 knowledge probably won't help you as the switches are different switches.

Over the years that I've owned S10's I've had numerous blower switches fail, 2 of connectors at the blower motor fail and one resistor fail. If you inspect the blower control you should be able to visually see if it has overheated and failed.

I hope this helps.

Re: Blower motor issue
 

1st place I would look is the blower resistor. Comes out with 2 screws. Normally you just lose a speed but it can fully open as well.
Also look inside the blower resistor connector for melting.

If an AC truck, theres a relay mounted to the evaporator box that feeds power to the blower resistor. But start with the resistor.

Re: Blower motor issue
 

Do you have AC in your truck or just the heat controls?

Re: Blower motor issue
 

Re: Blower motor issue
 

Thank you everyone for the replies and help, I greatly appreciate it.

I replaced the resistor and the relay and neither fixed the issue. After tracing wires and diagnosing problems, I’ve discovered that I’ve got a short somewhere beyond the HVAC system. The orange accessory wire coming from the steering column is grounded, and that’s as far as I’ve gotten at this point in time.

If anyone has any idea why or where that wire is getting ground from, I would greatly appreciate any insight. Thanks again!

Re: Blower motor issue
 

Pull the motor and test. A locked up motor or one that isn't spinning can appear as a ground to test instruments.

Motors can quit spinning because of mouse nests clogging up the works or just because it goes bad.

Re: Blower motor issue
 

The blower starts blowing when 12V is applied to the terminal.

Question for everyone; is the little stud on the starter supposed to be grounded? (Pic attached for reference)

My test light is showing that stud that the smaller wire attaches to to be ground (with the starter still in the truck obviously, key on or off).

Is it possible something within the solenoid has broken and that stud is now supplying ground rather than 12 volts?

Re: Blower motor issue
 

Re: Blower motor issue
 

Re: Blower motor issue
 

I thought maybe that circuit drew power from something to do with the starter. Not too great with electrical.

Long story short, I found the issue. There was a short in the horn circuit that was shorting out the IGN ACC circuit (doesn’t make much sense to me, but it fixed the issue).

Now the new issue I’m having is the fuse for the blower blows when fan speed is on high. Any idea what the heck would be causing that to happen? I replaced the blower relay and resistor while chasing down this other issue. Possible one of those is bad out of the box?

EDIT: I figured it out, it was the brand new relay that was bad. I put the old one back in and the fuse stopped blowing. Imagine that!