Hello all. I've got a problem where the blower motor wont work unless I hook up a direct ground to the blower motor. Then of course you loose high speed. Not a huge deal but I did get it working in every speed for a while. It would not turn off though with the key on. I was looking for a short to power and ended up unplugging a plug at the firewall which killed the blower motor. I was not able to make all the speeds work again after that, I had to wire up the non stock ground wire again. Just wondering if its a common problem and where I should look next. Thanks for your help all.
My car 84 Z28 formerly A/C car. Now a carb'd 350. Let me know if you need more info.

 

Hooking a direct ground up to the blower shouldn't loose you high speed. It's the positive side that controls the speed of the blower, the ground should always be present. Was the blower on full blast when you were having the always-on issue? It could be the high-speed relay was sticking which would cause that since it would bypass the switch. If it's not running at all, and you have everything plugged in, then there's several places it could be failing. For the blower, power flows through the heater/AC fuse (25 AMP), into the vent selection switch, through the blower speed selection switch, then through the blower motor resistor set or relay depending on the setting. So first check the fuse and make sure it's good. Do you have a multi-meter?

 

There's supposed to be a ground wire on the blower motor frame to begin with, from the factory. Has to be: the thing it bolts to is plastic and doesn't ground it otherwise. Only way hooking up another would matter is, if the original one is missing.

Go ahead and make sure your blower is thoroughly grounded. That CANNOT cause any problems and is in fact REQUIRED for it to work.

All of that about "short to power" and "unplug at the firewall" makes no sense. Put all that back together, along with verifying that the blower ground is secure and that as mentioned the HVAC fuse is good, and tell us what happens. We'll point you in the next direction.

 

Sounds kinda like you may have a bad blower motor resistor.

 

Update: Drive to work, with low and medium speeds working. High turned it off. On my drive home I noticed the fan was working in all speeds with the position selector in off. Would not turn off as long as the key was in run. Hooked up all of the factory wiring. Same problem. All speeds work, won't turn off unless you turn the ignition off. Fuse is good. I do have a multimeter. The a/c or vent selector switch seems not to affect the blower in any way. Thanks all.

 

Kinda a bunch of inscrutable mumbo-jumbo...

Clarify:

Sounds like it works PERFECT except high speed is out. Turn the key on, all 3 lower speeds work, works like it's supposed to until you turn the key off, at which time it turns off, like it's supposed to. High speed is out.

??? Is this an accurate summary of the situation?