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Old 07-02-2009, 05:45 PM   #1 (permalink)
Gracie
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Blower fan woes! no ground on black wire on motor?

So I spent most of the day today troubleshooting why the blower motor does not turn!

Bought a new blower resistor and relay. Replaced the resistor (old one looked pretty scummy) and decided to not replace the relay as the old one worked later on.

With the key ON, the controls do nothing. I get no clicks from the relay under the glovebox - the only relay that clicks with the blower knob is the one under the fuse panel on the drivers side of the engine bay and I believe thats the AC relay. The AC system itself has trouble and has a leaky AC compressor (which I also bought a new one to replace!). I broke out the old trusty multimeter and it seems as though the purple wire on the fan motor gets +12v at all times with the fan switch anywhere but OFF. It seems, too, that the black ground wire on the blower motor (accessible from just below the dash) has NO ground potential. I ghetto jumpered a 16 gauge wire from the back of the metal clip on the ground wire to the dashboard impact bar/brace and the fan turns at variable speeds with the knob! All positions of "on" work - low, medium, high, and full blast. So my question is - why does this black wire have no ground potential? I measured about 4.5k ohms resistance between the ground wire on the back of the fan there and the negative terminal under the hood. When I measure the metal crash bar to negative terminal I get like .025k resistance. Much better.

So why doesn't the black ground wire ground? Where does that wire go? Should I just use a 12 gauge wire and jumper the groun to the nearest decent point? I don't really like that the wire doesn't have ground potential and is obviously supposed to. Thanks!
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Old 07-02-2009, 10:03 PM   #2 (permalink)
bk95td
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I had the same problem in my 95LD in my sig. I did the same thing, Ran a new ground to the dash frame. I figured it was a bad connection in the harness somewhere and didn't feel like spending half a day finding it.
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Old 07-02-2009, 10:26 PM   #3 (permalink)
Dieseldad97
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Hey Gracie...welcome to the site BTW.

As for the ghetto jumping, all you did was by-pass the resistor. It's my understanding that if your blower worked fine this way, look hard at your resistor and your connector/plug to and from it. The problem is related to that resistor...I think lol.

Good luck.
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Old 07-02-2009, 10:49 PM   #4 (permalink)
Gracie
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Quote:
Originally Posted by bk95td View Post
I had the same problem in my 95LD in my sig. I did the same thing, Ran a new ground to the dash frame. I figured it was a bad connection in the harness somewhere and didn't feel like spending half a day finding it.
Awesome news - was there any side effect to doing this? I used a ~16 gauge maybe 18 gauge wire and it got a little warm, though I was holding it as best I could and it was sparking for a couple seconds so perhaps it was just my lack of steady connection, but I felt like I should use thicker wire.

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Originally Posted by Dieseldad97 View Post
Hey Gracie...welcome to the site BTW.

As for the ghetto jumping, all you did was by-pass the resistor. It's my understanding that if your blower worked fine this way, look hard at your resistor and your connector/plug to and from it. The problem is related to that resistor...I think lol.

Good luck.
Thanks Dieseldad - I should clarify that this is "Gracie's" son. I posted this on her part because of the more technical stuff that I was testing using the multimeter and such. The truck is actually hers though I will probably be the one to fix it (great!). I don't think we bypassed the resistor because the fan had all its increments. I feel like the fan has no ground for some reason, and we managed to provide that by jumpering the black wire at the fan to the dash crash bar. If I bypassed the resistor wouldn't I have only had one speed?
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Old 07-02-2009, 11:07 PM   #5 (permalink)
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Well then g-day Gracie's son LOL.

If you have power from the red(hot) wire, and you ground out the black wire I'm thinking something is haywire with the resistor. I just finished wasting a bunch of time on Monday going through all this same shit with my wife's Buick Rendezvous. Mind you, we have the dual zone climate control so there was a circuit board on the resistor.

Is there a way to take that muti-meter and double check all the settings on the resistor?

What kind/year of truck you got there? Try a Google search for more info. maybe...
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Old 07-02-2009, 11:14 PM   #6 (permalink)
Green Machine
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This is for my 95



Also... My blower motor hosing is ground as well
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Old 07-02-2009, 11:14 PM   #7 (permalink)
Gracie
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Quote:
Originally Posted by Dieseldad97 View Post
Well then g-day Gracie's son LOL.

If you have power from the red(hot) wire, and you ground out the black wire I'm thinking something is haywire with the resistor. I just finished wasting a bunch of time on Monday going through all this same shit with my wife's Buick Rendezvous. Mind you, we have the dual zone climate control so there was a circuit board on the resistor.

Is there a way to take that muti-meter and double check all the settings on the resistor?

What kind/year of truck you got there? Try a Google search for more info. maybe...
This is a 1995 Suburban K2500 4x4 6.5 TD. There isn't a red wire at the fan. On the blower itself there is a purple wire (+12v whenever the blower speed is anywhere other than 'off') and black wire which should presumably be ground. I have tested the black wire for continuity to ground and theres almost none at all. Some minor transience across the multimeter (something like 4.5k ohms resistance). It was when I jumpered the black wire to a known ground point that the blower started working again. I managed to do this by inserting a wire through the backside of the connector on the blower and then connecting it to the dash crash bar. This effectively grounds the blower and should have no effect on the resitor AFAIK.

I searched around and someone else did something similar... I wish I knew where that black wire is supposed to be getting its ground from so I could trace it out. But, I may just resort to grounding it at the frame there.
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Old 07-02-2009, 11:23 PM   #8 (permalink)
Gracie
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Thanks Green machine! So if I read that correctly, the fan and relay should both be grounding to somewhere in the front right wheel housing? Is it in the engine bay or the passenger side of the firewall?
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Old 07-02-2009, 11:24 PM   #9 (permalink)
Dieseldad97
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Well before throwing a ground wire on, I'd check the switch itself. Just remove the plastic trim and pull the control unit where the switches are and see what's going on. Maybe something is burned up.
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Old 07-02-2009, 11:25 PM   #10 (permalink)
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I would also pull the connector apart (I'm guessing your talking about the one somewhere near the blower motor). Make sure the connector isn't corroded or melted. Mine melted due to having a bad ground i think. It also blew the fuse as i was messing with it.

I can probably get a better wiring diagram... but it won't be until Monday most likely lol.
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