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Replaced blower motor resistor & control panel - still no fan on 95 c2500

schiker

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The purple wire comes from the relay/resistors according to fan speed selected. The purple wire should have battery voltage ~ 12V when on hi. At low is might have 5V, M1 7 ish, and M2 9 ish volts. (note mine is not working and I think resistors are bad I get 11.9V on hi 11.73 v on all other speeds lo, m1, and m2.

Anyone ever measure what voltages are normal to speeds ?

Uhhgg I was interpretting measurement wrong in my mind. I was probing purple wire to black and expected voltage drops at different resistors ie speed settings. But with out current flowing through circuit voltages would not drop. V=ir ; no i then no V drop.

Anyway something funny was going on cause new resistors pk shows the same voltage lo - thru hi and OE was different Lo-M2 vs hi and they should all be the same with no current.

Anyway I have my fan working correctly again. It apparently was my motor and maybe my resistors too.
 
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jeff92677

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Hi all, hoping for some help. My 1997 Chevy Silverado CK1500 abruptly changed the way the ac blower fan switch works as follows:

Hi is now Off, Off is now Hi as well as l0.

L2 and L3 are Off.

Blower works, AC works (only on high, but the air is cold and coming from the proper location. Once truck is on and AC button is engaged compressor switches on regardless of blower switch position - maybe that's the way it should be.

I have read these posts, watched youtube videos and followed quite a few others blogs, but none make a reference to this problem. I am guessing the switch or relay or resistor may be shorted out in some way but where to start?

Have you heard of this problem? Any suggestions on how to approach trouble-shooting?
 

bjatle

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FIXED. I replaced the blower, resister and relay before I realized I had power coming from the ground wire at the blower. I grounded the blower under the dash and the first 3 settings worked but no high. So I checked the ground at the blower relay and sure enough 12v. I cut the wire from the back of the harness and grounded it. Now everything works fine.
 

THEFERMANATOR

FRANKENBURBAN
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FIXED. I replaced the blower, resister and relay before I realized I had power coming from the ground wire at the blower. I grounded the blower under the dash and the first 3 settings worked but no high. So I checked the ground at the blower relay and sure enough 12v. I cut the wire from the back of the harness and grounded it. Now everything works fine.
For 95 there is a 2 wire plug, large red and black wires judt behind the glove box. These provide power and ground for the whole hvac system, and they are known to melt, and cause this problem.
 

bjatle

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Thanks you!! Saved me some time runnig a new ground for the whole system. After I got the blower working I figured out I had 12 v at all 3 actuator door grounds. Luckily I seen your post before I started the job. I had already looked at the wiring and didn't see anything. The big red and black wire have a connector behind the glove box. There was no sign from the outside but it was melted together on the inside.
 
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