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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.
 

SQRBDY87

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Hello all, I'm new to this, so if I'm going about this wrong, my apologies. I kinda have the same issue except when I put the selector switch on high it blows the heater fuse. Can not figure out why. Works on Lo,Lo-med and Med-hi. Once set to high, pop and changing yet another fuse. Thank you for your time and help.
 

Husker6.5

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Hello all, I'm new to this, so if I'm going about this wrong, my apologies. I kinda have the same issue except when I put the selector switch on high it blows the heater fuse. Can not figure out why. Works on Lo,Lo-med and Med-hi. Once set to high, pop and changing yet another fuse. Thank you for your time and help.
Start by checking that plug behind the glovebox if you have a '95 for internal damage that could cause a direct short to ground. Next, with power disconnected/off and the fan speed switch in the OFF position, check the resistance to ground from the HI terminal with the fan control switch harness connector disconnected with a decent digital Ohmmeter. If it's way less than one Ohm or zero, you have a short to ground somewhere, most likely in the switch itself. Next, check the corresponding position for Hi in the harness connector that plugs into the speed control switch. If that reads way less than one or zero, then possibly the short's within the fan motor itself, as the resistors in the fan speed pack provides enough additional resistance to not cause a dead short and blow the supply fuse in the Low (most resistance), Med-Lo (less resistance), Med-Hi (even less resistance, but still several Ohms) switch positions. These beasts are known for bad resistor packs and/or fan motors.
 
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SQRBDY87

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Start by checking that plug behind the glovebox if you have a '95 for internal damage that could cause a direct short to ground. Next, with power disconnected/off and the fan speed switch in the OFF position, check the resistance to ground from the HI terminal with the fan control switch harness connector disconnected with a decent digital Ohmmeter. If it's way less than one Ohm or zero, you have a short to ground somewhere, most likely in the switch itself. Next, check the corresponding position for Hi in the harness connector that plugs into the speed control switch. If that reads way less than one or zero, then possibly the short's within the fan motor itself, as the resistors in the fan speed pack provides enough additional resistance to not cause a dead short and blow the supply fuse in the Low (most resistance), Med-Lo (less resistance), Med-Hi (even less resistance, but still several Ohms) switch positions. These beasts are known for bad resistor packs and/or fan motors.
Thank you for the reply and info. I should have also stated that I'm working in a 1987 Chevy R10, but I'll definitely follow your advice.
 

Husker6.5

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Thank you for the reply and info. I should have also stated that I'm working in a 1987 Chevy R10, but I'll definitely follow your advice.
Yes, telling us what vehicle you have, especially when posting in a thread about a different vehicle, certainly is helpful!

And, welcome to The Truckstop! You'll find a lot of really knowledgeable people on here who like to share their expertise without the attitude or gross misinformation you find on many other forums. We actually have some of the best experts on the GM 6.2/6.5 diesel engine and 4L80E transmission, both theory and experience, in the Country (and globally, we have owners from all over the World on here) on this site.

Yeah, basically you have an issue with either the switch shorting to ground in Hi, a resistor pack issue, or a short in the fan motor for it to be blowing fuses when ran only in the Hi position.
 

SQRBDY87

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Yes, telling us what vehicle you have, especially when posting in a thread about a different vehicle, certainly is helpful!

And, welcome to The Truckstop! You'll find a lot of really knowledgeable people on here who like to share their expertise without the attitude or gross misinformation you find on many other forums. We actually have some of the best experts on the GM 6.2/6.5 diesel engine and 4L80E transmission, both theory and experience, in the Country (and globally, we have owners from all over the World on here) on this site.

Yeah, basically you have an issue with either the switch shorting to ground in Hi, a resistor pack issue, or a short in the fan motor for it to be blowing fuses when ran only in the Hi position.
Than you fir the reply and I will definitely make sure to lead with the type if truck I'm asking about and not "thread jack" like my son stated I did.
 

Husker6.5

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Don't worry about it, thread jacking and thread derailment happens all the time on here - and often by us "old-timers"!

If you could fill out your profile with what vehicle(s) you own, how equipped and what all has been done to it/them, it saves a lot of time trying to figure out things.

You can post all of that signature info and a profile photo if you go into the Settings ‐ Profile and it'll walk you through. That signature stuff all shows up at the bottom of the user's entry if you're using a desktop/laptop or your mobile device in landscape, but if using a mobile device (phone) in portrait all you see is the user's name above the post.
 
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