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'16 VSport (wife's), '10 Escalade, '97 & '02 SS Camaro's, '15 Silverado LTZ
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Discussion Starter #1
Hey guy's, been a while since I've been on. Been really busy which is a good thing with the economy as tanked as it is.

Anyhow... The wifes '97 STS HVAC blower motor will not operate. She says she can hear the compressor cutting on and off just no blower operation. Any ideas to check for first? I did check the red hot wire at the plug (at the fan motor) and it is 12v.

Thanks for any advice in advance.
 

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1926 Model T street rod, 2000 Jaguar XJ8, 1999 Corvette.
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6,738 Posts
If you have voltage then you need to provide a good ground to verify fan motor is good. If, with a ground, it still is inop, I would suspect the fan power module.
 

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1997 SLS
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550 Posts
Is it the original blower? If so, it's probably shot...mine went out 18 months ago and there are many threads here on how to change it out. Not a fun job, but doable.
 

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2010 DTS
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87,556 Posts
Blower failure is somewhat common. Enough so that they where redesigned. See my post in the Tech Tips section on how to replace it. It was for a Deville, but I think it is pretty much the same.
 

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'16 VSport (wife's), '10 Escalade, '97 & '02 SS Camaro's, '15 Silverado LTZ
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Discussion Starter #5 (Edited)
If you have voltage then you need to provide a good ground to verify fan motor is good. If, with a ground, it still is inop, I would suspect the fan power module.
Sorry, a little confused.... Could you be more specific?

If I unplugged the harness and applied battery power to the red wire motor terminal and grounded the black wire motor terminal shouldn't the fan come on if its good? I tried this and got nothing.

I would suspect the fan power module.
Where would this be located? Are you talking about the dash control unit?



Thanks for all of the replies guys!
 

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2010 DTS
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The fan speed is controlled by PWM (Pulse Width Modulation). I think it ranges from .03v - .09v. If I remember correctly, putting 12v to it won't do anything. Don't quote me on this, but I think there are 3 wires? One = Grnd. One =12v and the other is PWM.
 

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'16 VSport (wife's), '10 Escalade, '97 & '02 SS Camaro's, '15 Silverado LTZ
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Discussion Starter #7
The fan speed is controlled by PWM (Pulse Width Modulation). I think it ranges from .03v - .09v. If I remember correctly, putting 12v to it won't do anything. Don't quote me on this, but I think there are 3 wires? One = Grnd. One =12v and the other is PWM.
Would the PWM be the same as the ACM? I checked the troubleshooting chart and tested the connection terminals: A (ground), C (red) and was 14v and B (grey) and was not greater than 4 volts. It's starting to look like the ACM has failed.
 

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2010 DTS
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When my '97 failed all signs from the FSM pointed to the ACM, but my gut told me otherwise. ACM's are very expensive and very reliable. Blower motors are not. I went with my gut and it payed off.
 

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'16 VSport (wife's), '10 Escalade, '97 & '02 SS Camaro's, '15 Silverado LTZ
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Discussion Starter #9
When my '97 failed all signs from the FSM pointed to the ACM, but my gut told me otherwise. ACM's are very expensive and very reliable. Blower motors are not. I went with my gut and it payed off.
Funny..... My gut tells me the same thing :D....... I guess I'll take the gamble and put one in. The wifey has grown tired of this car and has an inkling for a BMW. I can't see dropping all that money on a newer car since this ETC has only 59,800 miles on it and immaculate (no kid wear) and always garaged. She's had it since '98 when we bought it as a lease off with 16k on it. The blower motor is much cheaper than one car payment on the BMW.

I'll follow up with an update once I swap it out. I only wish others would do the same most cases.

Thanks Ranger!
 

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'16 VSport (wife's), '10 Escalade, '97 & '02 SS Camaro's, '15 Silverado LTZ
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Discussion Starter #10
ACM's are very expensive and very reliable. Blower motors are not.
Where is the ACM located and what does it look like? I pulled the glove box and really didn't see anything other than the cable and air directional doors.
 

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2010 DTS
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It in that general area. It has both electrical as well as vacuum connections on it. Probably 5 or 6 vacuum lines.
 

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'16 VSport (wife's), '10 Escalade, '97 & '02 SS Camaro's, '15 Silverado LTZ
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Discussion Starter #12 (Edited)
The fan speed is controlled by PWM (Pulse Width Modulation). I think it ranges from .03v - .09v. If I remember correctly, putting 12v to it won't do anything. Don't quote me on this, but I think there are 3 wires? One = Grnd. One =12v and the other is PWM.
Maybe I'm missing something and someone can chime in. Looking at the wiring diagram it appears going to the motor you have the 1) red 12v constant, 2) grey wire which appears to be grounded then going through the resistor in the ACM, and 3) black ground.

Shouldn't you be able to run 12v to the red terminal (A), ground the grey terminal (B) and ground to the black terminal (C) to make the fan motor run if it's operable?
 

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'16 VSport (wife's), '10 Escalade, '97 & '02 SS Camaro's, '15 Silverado LTZ
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1,132 Posts
Discussion Starter #14
I picked up a new design BM today. I set the fan speed on low, switched off the ignition, plugged it in and, held it while the better half cranked up the car. IT WORKED. Now the tedious task of swapping it out.

Thanks for the comments and suggestions!
 

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'16 VSport (wife's), '10 Escalade, '97 & '02 SS Camaro's, '15 Silverado LTZ
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Discussion Starter #16 (Edited)
Go to the Tech Tips section and read my tutorial on changing it if you haven't already.
I did, very good write up and informative. Thanks for all of the advice and tips....

I completed the job from start to finish in about an hour and 45 minutes including a 5 minute or so break 3 or 4 times to give my back a chance to recover. My back just can't take it anymore. Used too, I could spend hours under the hood wrenching. I didn't have to jack the motor or anything. I unbolted and unplugged everything out of its path, unbolted the metal cover plate, put one of the cover plate bolts back in to keep it all together for removal, rotated the motor until the widest flat edge was centered in the 6 o'clock position perpendicular to the block, tilted the back side up wards and she came right out. I did have to deal with the wiring harness interference coming out and back in but no biggie. I put the new one in the same way. The fan was a little tight going in the hole at that angle but I just used what little flex it had in it working the edge into the hole and she went in. I got everything bolted back up, smoke tested and alls well :bouncy:


According to ShopKey Estimator it's a 2.9 hour job at the dealership :hmm:


The better half will now have to wait a little longer for that 530 BMW she's been wanting :histeric:
 

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2010 DTS
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I completed the job from start to finish in about an hour and 45 minutes including a 5 minute or so break 3 or 4 times to give my back a chance to recover. My back just can't take it anymore. Used too, I could spend hours under the hood wrenching.
Roger that.
 

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97 STS
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20 Posts
@Ranger

Thanks for your post on 06-05-09, 07:50 PM . It saved me a ton. I was stuck on this same problem with my 97 STS. I was using the wrong type of meter (did not go below 1v DC) to check the PWM (Grey/Black) wire. After reading your post (that I found by googling the problem), I borrowed a better meter and found the problem. I was ready to replace an ACM to the tune of $400 + and wound up only needing to replace the blower motor. Bought one from a salvage yard for $85 and bought the lifetime warranty for an additional $5. Great advice. Liked this board so much I had to register.
 

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1996 Eldorado
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2,814 Posts
My experience was the blower would work intermitant then just totally failed soon after.I would some how get it to function manipulating the controls. At the plug (unplugged) I havd batt. volts to the red the black being the ground, the gray 0 volts. Probing the plug connected to the fan, red had batt. volts black gd. and I now had 2 volts on the gray.I checked all speed ranges and this was consistant. Being afraid of the can of worms in the dash I found a used motor on craigslst. for $20 and replaced the fan and all is good and working. These fan motors range in price $200 to $400 for the part. with labor $600 to $1000.
 

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Seville STS 2001, Eldorado 1997
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394 Posts
I had intermittant blower issues (would not work sometimes). I noticed that battery terminals were corroded. By cleaning battery terminals and cable ends, issue has been resolved for seville sls 96

Thanks
John
 
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