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HEY ALL,

I recently had the blower motor in my 96 sts quit on me. I have a replacement motor for the car, but when i plugged it in to double check its operation, it didnt work. If i plug it into my buddy's deville it works no problem. I checked all fus4es etc, just wondering if anyone has any ideas.

Also is the blower control module parrt of the blower motor itself or is it seperate all together. I looked at a wiring diagram for a 95 sts and it looked like it was part of the blower motor assembly.

Any help would be greatly appreciated, Its freakin hot here!

Matt B)

A good friend will come and bail you out of jail...BUT, a true friend will be sitting next to you saying, "darn...that was fun!"

www.madd.ca

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I know you said you checked all of the fuses...I thought I checked them all when I installed by motor.....but forgot to check the big 50a MAXI fuse up front...Did you check for corrosion on male end of the harness?

A.J.

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Blower operation and speed is controlled by the ACM. It is located behind the glove box and has electrical and vacuum connections to it. Check everything else, twice, it is BIG $$$$$

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here is an update,

i double checked all fuses, i do have power to the connector at the blowermotor, but should i be getting some sort of voltage from the middle pin on the connector itself, i know one is a ground, and one is constant power, but when i hook up the dvom to the middle pin i get no reading, any ideas what that means??

Matt B)

A good friend will come and bail you out of jail...BUT, a true friend will be sitting next to you saying, "darn...that was fun!"

www.madd.ca

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The ACP pulls the 'middle pin' terminal to ground, so you won't measure anything there. The voltage on this speed regulation circuit must be measured in-situ (i.e. while connected to the blower). If this circuit stays high, the blower will not run. To rule out a wiring fault, you might want to check for continuity between this terminal and the corresponding terminal at the ACP connector.

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addison_ii is correct. The connector is notorious for developing poor connections due to heat fatigue. Double and then triple check it!

Here's some info from the 1995 manual. It may apply to your '96.

Electrical drawing: http://i7.photobucket.com/albums/y299/WBucket/BlowerDWG.jpg

Trouble Chart: http://i7.photobucket.com/albums/y299/WBuc...BlowerCHART.jpg

From the troubleshooting chart you can see that the middle pin should read around +9 voltswith the motor off and close to +4 volts when the motor is on a tear. HTH.

Regards,

Warren

EDIT: Yes, the motor speed control circuitry is part of the blower motor *smurf*'y. It gets its speed command as a pulsating variable duty cycle DC voltage (PWM) from the ACP. The ACP, in turn, gets the speed command in the form of DATA from the ICP.

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There is no means of avoiding the final collapse of a boom brought about by credit expansion. The alternative is only whether the crisis should come sooner as the result of a voluntary abandonment of further credit expansion, or later as a final and total catastrophe of the currency system involved. - Ludwig von Mises

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You can verify the speed control signal on the thin wire (middle) by connecting a 1kohm resistor between the middle pin and the positive on the harness connector. Then probe with a v-meter the potential of the middle pin to ground (black big wire. It must be low with the blower commanded ON (not zero though, it is pulse modulated) and high with the Climate Controll in OFF.

Heat damage happening out of the blue, usually on a hot day with an important passenger in the car, is possible too, but i guess that would be clearly visible (in my etc the connector melted together nicely in one brittle blob).

You may want to check the blower mot before removing it from the car, to save you effort in case the trouble is somewhere else, by feeding battery power directly to the motor's pins and grounding the middle pin.

good luck there!

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You can verify the speed control signal on the thin wire (middle) by connecting a 1kohm resistor between the middle pin and the positive on the harness connector. Then probe with a v-meter the potential of the middle pin to ground (black big wire. It must be low with the blower commanded ON (not zero though, it is pulse modulated) and high with the Climate Controll in OFF.

That sounds like an excellent troubleshooting technique, assuming 1,000 ohms is the correct value for this application.

When you speak of HIGH or LOW, I'm reminded of the troubleshooting chart which seems to indicate that +9 volts is HIGH (motor off) while +4 volts is LOW (motor is makin' large RPMs). Intermediate voltages, presumably, would correspond to intermediate speeds. I'd guess a very low wattage resistor would suffice.

Heat damage happening out of the blue, usually on a hot day with an important passenger in the car, is possible too, but i guess that would be clearly visible (in my etc the connector melted together nicely in one brittle blob).

The humor is appreciated, however, the blower motor connector IS notorious for developing poor contacts due to heat fatigue. NOT kidding! :P Additionally, it is known that blower motor electronics may fail due to careless placement of the spark plug wires.

You may want to check the blower mot before removing it from the car, to save you effort in case the trouble is somewhere else, by feeding battery power directly to the motor's pins and grounding the middle pin.

I would advise doing this with the connector REMOVED from the motor. Let's not surprise the electronics!

EDIT: That said, however, let's NOT forget that Matt plugged in a replacement motor only to find that it didn't go 'round in circles.

Regards,

Warren

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There is no means of avoiding the final collapse of a boom brought about by credit expansion. The alternative is only whether the crisis should come sooner as the result of a voluntary abandonment of further credit expansion, or later as a final and total catastrophe of the currency system involved. - Ludwig von Mises

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You can verify the speed control signal on the thin wire (middle) by connecting a 1kohm resistor between the middle pin and the positive on the harness connector.

I think you meant to say to connect to ground on the harness connector (the middle terminal on the blower via the 1K resistor). :)

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You can verify the speed control signal on the thin wire (middle) by connecting a 1kohm resistor between the middle pin and the positive on the harness connector.

I think you meant to say to connect to ground on the harness connector (the middle terminal on the blower via the 1K resistor). :)

No . . . . I think he meant what he said.

Regards,

Warren

Posted Image

There is no means of avoiding the final collapse of a boom brought about by credit expansion. The alternative is only whether the crisis should come sooner as the result of a voluntary abandonment of further credit expansion, or later as a final and total catastrophe of the currency system involved. - Ludwig von Mises

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I think you meant to say to connect to ground on the harness connector (the middle terminal on the blower via the 1K resistor).  :) 

No  . . . .  I think he meant what he said.

Remember that the ACP pulls this control lead to ground. If you connect B+ and Gnd to the blower, it will not run because the control lead remains high. To simulate the action of the ACP, it is necessary to ground the 'middle' terminal via a resistor; lower resistances correspond to a higher blower RPM.

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I don't belive the ACP pulls the center lead to ground per se, I have scoped mine and find the pulse width modulation pulses to be there and they change in frequency and amplitude when you turn the ACP from low to high. I found my ground to be open. to verify this, just use a voltmeter and put the minus to ground and the positive probe to the black ground wire on the motor plug. If you read any voltage at all, the ground is missing. I just broke the line in two and attached another to them with a wire nut and secured the new wire to a good ground. I think I used the cross brace mounting bolt. Not a problem any more. You can also take an ohm reading to ground with the plug disconnected from the motor and you should read "0" ohms. So, in my opinion the only sure way to troubleshoot this system is to use an oscilliscope and a VOM.

1. there should always be 12 volts on the red wire at all times (even with ignition off).

2. There should always be a good ground connection.

3. With the aid of an oscilliscope you should be able to see the pulses and the should change in amplitude and frequency when the ACP is changed from low to high.

If all three conditions are metl, I would suggest changing the motor. In the 94 to 98 models, the motor can be removed by first removing the connector, then the three bolts on the thick back plate and then remove the plate and then remove the outside mounting screws (about 7 of them and not easy to get to. Then the motor can be moved back about 2 inches and at this point it can be pried apart into 2 pieces. There are three long prongs that connect the plug to the motor itself and they just push in. You will also have to unplug the wiring harness's and unsnap them from their plastic clamps and remove the PCV vacume line and the first 2 spark plug wires. Be careful and remove it gently so as not to break or dislodge the squirrel cage. To reinstall it, first insert the motor with squirrel cage in the hole and then attach the plug module and then attach the heavy back plate and bolt it home with the 3 bolts and then install the unit and replace the outside screws and plug it in and reconnect all items removed for removal and installation.

Hope this helps someone out, I spent a lot of time and research and testing to come to this conclusion........luck

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In previous messages, I've stated that the ACP pulls that circuit to ground in a PWM fashion. I was brief in the recent post in order to emphasize the direction of current flow. It is not necessary to use an oscilloscope to diagnose properly this system; just follow the directions in the service manual. The purpose of the PWM is to regulate the potential on the control circuit, since the blower circuitry does not respond to frequency, just the net result.

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  • 2 months later...

TTT. There's a host of good info in this thread and have a question...

I pulled my blower motor out and one of the windings is toasted. I was going to rewind it, but I assume that for the winding to burn, something else would have had to fry. I got the controller circuit separated from the winding housing...this is the worst luck I have ever had at desoldering though. I figured I would test the transistors first and the caps next.

With the motor hooked up but the cage removed, 2 of the 6 junctions that the magnet wire attaches to read 1-24VAC regardless of the speed selected on the CCP. The other 4 terminals read between .5-1VAC, again, regardless of the CCP selection.

Has anyone else attempted to rebuild the contol portion of the motor itself? All parts could practically be replaced for about 30 bucks and I hate shelling out $225...it is just difficult for me to determine what values the other junctions that the magnet wire attaches to should be reading, so even if I 'fix' it, I won't know if it is fixed necessarily.

Any responses welcome, although 'just buy a new motor' probably won't persuade me just yet unsure.gif

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TTT. There's a host of good info in this thread and have a question...

I pulled my blower motor out and one of the windings is toasted. I was going to rewind it, but I assume that for the winding to burn, something else would have had to fry. I got the controller circuit separated from the winding housing...this is the worst luck I have ever had at desoldering though. I figured I would test the transistors first and the caps next.

With the motor hooked up but the cage removed, 2 of the 6 junctions that the magnet wire attaches to read 1-24VAC regardless of the speed selected on the CCP. The other 4 terminals read between .5-1VAC, again, regardless of the CCP selection.

Has anyone else attempted to rebuild the contol portion of the motor itself? All parts could practically be replaced for about 30 bucks and I hate shelling out $225...it is just difficult for me to determine what values the other junctions that the magnet wire attaches to should be reading, so even if I 'fix' it, I won't know if it is fixed necessarily.

Any responses welcome, although 'just buy a new motor' probably won't persuade me just yet unsure.gif

The blower motor in my '96 SLS failed three years ago. I could see that one of the MOSFETs was toast as well as a couple of electrolytic capacitors. I replaced all the visibly defective components and reconnected the blower. It spun back and forth like a washing machine and then started smoking...

I ordered a replacement blower and everything has been fine. In my opinion, it's not worth attempting to repair the blower - just replace it.

Kevin
'93 Fleetwood Brougham
'05 Deville
'04 Deville
2013 Silverado Z71

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I know you don't want to hear this, but there's a caddy dealer on eBay that sold me my blower motor for $182.00 including shipping that comes with the standard Cadillac 1 yr. warranty-good at any dealer. They are a legit Cadillac dealer from IL.

His seller ID is: gm-delco-parts-direct

I don't see any motors listed there now, but you can call them at 708-848-7600 and ask for Ed at parts. He's a real nice guy.

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Thanks for the replies.

So far, just one of the caps is bad (the big 50V 470uF), didn't have a chance to spend more than a few minutes with it though so I didn't get to the transistors.

I need to get the conformal coating off so I can see what other parts of the circuit might have gone belly up.

That's the best price I have seen so far on a motor. I found one for $220 with a lifetime warranty...not sure how long I am going to keep my DeVille.

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I could see that one of the MOSFETs was toast as well as a couple of electrolytic capacitors. I replaced all the visibly defective components and reconnected the blower.

You got much further than me so far. I've got a bad 50V 470 microfarad cap and about the only other thing that could go bad on that leg (other than the 24pin) is the transistor. I put in a new cap and walla--it blew as expected. After scraping off the conformal coating, I have not been able to cross reference the transistor. My numbers are M_8699 and R9634...which I am assuming is a date code.

One of the other good (maybe...) transistors has the same M number but a different R number.

Did you guess or were you able to crossreference?

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I could see that one of the MOSFETs was toast as well as a couple of electrolytic capacitors.  I replaced all the visibly defective components and reconnected the blower.

You got much further than me so far. I've got a bad 50V 470 microfarad cap and about the only other thing that could go bad on that leg (other than the 24pin) is the transistor. I put in a new cap and walla--it blew as expected. After scraping off the conformal coating, I have not been able to cross reference the transistor. My numbers are M_8699 and R9634...which I am assuming is a date code.

One of the other good (maybe...) transistors has the same M number but a different R number.

Did you guess or were you able to crossreference?

Another member named Emil repaired his blower motor successfully. He provided the cross reference. You might search the old board's archives as that's where the information is likely to be found. I ordered the MOSFET from Digi-Key but the paperwork is long gone...

Kevin
'93 Fleetwood Brougham
'05 Deville
'04 Deville
2013 Silverado Z71

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Two quotes from the archives:

"Each motor's phase is driven by a N-channel mosfet in TO220 full-pack (plastic with plastic tab). In my blower motor one of these fets croaked. The marking is M8699 and below R9615. Good luck crossing this one. Oh well, any decent >50V/20A N-channel should do, but I have to wait for the electronics parts store to open.."

"IRLI2505 from International Rectifier. Approx $6 at DigiKey."

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Woah...I've been trying to get to the archives and have come up empty (starting from http://www.caddyinfo.com/ and then going to old board/searchable archive)...I even tried http://www.archive.org/ and it had the main pages, but none of the threads were searchable.

Thanks, both of you! Now I just have to rewind and solder...and hope for spinning only one direction biggrin.gif

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Keep usw posted on your progress. Hopefully you will be able to repair the blower.

Kevin
'93 Fleetwood Brougham
'05 Deville
'04 Deville
2013 Silverado Z71

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<<I recently had the blower motor in my 96 sts quit on me. I have a replacement motor for the car, but when i plugged it in to double check its operation, it didnt work. If i plug it into my buddy's deville it works no problem. I checked all fus4es etc, just wondering if anyone has any ideas.>>

Matt,

The above makes me think it IS the connector which feeds the fan motor. I had to replace mine and a couple others have suggested that you check and double check the largest female socket. This socket overheats and moves rearward just enough so that it doesn't make connection with the fan motor pin. Please check it again

Jim in Phoenix

Jim in Phoenix

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  • 4 weeks later...
Keep usw posted on your progress. Hopefully you will be able to repair the blower.

No news yet. I was hoping to get my parts locally and only had two chances to pick them up in the last 3 weeks, but they were out of stock. I'm ordering a few things through DigiKey today...hopefully will have them by the end of the week. If things work out, I'll know by Friday if it will be worth rewinding it or not.

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