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heater blower motor not working

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I have a 1998 STS which the heater blower motor is not working. To date i have removed blower motor and connected battery power to center connector and ground to the far left of connector and the motor spun. Not sure on what the third connector does, guessing its a signal wire. Went back to connector and got power to center and good ground on left side and nothing on right thats with the control turned all the way up . No Power or ground continuity. Can someone please send me a wire diagram and any information on the values i should be getting at the wires.

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I'm no that familiar with the '98 blower motor system but it is similar enough to the older cars. The grey wire is the pulse width modulated signal wire. The red and black are the battery and ground. The ACM controls the blower motor in an infinite number of speeds by variation on the PWM signal wire.

It is possible there is an issue with the control head on the dash or the ACM programmer. Someone on this board will have a '98 wiring diagram and a troubleshooting chart they can post.

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

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Thank you for your input. Do you know of a way i can test the blower motor itself to rule out. I put constant power and ground to it and it spins as soon as i plug it in it stops. I feel you are correct, as far as the head unit and the ACM. I checked to see if any of the actuators moved during control movement and i got nothing. Noticed at one time coffee was spilt on controls. I don't drink the java so its been there a while. I just got the vehicle back from my step daughter which she used until she bought her own vehicle. Once again thank you any further information it would be greatly appreciated. Checked the DTC codes got B1341 and B1344 both current.

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I assume your blower motor is on the firewall? am I correct.

98 was the first year of the new body style period for the caddys of your era and alot changed, and I mean alot.

some of the newer ones like the deville it is under the dash on the right side.

From previous experience 9 out of 10 times it is usually the motor. It is PWM controlled and you must be careful probing anything with it.

I suggest 2 things.

First do a battery reset and see if it comes on.

If it does not try plugging in a donor or replacement motor. You dont have to install it to try it but I do suggest putting on the lowest speed for less torque if it kicks on.

Welcome to caddyinfo. best of luck to you


Nice, clean, luxury= fine automobile

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Turned out to to be the connector going into the ACM. I followed the wire from the blower motor to the side of the blower housing and the wire was not making a good connection. I used a zip tie and some electrical to stiffen wire -- all fixed. Passed state inspection. Thanks again.

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