1995 Cadillac Deville 4.9L heater blower motor not working

Car wiring question

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I own a Cadillac Deville and the blower heater does not work. I took out the blower motor to check it over in the bench and it has 3 wires. I supposed one is for power, another for ground and the third one is for something like a signal. When I feed 12 volts and ground to the 2 wires, it won’t work. Thinking it was defective, I bought a rebuilt one and it did the same. What is the deal here? Can I bench test this rebuilt blower motor?

Vehicle wiring advice

Unlike other gm common blowers, this blower motor has a solid state control device inside to take a modulated variable voltage signal from a programmer (usually heater and ac programmer). This variable voltage is required in order to meet different speed requirements of your vehicle. Unless this input variable voltage is fed, it will not work during the bench test.

So what can you do? If you really want to check if the rebuilt blower motor is working, connect the battery positive and negative terminals direct to the blower motor. Then hook up a jumper wire to the harness where the third (signal) wire come from and it should run. If not, it means your programmer is defective.

Notes

Touching the third wire with a 12 volt supply might damaged the solid state controller inside the blower motor.

What ever you do when working under the dash panel, do not touch the yellow-taped wiring harness to avoid accidental deployment of the air bag which will activate even with the battery disconnected. Remember: you do this service at your own risk.

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