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Can Bad Blower motor shutdown A/C?

jgcox6 on Mon June 27, 2011 8:26 AM User is offline

Year: 2003
Make: Kia
Model: Optima
Engine Size: 2.7L
Country of Origin: United States

Can a blower motor that is bad cause the A/C compressor not to engage? When I started working on the car, the blower motor was not blowing anything heat or cold. I checked the voltage to the motor and it had 12v that it needed. I ohm the motor out and it is bad...have one on order. I did turn on the A/C and noticed that the clutch is not engaging. I haven't put gauges on it yet..been too busy trying to do other things and it is stinking hot here in Memphis, TN.

Is there some sort of circuitry that would prevent the A/C compressor coming on if the blower motor is not working?

Also can you tell me how many ounces of R-134 this Kia would take if I have to vacuum down and refill?

NickD on Mon June 27, 2011 9:30 AM User is offline

Yeah, the blower motor switch, has to be on and be capable of supplying 12V to the compressor circuit. You need a circuit diagram, so do I, 50 years of electronic experience is not enough for me to guess what in the hell they are doing now, and next to impossible to trace over two miles of wires they are putting in cars today.

jgcox6 on Tue June 28, 2011 9:55 AM User is offline

If I have the blower motor switch on the a/c control unit selected to on....and the bad blower motor still in....are you saying that it will NOT supply the 12v to the compressor?

mk378 on Tue June 28, 2011 10:12 AM User is offline

Usually it would not have that effect. Simple mechanical controls are of two general designs. One has a separate contact on the fan switch to control A/C, so it's independent of the blower circuit other than that last ground. The other detects that the fan switch has grounded the resistor circuit to allow compressor to run. On that latter type, a bad resistor will cause problems with the compressor not running, but it doesn't need continuity through the fan motor. Of course there could be an obscure different design.

The most common reason for the compressor not to run would be refrigerant leaked out, so you should check the static pressure first and if that is the case, you have some time to check for leaks while waiting for the motor to come in.

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