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BMW Inoperative A/C, Heater Blower Motor – E28, E24, E21, E12

March 22, 2011

The blower fan ONLY works when the A/C switch is on. Let us assume that the control valve is set to the cool setting and I just want fresh air without turning on the A/C switch, don’t you think the blower fan should work under the cool setting? So now I’m confused because the blower should work whether the setting is set to cool or hot position without the A/C switch being turned on. It seems like the A/C switch is controlling both setting.

Your 88 535is has two fans for the heat and A/C. One fan for the heater and one fan for the A/C.  This is applicable to the E21 chassis (3-series through 83), E12 chassis (5-series through 81), E28 chassis (5-series 82-88), E24 chassis (6-series through 89).

It sounds like the heater fan is not functioning and when you turn on the A/C, then the A/C fan does come on. The heater fan is located at the top of the cowl area, between the wiper arms. It is accessible through a removable panel in the engine compartment … at the top of the firewall (this is detailed in the Bentley repair manual). You may want to get in there and test the motor to be sure that it is the failed part (as opposed to something else causing the motor to not get power). You can test the motor by applying power right to the motor’s terminals with jumper wires. You will also need to determine which motor you have …. Bosch/Behr or Sofica. The A/C blower is located down in the center of the console, forward of the black grilled area.

Bentley Repair Manual:


Heater Blower Motor – Behr/Bosch:


Heater Blower Motor – Sofica:


Air Conditioning Blower Motor:


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