Rick's Free Auto Repair Advice

BMW fan doesn’t work

My BMW fan doesn’t work

If you own a 2000-’03 BMW 525I you may have already experienced a BMW fan doesn’t work condition. If yours has been running fine, consider yourself lucky and start saving money—it’s gonna fail. The motor itself is controlled by a component called the “final stage unit.” It’s located under the dash on the passenger side of the vehicle. The climate control head sends a variable voltage down to the final stage unit, telling the speed to run at. So start your diagnostics by checking voltage on the blue/red wire. Vary the fan speed on the controller head and look for changed voltage on that wire. If it doesn’t change, the control head is bad (you can get those rebuilt).
Next, check for battery power at the red/blue wire and ground at the brown wire. If that checks out, disconnect the connector from the final stage unit and jumper power and ground to the red/green and black/green. If the blower doesn’t kick in, swap the hot and ground and try again. If it still doesn’t run, the blower motor itself is bad. If the motor runs, the final stage unit is bad.

© 2012 Rick Muscoplat

Posted on by Rick Muscoplat

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