Vehicle: 2000-’03 BMW 525I 2.5L

Symptom: Blower motor does not work, stays running all the time or does not have proper speed control.

Test & Fix:

1. The climate control blower motor is controlled by a final stage unit, which receives variable voltage from the climate control head.

2. Disconnect the final stage unit, which is located ­beneath the passenger side of the dash and installed near the firewall into the lower side of the heater box. Check for variable voltage coming from the climate control head when the fan setting is changed on the smallest gauge wire. If the voltage does not change as the fan speed is changed at the control head, a wiring or control head problem may exist.

3. There will be four heavy-gauge wires. One wire should have battery voltage at all times. Another wire should have a direct connection to chassis ground. The remaining heavy-gauge wires go directly to the blower motor. Supply them with power on one wire and ground on the other and the blower motor should operate.

4. If all of the above tests good, but the blower motor does not operate as requested, the final stage unit is defective and should be replaced.

Courtesy of Identifix.