It’s fall and starting to get colder so you really want your car’s heat to work. Follow this Real Fix to see how the malfunctioning heater in this BMW 528i was diagnosed and repaired.
Vehicle
1997 BMW 528i 2.8
Title
Heater inoperative, repaired HVAC blower motor resistor wiring harness.
Complaint
The customer states the heater is inoperative.
Cause
Confirmed the customer’s complaint and found the heater was inoperative. Connected a scan tool to monitor live data and found the engine control module command for air conditioning (A/C) compressor operation was present and the specified A/C operating pressures were within specifications. Accessed the heating ventilation air conditioning (HVAC) system control module with the scan tool and found the HVAC blower motor did not respond when commanded on. Accessed the HVAC blower motor connector, backprobed the connector with a multimeter to measure the 12 Volt supply and less than 100mv ground at the connector and found the supply voltage was not present. Disconnected the connector for the HVAC blower motor, inspected the connector, terminals and wiring harness and found no faults. Reconnected the HVAC blower motor and traced the wiring harness to the HVAC blower motor resistor wiring harness connector. Used the multi-meter to backprobe the HVAC blower motor resistor wiring harness connector and found 12 Volts was present at pin 1 the HVAC module input and pin 2 the HVAC blower motor supply. Wiggled the wiring harness and found the HVAC blower motor operated. Split the insulation open to the wiring harness at the HVAC blower motor resistor and found the wiring harness was damaged.
Correction
Repaired the HVAC blower motor resistor wiring harness and verified the vehicle operated properly. The customer’s concern did not return.