BMW E39 Webasto control unit and connector
The E39 Webasto only tries to start briefly and does not continue, what is wrong?
The Webasto has a lockout that engages after three failed start attempts. It is reset by disconnecting the battery negative cable for at least 10 seconds. This also resets the car's seat memory.
Why does the E39 Webasto not start after replacing the control unit?
A bus-controlled control unit needs a working bus connection from pin 2 of the connector, even if the heater is started with voltage. A voltage-controlled unit does not need the bus. On the 530d the unit was voltage-controlled from 9/98 to 3/99 and bus-controlled after that.
Can a single Webasto connector pin be replaced?
Individual pins are usually not replaced, because the hold of a single pin is not reliable. Replace the whole connector housing. Protect the connector from the wire side with silicone and clean the board of oxidation.
Is it worth repairing the E39 Webasto control unit or replacing the heater?
A new control unit is hard to get, so a faulty board is repaired or a repaired board is fitted instead. A board oxidised by moisture is a common fault. Removing the board often requires removing the whole heater, and the cover screws break easily.