BMW E28 temperature gauge not working
E28 temperature gauge is not working – where is the fault usually found?
Most often the fault is in the temperature sensor, its wiring or the C101 connector on the side of the fuse box. A poor connection in the connector is enough to stop the gauge working. Check these before suspecting the instrument cluster.
How do I check the E28 temperature sensor?
Measure the sensor's resistance with an ohmmeter between pins 1 and 4 of the diagnostic connector. The reading is from a few hundred to a few thousand ohms depending on how warm the engine is. If you get a reading, the wire and the sensor are connected; otherwise the break may be in the C101 connector.
The gauge does not work although the sensor and wiring are fine – what next?
The fault may be in the instrument cluster circuit board. Measure the resistance between cluster pin 12 and ground: about 1300 ohms means the wiring and sensor are fine. In that case check the circuit board's solder joints at the pin, because a cold solder joint can look intact but not conduct current. The cluster's capacitors can also fail.