Nasty Temp Gauge reading low

January 01, 2024, 03:48:35 PM

Hi everyone ! Any suggestions regarding a annoying fault I'm fighting with at the moment ! MK2 8V 1991.... Temp gauge is reading low.... so far I have changed both temp sensors with VW items and a new thermostat but still it reads low... I have bridged the sensor and the gauge rises to the far right .... scratching my head with this one !!

Re: Nasty Temp Gauge reading low

Reply #1 – January 05, 2024, 11:41:30 AM

Have you checked the thermostat fitted is working correctly? It's possible to get a duff one, you should always test them in a jug of boiling water before fitting.

To test, start the car and let it idle. Hold the bottom radiator hose and check it's cold. Keep checking, it will stay cold until the engine gets up to temp and the thermostat opens. The hose will then get hot really quickly and it won't be possible to continue holding it.

If the bottom hose warms up gradually then the thermostat is faulty.

If that checks out, then I would ask if your heater works properly. Has a new matrix ever been fitted, and is the heater bypass valve still fitted? Issues here could be stopping the water from flowing around the system properly.

Only if you're sure these elements are all working then I would turn to the gauge and/or a potential electrical fault. Are the wires in the engine bay in good condition?