I'm driving a US spec 1998 Audi A4 V6 Quattro, and just today my
coolant temperature gauge starting falling to C once it had reached
normal temp. Then it suddenly popped back to normal.
Sometimes it is normal after the car is started, then falls back to C.
The radiator is hot, the coolant level is good, the fan is working, so
I'm suspecting the sensor or a connection.
Any advice as to what to look for?
It is more than likely the sensor. You'll need to buy a new one as
the sensor and gauge are matched.
Check the sensor, wiring connections, wiring and gauge.
If you can get a second hand sensor from a car that is the same as
yours it may when installed show, a lower/higher reading, if the
reading is steady that it is the sensor that has malfunctioned.
If it is the sensor then you need to buy one. The sensor and gauge
Another sensor can work but the reading can be lower/higher.
If when you put in a known good sensor and you know the wiring is good
and the gauge raises and falls then it's the gauge that's
If you know the sensor and gauge are good then it's the wiring that is
Air in the coolant and a collapsed coolant pipe, sticking thermostat
may also cause the gauge to fluctuate.
I do not know about your car.
Mine is a 1996 A6 1984 cc 4 cly engine which has 2 sensors one for the
gauge and one for the computer.
Getting to to the gauge is a long job.
I had a 1986 4000CS quattro where the coolant temperature rose to normal,
and then fell down towards C. If I slowed down, or followed someone
closely, the temperature rose. It then fell again if I was in clear air.
Solution was a coolant flush and refill.
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