temp gauge zany! Ground or something

[paranoidjack]

Today I noticed my temperature gauge bouncing back and forth, quickly, from the "0" position to "actual" temperature. It didn't do it when it was cold, but once there was "room" in the gauge, it started bouncing around. I think it's probably a ground, but does anyone have any experience with this happening?

[black g50]

My tach sometimes does that at red lights.I was just told to replace cluster,but I would like to just know to why it does that.

[tfvesquire]

Happended to me on my 98 Q. It turned out to be gunk that got stuck to the end of the sending unit temp sensor inside the manifold. Unscrew the temp sensor and carefully clean off the tip and check for any accumulated trash floating at the bottom of the temp sender hole. Might also want to flush out your cooling system since you will mroe than likely have more trash flowing throughout your system. I cleaned mine and never had a problem again.

Hope that helps.

Ted

[elwesso]

Good advice there. A coolant flush is always a good idea if you haven't done it recently. Take a look at that sensor and most likely it should be obvious what's going on, the gauge sensor only has one wire.

[Skibane]

The temperature sensor produces a resistance that depends on coolant temperature.



If you substitute a 50 ohm resistor for the sensor, the gauge should read around mid-scale (since it is receiving approximately the same resistance as the sensor would be producing with the coolant at normal operating temperature).

If the gauge reading still bounces around while the resistor is substituting for the sensor, you know that the problem lies in the gauge - not in the sensor.

[paranoidjack]

Bang, bang, bang, great input guys. I'll check the sensor tomorrow, and I think I've gone about 20k on the new engine, so I'm due for a pre-summer flush.

Thanks.