my temp gauge is not working but the light keeps flashing. I put in a different cluster and it still doesnt work.
Take the wire off the sensor and hold it to ground (anything metal on the engine) and if the gauge goes all the way up; sensor is bad. If the gauge doesn't move, you have the wrong sensor or something is up with the wiring.
The coolant will drains just enough by itself once you remove the sensor Or move faster.
Never a bad idea to drain and flush the coolant if it hasn't been done in a while
MK2 Partout / Cleanout: http://forums.vwvortex.com/showthrea...8-GTI-of-sorts
The black plug/sensor runs the temp gauge in you cluster, which you fixed and works now…. the blue plug/senor sends a message to your ECU, which will then trip the coolant light on if something is wrong. And yes they are different sensors so make sure you get the right part #. Either the blue sensor is bad and or like Greg_J said, the sensor in the back of your coolant bottle could be bad. Unplug it and see if it’s got any corrosion on it, if so clean it off and plug it back in. But Like I said before, be sure to check the wires into the plugs/sensors, if they are broken and not completing the circuit it will send a false signal.
I've had good luck when replacing these sensors to uncap the coolant reservoir and then cap it again to release back pressure. When you recap it, it creates a vacuum so that when you take the sensor out, it only drains a little as the pressure is holding the coolant in the hoses...
I put a blue sensor where the black one was supposed to be and plugged it in. Exploded! Twice!! (I did it again because I thought the problem was something else). So yeah... don't do that.