Crazy ongoing coolant temp sensore issue (G62)

[skragg]

Hello,

Audi A3 51 2.0FSI - I had the coomon issue - temp warning light and buzzer go off a few seconds after ignition, followed by the fans whirring up. A few miles down the road it would randomly go off and the temp guage would flick back to normal.

I did a VAG-COM and replaced the G62 with a new one bought online after lots of swearing (it's in a bloody awkward spot).

Problem was sorted for first few days, then the fault started appearing again! Exactly the same symptons, started with random bleeping and been gradually getting worse until it's now as bad as before I replaced the sensor.

VAG-COM gives the same error - voltage too low on G62.

Does anyone know how to fix this annoying bug?

[Crasher]

Was it the sensor on the head water housing or the one on the radiator outlet that you changed?

[skragg]

The head, on the main block, right hand side behind the battery. Green with 2 wires.

[Crasher]

Sounds like a wiring fault, could be difficult to find.

[NHN]

OP, which year is your car again?