Water Temp light flashing intermitently - Mk2

Hi,

Had this problem when I brought the car some 18mths and 2k miles back.

When driving, mainly when wet and going round corners, the water temp light will start flashing (red) and the stop after a little while. It would do this when the engine is hot or cold. As the fan is cutting in ok and the temp is just on the hot side of middle, I figured this was not an issue and over time, it stopped happening.

Unfortunatly - it's back!

I think it my be a corroded earth somewhere which is shorting when wet - but I don't have a clue where to start looking!

BTW - she's a 86/D C 1.0lt breadvan with 20k miles covered... if that helps!

Thxs - M