Mine comes on after a couple of minutes of driving and once lit stays on. Water and oil temp are fine and the fans all cut in and out as they should. There are no other lights that come on in conjunction with the stop light, if you remove the blue connector on the thermostat housing it goes out but the temp guage stops working, so it does point to a water related problem. I have checked all the earths and even run temporary earths from the battery neg to various points on the engine and chassis but it changes nothing.

Any other ideas? It was fine until a few days ago.

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Previous Peugeot - 2000(w)GTI-6, Me old China, Supercharged with working aircon!

would agree with stan given that unplugging the gauge/warning light sender solves it.

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need a part number? get on here - http://public.servicebox.peugeot.com

Bring on the Trumpets.

yes thy are different keyways, theyre also very different sensors too.

the blu sensor is a switch to earth on one pin (the stop light) and a variable resistance to earth on the other pin (the gauge).

the brown and green sensors are a variable resistance from one pin to the other, not to earth.

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need a part number? get on here - http://public.servicebox.peugeot.com

Bring on the Trumpets.

Replaced the blue sensor and problem sorted, thanks to all.

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Previous Peugeot - 2000(w)GTI-6, Me old China, Supercharged with working aircon!