Temp gauge how does it work?

Rorie said:

300tdi. As soon as I start the engine the gauge creeps up. Within a few miles it’s redlining. I know it’s false reading as the engine is still not hot, electric fan isn’t on etc.

This happened last month when I put a new 300tdi in out a disco, turned out it was the wrong sensor for the gauge. Changed it over, all worked well.

Only change here is I drilled out the green filter for the light so I could put in an LED. I was really careful to let the drill cuttings drop out etc. I had no doubt that I never touched any of the inners.

So how does the gauge wrk? Could I have damaged something? Earth fault? If I pull the cable from the sensor the gauge drops, so seems to be wired correctly...

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Dippypud said:

Sender from your old engine is correct for the gauge you have fitted to the vehicle ...

This one isn't ...

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Rorie said:

Nope. The old one showed hotter than it was. This one showed the correct temp. Nothing has changed other than me taking the guage out, drilling the back and putting back in.

I assumed it was the wiring, but all looks right (took photos before I pulled the cables out)

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