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water temp sensor - gauge

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I have in my defender 90 300Tdi a Td5 dash (incl gauges) but the water temp gauge doesn't work right. So the sensor in the engine block isn't right I guess. Because when the engine is on the right temp, the temp gauge stands complete in the red zone.

Does any one knows which water temp sensor I need to have to correct temperature on my gauge?

For wiring I use the loom from a defender ROW spec 300Tdi.


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yep green top sender is what you need

Code~: AMR1425

Also check you have good contuinuity on the sender cable as this screwed me over, then if you have to replace make sure you replace properly so it still goes through the speedo, i shortcutted and went straight to the guage then somebody pointed out that was why my guage was reading too hot still lol (thick moment)


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If you have a ROW-spec wiring loom (behind the dash) then the signal should be passed through the speedo head before connecting to the gauge, so that should be OK. Sender is AMR1425 as above, get a genuine one as the pattern ones are not as good.

The gauge works on resistance, no resistance (ie. short to ground) would be full deflection on the gauge, or full hot if you will. Full resistance (open circuit) means the gauge won't move at all, so full cold. The sender decreases in resistance as water temperature increases. So if you gauge is reading too hot, then there is too much resistance, this could be due to either having the wrong sender (check to see if there's a green plastic ring on it like this) or some extra resistance in the wiring loom (dodgy connection etc.).

Hope that helps.

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  • 5 years later...

Hi Guys

I know that one very old - sorry for that - but can not sort it out

300 Tdi in RRC from 1983 dashboard

Green water temp sender - new

300 Tdi with no AC - there was one but taken off currently

Second termostat already placed in and ...

Gauge goes to red zone :///

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