hi, my temp gauge doesn't work. i replaced the sensor but still doesn't work.
im trying to get my head around how it works.
i know the sensors resistance changes with temp and moves the gauge, but i thought u would need two wires one 12v and the other going to the gauge.
how does it work with just one wire?
should this wire have 12v?

any help would be appreciated
cheers ryan

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1971 mk2 police cooper s
1988 rover mayfair modified!!

Regulated +ve voltage -> gauge -> sensor -> ground

Only needs one wire as it is the ground side of the gauge (grounds by screwing into the engine).

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Too many cars, and too little time.

With ignition on, power goes from 12v to the voltage stabiliser at the back of the speedo, then from the other side of the stabiliser to the Temp guage. (Also to the Fuel Gauge). The other wire from the temp gauge goes to the sender, which earths through the engine block to give a reading.

If you use lots of teflon tape on the sender it will prevent it working.

Dioes the fuel guage work and is it relatively accurate? If so, the voltage stabiliser (small squarish tin can behind the speedo) is working.

I'd check the wiring between the voltage stabiliser and the guage, then the wiring from the gauge to the sender.

It's highly unlikely to be the gauge itself.

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Brett Nicholson
Greendale (near Ballan) VIC.
1971 Morris Mini Moke
1966 Austin Mini
1965 Morris Mini Traveller
1973 LR Series 3 88
2007 LR Freelander 2

so the sensor prong acts as a good or bad ground?
so the wire should have 12v then?

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1971 mk2 police cooper s
1988 rover mayfair modified!!

this is on a 1988 rover mini, so the back of the instrument cluster has that plastic film with circuits on it

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1971 mk2 police cooper s
1988 rover mayfair modified!!

Quick test.

Turn the ignition ON. Disconnect the wire from the sender (sendsor) and short it to Earth. The Gauge should read HOT. Don't leave it this way longer than is needed.

If that is OK, the the sender (even if new) is crook or bad earth though it.

If it does not, the the Gauge or wiring has a fault.

If I recall, the Rover Mini's with the sieko instruments do not use a voltage stabilser.

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thanks for all your help guys.
it was a bad ground that was the problem!

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1971 mk2 police cooper s
1988 rover mayfair modified!!