Oil temperature gauge - How to adjust the over-reading.

  • David Aiketgate
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  • David
  • David
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I know that some oil temperature gauges read really high from the factory and the accepted fix is to put in an in-line resistor to reduce the reading.
Apparently a 0.5w 15 ohm resistor was the one used.
The instructions below are from our friend Dieter's site:-

MGF MY1999 Oil Temperature Indication Failure

Affected cars: MGF Modelyear 99 (the first of the so called MY2000) approximate VIN range 511000 ... 52????, not official approved !!
Failure: Indicator for the oil temperature raises up to 170°C at high speed.
Reason: The dual Oil temperature Sensor does not relate to the specifications

Pull off the 13 position multiplug No. C160. This plug is located in the engine bay left of the main relay.
Cut the brown-blue wire at app. 60mm apart from the plug
Solder a resistor of 15 Ohm O,5Watt between this open connection and seal it with shrink tube.

Wanting to get a more accurate gauge rather than just reduce the reading, I bought a selection of resistors from 10 to 50 ohm at my local Maplins and prepared to experiment. They only stock 0.6w resistors but that difference is not important in this case.

I visited my friendly MOT garage and established that when the car gauge read 130 the oil was actually nearer 95.

So then it was a question of introducing the various resistors until the reading was correct. In the end it was 45ohms resistor that did the job.

Also I reasoned that it was substantially easier to introduce the resistors at the gauge end of the feed line rather than the quoted above position. So I made up a small adapter to go between the plug and the gauge. I soldered a male and female spade connector to each end of the resistor covered it with shrink tube and Robert's your father's brother.

Then it's just a case of popping out the centre vent and inserting my adapter into the line.
:broon: :woo2:


Last Edit:6 years 4 months ago by David Aiketgate
Last edit: 6 years 4 months ago by David Aiketgate.
The following user(s) said Thank You: Roverlike, cairnsys

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