Hi there,

I have looked on here but can find no answer to my question. My temp gauge has suddenly stopped working - is this a major cause for concern ? should I not use the car. Any advice would be much appreciated.

 

I've moved your question from General Tech Help to MKI / MKII S type 240 340 & Daimler forum because you really need advice from members here with the same model.

Jaguar don't have too good a reputation for reliable temperature gauges. Later models like mine don't even have one!

Graham

 

As I recall, there is a small thermistor screwed into the water rail on the inlet manifold somewhere. As the temperature rises the resistance reduces allowing more amps to flow. The temperature gauge is therefore an ammeter, but calibrated in degrees C. I think there is also a voltage device somewhere to provide a fixed reference voltage.

First check will be to make sure you have a voltage at the thermistor. Then you need to check the thermistor itself for resistance, easily done as it lets the current go to ground on the manifold. If the thing is open circuit, then you have a duff thermistor.

 

With out checking, there is also this quirky voltage regulator that fails as well.
It's located inside the car on the fold down electrical panel.

 

The MK2 gauges are calibrated to run at 10V, if the thermistor is open circuit you should have 10V at the terminal if negative ground and 0V if it is positive ground and open circuit. You can short the lead to ground and the gauge should show "boiling" , if not check input voltage to the guage and regulator as Jeff said.

You can get a solid state regulator from cool cat in the US to replace the old one for better accuracy.

 

also check for the Captain Obvious- loose/missing connections, poor grounding to the chassis.

https://www.google.com.au/imgres?img...act=mrc&uact=8

 

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