Rorie said:

Old style gauge (white line to red line with no numbers)
Black sensor
300tdi out a disco

Even at idle, the gauge goes up to just below red. As soon as i drive the gauge goes as high as it can.
My understanding is the green sensor would make this issue worse (which it did when i tested)

Online the simple test is to put the signal cable to earth, then the gauge should go to red. It did! So this would suggest the sensor is bust.

New sensor, exact same reading (i swapped it when the engine was running).

So looks like the gauge is fault? Any way to test?

If replacing, are the OEM ones worth that money? Loads of cheap ones online, but its a simple bit of kit, right?

(oh, i should add, with a temp gun i can confirm the engine is only sitting about 40 degrees on idle and the thermostat isnt open yet, so must be a dodgy reading)

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mick 1986 said:

The sensor from the discovery isn’t compatible with the defender gauge. You need a defender sensor and adaptor to fit the discovery engine. I think Steve Parker website is where you need to look.

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tottot said:

Or for just a few more bucks fit an aftermarket capillary gauge that reads in numbers/degrees and is accurate.

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zeaphod said:

As above, fitting an aftermarket gauge saves a lot of faffing with getting the right sensor/gauge. A suitable Durite electric gauge is cheap enough, easy to fit and gives you a real idea of how hot the engine is.

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Litch said:

There is a direct replacement sensor to make the Defender gauge work with a Disco 300TDi but I don't know the part number (I have never done it) but I know it exists and hopefully someone can come up trumps. That way you keep the standard Defender gauge.
Although mine is Defender 300TDi I wanted to change all my gauges so went for the Durite electrical set-up, the supplied sender is a direct replacement for the Defender 300TDi (so you will need an alternative) but I am fairly certain that Durite sell one that fits (you need to establish the sender thread and speak to them).
The other option is to use a capillary gauge, I was going to do this on my Defender (and bought the necessary adaptor) but in the end decided I didn't like the fragile copper pipe and went electrical instead.

The only problem with changing just a single gauge is that the instruments don't match and anyway, in your case I don't think it is necessary.


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owas said:

AMR3321 is what I have fitted to my disco 300tdi in to early 110 and it's sits bang on half way (and then slightly over when I forgot to open the radiator muff!)

I have the one from Steve parkers too and that only sits at 1/4.

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