P38A 2.5TD Strange temp gauge behaviour.

I know there's been loads of posts about temp gauges + over heating on the diesel engines but mine got a bit of an odd one, Its a 1995 2.5 auto and the temp gauge is going up into the red when the vehicle isn't actually overheating (for a change). What actually happens is the more electrical items you switch on wipers-lights etc the gauge go's higher up each time and puts the warning light on. As you switch them off one at a time the gauge will drop down in stages. Its only got the single wire sensor and I'm guessing I've got some kind of electrical issue but where do I start?

Brown single pin means you have no aircon.

The green one at front is the EDC temp sensor
brown is the gauge sender (your likely culprit) STC2253
You also have an IAT sensor in bottom of your inlet manifold at the front
Can swap them out for new if you take inlet manifold off. sensors are cheap plus manifold gaskets STC2203 x6 probably do it for a tenner.
Check the connectors/loom wiring/earths while you are in there and be extra careful to stay away from the wiring to injector no4 don’t snag it or even look at it

That's interesting, mines got aircon but also has the single wire plug and brown single pin sensor which I've changed today with no effect. I can't see any other sensors on the head apart from this one, don't mention the no4 injector as I had to change mine about 8 months ago and that wire is really easy to damage.

There are three sensors on the post 99 head the rear most is an overheat to bring on the electric fans. The middle and forward most tell the ecu and the Guage the Coolant temps. Not sure which way round but replace with correct colours. .
Check the earth below the fuse box,
Near the eas box, the drivers strut, behind the engines ecu, the earth from there down to the engine also..

There are two different type of gauge senders, brown and blue.
The brown is earthed through the body the blue is 2pin earthed through the loom

With AC I think you should have the blue 2pin sensor,
Unless yours has earth modified, or you have unoriginal engine.

Have a read through this
https://www.landyzone.co.uk/land-rover/m51-coolant-sensors.342180/

That's an interesting thread however still leaves me a bit confused as mine has the brown single pin sensor and only 1 pin/wire going to the plug. its at the front of the head and I didn't need to take the manifold off to change mine. It has had the engine changed at the dealer in 1998 but I can't see that making any difference. Even parts link 24 say's the single wire type is non aircon.

Read the bit about the earths.
Either can work it may have been adapted (or as stated earlier not working)

Run a temporary Earth see if it then works

Do you have 3 sensors on yours? Ie later head

I've got 2 sensors, 1 at the front just by the 1st glow plug which is the single pin brown and there's one about midway which I haven't touched. I did run a temporary earth yesterday but thinking about it I did engine to chassis rather than to body if that would make a difference?