cooling issue help!!!!!

i have a cooling issue which is a bit weird it seems to be going into the red but as soon as i stop the guage goes to normal sometimes. and when i put the heating on the temp gauge goes up off the red then heating off goes bk down a bit anyone with any help would be appreciated as im currently away in it at the mo and dont want to cook it. its an 1989 defender with a 300tdi in it.

Have you checked the coolant levels in the expansion tank and thermostat housing?
If the gauge is going into the red when you turn on the fan for the heater and then goes back to normal when you swith the fan off - it does sound like an electrical problem.

Remove the wire from the sender - run the engine - watch what happens on the gauge (might be a short to earth in the sender wire)

thermostat is fooked id imagine, more knowledgeable gentlemen will be along soon im sure.

Check the earths to your bulkhead and instrument panel.

I'd go with thermostat, check if you're getting heat through the blowers if not change the 'stat takes about 10 mins, no/little loss of coolant (make sure you fasten the jubilee clips properly when you've finished, found that out the hard way last week :doh

im gettin plenty of heat from heaters i will change the stat im also gettin a choke light on very weak though and i havent got an electric fan will check wires at the back of clocks to see if there ok.

Sounds like wiring, proberbly an earth issue which is sending the voltage through other circuits and bringing on various lights e.t.c.

Check all your earth points, well check all your connections for green corrosion and bad connections...

im not loosing any coolant or using any oil so think its goin to be electrical (what in a land rover never) so im goin to check the earths does anybody know where the earths may be to check thanks.

Behind the dash to the instruments might be a good place to start ...

I had the same problem, with lights, heater etc. on the temp gauge would rise. turned out to be a dodgy earth behind the gauge

think i mite of found the problem when i pull the handbrake on all the lights go brighter and the temp gauge goes spot on middle. and i think the main earth is attached to the transfer box so i am goin to try and bolt it to the chassis somwhere surely cant be a good earth on transfer box????.

yes there should be t/box to chassis ,body to chassis etc

im goin to add another earth to the body tomorrow thanks.

ive added another earth to the chassis and all is well (at least for now) so thanks everyone for all your help.

stick a strap from the engine to chassis too

i was thinking of doin that thanks for the advice.