defender 300tdi overheating problems? help please

hi there i have owned my defender for the past 12 months had a few problems first time about 6 months ago it overheated causing the head gasket to fail had all this sorted out head skimmed and gasket done then had no problems for a few months i recently had timing belt pullies waterpump and p gasket done and radiator . the other day whilst driving the temp guage went into the red the heater was on this eventually came back down to normallity the half way mark then it would run fine for a few miles then back up to red mark i thought this was my thermostsat sticking so the other day i removed the thermostat and topped the coolent back up with no thermostat in i then went for a run out during the run the gauge didnt even move hardly from the cold marker and the heaters were running cool too i thought a new thermostat would be the case so i replaced the thermostat and topped back up with coolant i topped back up the system and then went for a run on the run the temp gauge started rising to half way mark as normal then the gauge did the same thing again went upto red marker heaters on again turned heat off and gauge dropped straight away also when i turned my lights off the guage dropped sometimes the marker goes into red and operating some controls makes a difference and other times operating the controlls has no effect on the gauge? baffled by all this please help

Sounds like an earth fault, confusing electrics usually are.

Thanks for the reply I hope it is a earth fault as I don't want the head going again any way of checking to see if it is a earth fault ?

If you want to keep an accurate check on the temp fit a capillary gauge with temp marked in degrees on it,only uses electricity to light the bulb.

I will have a look at capilary gauge ordered a replacement sensor for the time being, hope this works