My 96 disco with 169000 miles it's overheating, and I can't find why, no leaks , all the fans work, and it only overheats when I turn the lights and the ac on??? I took out the radiator and flushed it, the head gasket was replaced less that 1000 miles ago, oil level is correct, so is coolant level , when the temperature goes up if I turn off the head lights and ac the temperature goes down instantly , and if I turn them back on it goes right up , what it makes me think it might be the gauge sensor or an electrical problems, it can be 100 deg outside and I being stuck on traffic as long as i keep the light off and the ac off the temp gauge doesn't move , I check the belt tension and the way is routed and it seems to be correct to , please help , I don;t know what to do , and i line in Florida i need the ac!!!!

 

Have you rebled the coolant system to make sure there is no air in the system?
Have you actually seen the electric fan on either with the a/c on and or while driving in town?
Have you verified that the hub for your main fan is engaging as it should?

 

I have checked that the fan is on with the ac and while driving , and the fan seems to be fine, how do get the coolant rebled???

 

https://landroverforums.com/forum/sh...ad.php?t=23072
this link is for the d2's i'm not sure if it's the same for the 96's or not ... (mike is it the same, or at least close?)

 

I have this same issue in my rover. The more electricity you use the "hotter" the vehicle gets. Hook an obd scanner up to it, should stay between 190 and 195F if it gets hotter than 210F you have a problem. I could not figure this one out for the life of me either! Apparently it is a loose ground wire somewhere that causes this....Normally this is a range rover problem, but I suppose discoveries can get them too.

 

I'd look at the possibility of your truck not actually being hot, but rather that the gauge is glitching. See what the OBD says while running, and/or try an aftermarket mechanical temperature gauge.

The Temp gauges on these trucks are kind of a joke regardless. Mine comes up to the dead-center of "normal" and never moves, it reads this way from 160 degrees all the way to 220 degrees! That's an awful lot of variation for the needle not to move. For those wondering about how I gathered the data on the temp gauge and its reluctance to fluctuate appropriately, I've driven with the OBD scanner hooked up to monitor actual operating temps at idle, on the highway, in town, under load, etc.

 

I have an infrared thermometer and there is no variation on the temperature , so it's definitely the gauge , any suggestions on how to fix it????

 

Mechanical gauge on a "T" fitting (Im not 100% sure if it will fit but that is what we did on the race car).

 

There is a way to bypass it, so it does not go through any other grounds. That is how it is fixed on the range rover at least. I don't know about discovery.