False Temp Gauge Reading

[GeoffBooth]

Temp guage needle goes up when there is an electrical load added. For instance if you turn the headlights on, the temp needle rises. turn them off it falls just as fast.

[GeoffBooth]

I need to clarify this because I feel at least some of the over heating problem on this site could be due to this. Seems like the engine needs to be at operating temperature before it is noticeable. Regular driving with everything switch off seems fine. More current you pull the more it will react. Say your running with the lights on and it’s at normal then brake hard the gauge will go up two notches. Let you foot off and it will return to normal. Sometimes it acts exactly like you would expect if overheating. The other night it was playing up, I pulled on the drive, gauge at normal, turned on the head lights, up it went, turned them off and it returned to normal within a 3 seconds. It never goes into the red the system seems fine. Cool below the thermostat warmer above but in no way hot anywhere. None of this was happening until I replaced the thermostat due to no heat in the cold weather. I examined the old one and found it had been drilled through presumable to get better flow so some one messed with it before.
I would welcome any thoughts you may have on this problem.

[GeoffBooth]

The answer,
The 95/96 Rover has the old single pole sensor that earths through the engine block. This was changed on the 97 model I believe. The earth strap is on the pass side of the engine. Loops from the engine to the chassis, then to the battery. The fastener on the engine is small and probably inadequate for the job. In my case it had been rounded off, probably cross threaded and the cable was loose. I must have dislodged it while changing the thermostat. Just for a quick fix I ran another earth strap from the top of the engine to the battery earth until I get time to deal with the bad fastener.
Thanks Doug