I wonder how much can be put down to variables such as sending units and the guage itself. Our 85 wagon now runs normally right between the 80 and 100 marks. Sometimes if leaning into it, the guage will climb to a couple needle widths below the 100 mark.

If I put on the heater it drops the guage down quickly to a needles width above the 80 mark. It stays there with the heater on for a couple minutes and then goes back to normal right in the middle. I consider that 90C obviously....but have shot the head with an infrared laser temp gun and the most I have seen with the engine running at idle is 74.5C and that is at the base of each injector. At that temp. gun reading.... the dash guage is saying it is 90. Which guage is correct ...the temp. gun or the dash guage?.... Don't know.... I always thought that these VDO guages had a good reputation for being accurate and maybe it is??. I guess I could try to find something to compare it to as a known accurate temp. This 85 wagon has two sending units in the head....I think the front one is for the guage and the back one is for?? My other diesel 617's only have one sending unit in the head.

We wired a toggle switch into the auxiliary fan and have removed the A/C condenser. That auxiliary fan switch was a waste of time according to my dash guage as it does nothing to lower temperatures when the aux fan is running.

I wonder if you have one of these temp. guns to check your temperature out for a comparison? They come in handy and are always going on sale for like $30...Princess auto. I think you guys to the south have a place called Harbour freight which sounds like an equivilent type store.Could be a cheap general diagnostic tool.