Is my temp gauge accurate?

[Cooper]

I’m gonna give all the info I can, in hopes for the best feedback. 

 

The cars temp gauge didn’t work for the first year+, but a few months ago I added an extra ground to the fuel and temp gauge, and it worked after that, but the needle sits quite high. In the picture below, the needle is sitting maybe a needles width higher than it usually does, and I used the IR thermometer pointed at the water neck, and it measured about 200 degrees. 

The only thing to note about the cooling system that I am aware of, is it has an e21 radiator. 

So my question is, is the gauge reading correctly in that picture for 200 degrees? And if not, is there a way that I can get it to read lower? The car hasn’t overheated since I’ve had it, I’d just like to have a bit of a warning if it was going to, in the form being able to see the needle move some distance. 

Thank you. 

[dlacey]

You can also try to slacken and re-tighten the sender unit on the water distributor...corrosion in the threads can cause the gauge to read high...

[Cooper]

I’ve swapped the sender a couple times to see if it affected the reading. So if loosening and tightening it, would fix it, i think it would’ve done that by now. But I could try cleaning the threads with a brush, I’m just avoiding draining how ever much coolant is needed so that it doesn’t drip 

[02Les]

Not real sure how linear the gauge is, but halfway should be around 90C. At your 200F (93c) you're pretty close to that.

 

[Schon '02]

[Mike Self]

Schon '02 beat me to it--his post is a page from the CCA "Tech Tips" book, published in 1976, with a '79 addendum.  

 

mike

[Cooper]

So then it would appear that the gauge is a bit optimistic, but not by too much. 

My worry was that if it went in the red, would that even be an accurate reading, and something to worry about. So I guess that kinda answers that. Thanks to everyone, as always 

[Conserv]

Ignoring — and perhaps unaware of — the description in the Owner’s handbook, below, some owners panic when the temperature gauge reads above 3 o’clock. I do not. Most ‘02’s I’ve owned have operated, most of the time, between the red zone and 3 o’clock. Separately, most ‘02’s I’ve owned register a slightly higher temperature when electrical accessories, e.g., headlights, are turned on.

 

Regards,

 

Steve

 

Edited September 18, 2019 by Conserv

[coloincaalpine RIP 2021]

What I've found in addition to the above, is that, the actual "thumb nuts" that hold the temp and fuel gauges into the pod, have a propensity to also become corroded enough over the years to cause a poor connection to the pcb. I remove each gauge and clean up their mounting points thoroughly with fine sand paper,or whatever you choose. This is a very common problem often missed.

Good Luck,

dq