Smiths temp gauge calibration info

[94touring]

I've never had to calibrate a gauge before but this week was the week.  I went through 3 different temp senders on hand, one for sure is supposed to work with the gauge. All read very high, one pegging out.  I knew there was a way to adjust them but had never done it. So here's the intel if you need to do it yourself.  I took a crap gauge apart to learn the internals before I accidentally broke a nice brand new gauge. Back side of the gauge has 2 spots with little slots.  They don't screw with a flat head but rather slide on a pivot.  Both adjust the readings. Doesn't take much to adjust it.

[MPlayle]

So what was the step-by-step procedure?

[94touring]

Well find a very small flat head to pry against the tab shown above to then slide it around till the gauge reads N around 180-190. I believe it ended up being an inward movement that brought it from reading abnormally high to normal. With the car running you can adjust it and it will instantly change. 

[94touring]

Here's the same pics with arrows showing how it moves. The one with the singular arrow is showing it's already been moved full travel to the one side and can now only be moved in the direction of the arrow.

[cstudep]

Good info, I had no idea. I have bought every sender they make trying to get mine to read correctly, even replaced voltage regulator etc... never did get it to read anything other than H

[94touring]

The laser beam heat gun seemed to work best where I was shooting in the pic. Aiming at the aluminum radiator showed basically no heat, even though it was scalding hot to the touch. Seems to need a colored surface. This particular head has an adapter piece that the sender screws into. Shooting the sender itself read about 10 degrees cooler than the adapter in the head. Shooting the head just above the adapter to where the T-stat housing is read just a little higher than the adapter. So that seemed appropriate to me.
 The T-stat housing being silver in color didn't show enough heat to trust.  Shooting the head right to left in different areas you could really see temperature differences.  I always read that the side where the heater core valve is located ran hot and was more prone to overheat on that side. It showed about 20 degrees hotter just below the valve, till I turned on the heater core fan. It dropped very quickly to about match the sending unit side. 

[cstudep]

I found the same results when I was trying to get mine to work. The head temp around the thermostat area was about the same as a few other areas on the head right around there, and it gradually got warmer as you headed toward the heater valve. 20 degree difference seems about what I remember at the time.

The best I could get was the needle slightly off hot, so I just went with that, knowing if it went any higher I'd stop and check things with my temp gun. Now that I know I can adjust the gauge I will do that instead lol.

Thanks for sharing the knowledge!

[94touring]

Learning has occurred.

[MPlayle]

This post got me to doing a little web searching and I found these three manuals on Smiths gauges and tchometers.  The "Part 1" on gauges goes into detail on bench calibrating the gauges using those adjusters.