DeTomaso Mailing List: July 98, Message #240

The Mysterious Veglia Water Temp Gauge, 
                         or
How I THOUGHT my car was running hot.

I have an upgraded cooling system, so there is no reason
why it should be running hot.  But it was!  Or so I thought.
The car would warm up to 190-195, then rise up to 200-220
around town, and that's with new radiator, fans, temp-sending
unit, etc.  Frustrating!

Then......I decided to do the thermometer in the supply tank
comparison test.  There was a 30-35 degree differential,....the
gauge was reading WAY too high.  But why?

So Then...
- I take the gauge over to PI where Jerry Sackett and I check ohm
  reading comparisons with brand new gauges.  The readings are
  the same!
- I take the gauge home an re-hook it up the wires without
  installing it in the dash.  It reads almost PERFECT!   HUH?
- Oh well, so I re-install it in the dash and button it up.  THEN, it
  reads 35 degrees hotter AGAIN!  WHAT?
- I then dismount it from the dash again, hook up the wires, reads
  almost perfect.   Wait a minute!

What I found was that when I mounted the gauge in the dash, 
installed the U-shaped gauge bracket and tightened the thumb
nut, IF I over-tighten the thumb-nut (and it didn't take much),
the gauge reading would rise.  When I loosened it, would lower
down to the correct reading.

I cannot figure out why it does this, but it does. Was it creating
some sort of magnetic field?  Was the mounting stud on the 
gauge being pulled, distorting the gauge back?  But again, I 
wasn't tightening it that much!
 
So the only thing I tried as a fix was to heat shrink the U-shaped
bracket to keep it from making contact with the sides of the gauge,
and I put a phenolic washer between the thumb-nut and the bracket
to help isolate the two parts.  I snugged it down, put it together,
now it works great!   Now my temp stays around 180-185.

Anyone else experience this?

And those of you who also have high readings, CHECK THE GAUGE!
It's something to keep in mind, and if this helps anyone else,
please let me know.


Bryan Swartz    

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