That is way beyond my meager electrical ability..running a diagnostic like
that.  Though I am getting some base knowledge, having at least read
"Managing 12 volts" now and learned the difference between an open and short
circuit.

  Actually, I know the gauge works properly because I have overheated the
van in the past..with the gauge indicating so and checked with an infared
thermometer.  I think my thermostat may be misbehaving some..it was never
replaced, and I am in doubt now about the pressure tank cap and hose to the
overflow tank..  Though I suppose that little resistor could be acting up on
my cluster foil...
  I am going to check the big mechanical things first, but I appreciate you
taking the time to respond with the electrical diagnostic advice.
  Don Hanson

On Mon, Apr 19, 2010 at 5:23 PM, David Beierl <dbeierl@attglobal.net> wrote:

> At 12:18 PM 4/19/2010, Don Hanson wrote:
>
>>  My temp gauge usually reads on or just slightly above the second of the
>> bottom two marks...below that  LED.  Yesterday I was seeing the needle
>> just
>> above the bottom of those two lines, even when climbing to ~5000'...until
>> I
>>
>
> <snip>
>
>  move, over a 10-20min period from quite cool to where it normally has run
>> and maybe fall again...So my gauge is showing 'system running very
>> slightly
>> cooler than normal'
>>
>
> Don, the gauge is reading so low that it's hard to know what it means in
> terms of temperature difference.  Meters and gauges are much less accurate
> below about 1/3 of full scale.  I suspect the engine sender has different
> specs than the WBX sender.  To check the gauge itself and the wiring,
> disconnect the sender and substitute 265 (100/100/68, 5% half or quarter
> watt)  ohms to read right on that second line that shows the upper bound of
> the "transition zone" and 35 ohms (10/10/15) to read at the line beginning
> the overheat zone with the light blinking.  The gauge takes a couple minutes
> to stabilize, especially at the bottom.
>
> Yours,
> David
>