[s-cars] Re: Heater Control Temp vs Temp Gauge

[J. Khang]

 --- Bob Rossato <bob.rossato at att.net> wrote: > > What
I observed yesterday was that the climate
> > controller reported the coolant temperature to be
> 50C
> > after a restart (the car had been driven a short
> > distance and also idled while the coolant was
> topped
> > up) about 15 minutes after I completed the
> thermostat
> > change. It stayed at 50C for a couple of miles
> before
> > proceeding towards 87C.
> >
>
> That appears to be normal.  Mine did the same thing
> (holding at 50C).  What
> was odd was that I decided to check it first thing
> in the morning with
> ignition on but engine not running and the
> temperature would continually
> increase.  When I accessed channel 51 it was around
> 10C and I watched it
> increase to 37C with the engine still off before I
> went ahead and started it
> up.  At that point it continued at the same rate and
> then held at 50C.
> While it was rising with the engine off the fan
> would react to different
> temp points.  The only thing I can figure is that
> the sensor has a
> pre-heater built in like the O2 sensor and it stops
> at 50C.  Why I don't
> know and haven't checked it see how many wires are
> going to it.  Just
> another of those funky things.

Hmmm, that would be why the climate controller always
displays a temperature higher than ambient whenever I
start the car in the evening after work.

The increase is probably due to resistive heating. The
sensor is a resistor and it is read by applying a
voltage across it. That would start heating it up.

Jonathan
'96 S6

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