David Katsuki wrote:
>
> Where is there a coolant pressure sensor in the system?   I've never seen
> one and don't recall
> any reference to one in the manual.

as I mentioned in another part of this thread, AFAIK the coolant pressure is
determined by the temperature sensor - if the pressure is high the computer assumes
that the temperature is high. That is what the techs at VWOA HQ told me when I
stopped by their "house" in 1985 in the middle of my
round-the-country-bleeding-pressure trip. They may have been full of crap, but I was
an early victim of the coolant corrosion problem.

There seem to be 3 different sensors related to coolant in the Bentley I have
(1980-1984) - the Temp gauge Sender located on the thermostat block and Coolant
level warning switch shown on 19.8 and wiring diagram 97.31 both send voltages to
the gauge/warning light ONLY.

Temperature Sensor II is also located on the thermostat block and is shown on page
19.8 and checking info on page 24.32 and wiring diagram 97.30 - only sends voltage
to the Fuel control unit (and probably to the unit marked TRNSTR IGN CNTRL Unit -
[translates as Transitional Ignition Control, I guess, and is not the Hall Control
or Idle Stabilizer unless the units are combined somehow ] which seems to exist on
the wiring diagram but I cannot find mentioned anywhere else in the Bentley - and
was the cause of another mysterious bug in my bus, BTW...)

but anyway, from the Bentley I cannot tell how the Temperature Sensor II actually
works (thermocouple or pressure) - anybody know?

>
> Is it actually the level sensor in the pressure tank?  That doesn't seem to
> be connected to the computer in any way,
> and mine ('90) flashes randomly without impacting performance.   Maybe a
> bad temp sensor?

Pressure build up often  led to a large air bubble in my coolant tank during the
1985 problem - that would have caused the Coolant level warning switch to peg the
gauge and light the LED.

Dave Richoux  83.5 Westy