That brown is always ground. The voltage comes from the yellow/red wire
and the gauge. The gauge measures current flow through the wire and
sensor. As the sensor heats up it's resistance drops and more current
flows through it and the wire, so the needle moves higher on the gauge.

Mark

Dan Hall wrote:
> I"ve on the van since 1993.  In all that time, the temp gauge, after
> warming up would settle in around the center of the LED during highway
> driving.  Some thermostats would run a needle width warmer, some a
> needle with cooler.
> The current situation has the needle 2-3 needle widths past center of
> LED, almost to where the radiator fan would kick in.  I"ve never seen
> that before.
>
> Will endeavor to get a true temp reading.
>
> The coolant temp sender has two wires.  I red/yellow and a brown.   On
> page 97.92 fo Bentley the red/yellow goes to D29 connector on the
> fuse/relay panel.   The brown connects into the brown wire going to the
> license plate lite on current track 96, page 97.94 of the Bentley.
>
> Can someone tell me how the coolant temp sender operates?  Is it
> actually getting 12 volts off the license plate circuit and the
> red/yellow wire sends what voltage it gets through the sensor to the gauge?
> Or is brown wire always a ground?   And the the gauge is reading
> continuity to ground?
>
> Please forgive my ignorance on the operation of these electrical gizmos.
>
> Dan
>
>