The temp needle will NOT jump unless you have the early design coolant
level sensor control unit. I suggest replacing any early model "43" with
the improved model that came starting with later 1985 vanagons. The old
one causes confusion and heart trouble when it pegs the temp gauge
though the engine is not too hot, just because some air is in the main
tank.

The old one blinks the LED and pegs the temp needle when the coolant is
low.
The new one only blinks the LED while the temp needle continues to
indicate actual engine temp.
The old style will stop blinking as soon as the coolant level is ok but
the new version will not stop until the key has been turned off to reset
it.

New is 1 1/8" tall, part number starts with - 191
Old is 1 5/8" tall, part number starts with - 251

Both have a large "43" stamped in white numbers on the top.

The new style is also found on 1985 and newer Golf, Jetta, Quantum.

Either type works in all vehicles so either one could have been swapped
into any given year that has the level sensor in the coolant tank. You
can test which type you have easily.
With the engine running, remove the connector from the top of the
coolant tank level sensor, wait 10 seconds and look at the temp gauge.
If the LED blinks AND the needle pegs at the hot end, you have the old
style.

Mark

Damon Campbell wrote:
>
> As always, check grounds.  I would think that if the
> sensor went bad giving a false reading of no coolant,
> the needle would jump up as well.  Just a blinking LED
> would make me suspect a circuit independent of the
> sensor...  Especially if it has been intermittant.
>
> But definitely check the coolant level, anyway.
>
> -Damon
>
> --- Richard Brassaw <sendmeanemail@EARTHLINK.NET>
> wrote:
> > One of two things usually cause the blinking
> > light--other than your
> > engine overheating.  Either the sensor has gone bad
> > or there isn't
> > enough coolant in the system.
>
>