I don't understand why anyone would replace a coolant level sensor, unless
it was broken and leaking.  The prongs can simply be cleaned, shined with
sandpaper if you like.
  Are you using a particularly corrosive coolant mixture?  Distilled water
or water from a dehumidifier is a good thing.

Larry A.

On Thu, May 16, 2019 at 3:28 PM email99@nc.rr.com <email99@nc.rr.com> wrote:

> I have, once again, replaced the 251 919 372 Coolant Level Sensor to fix
> the blinking red light in the Coolant Temperature Gauge in my '86
> Westy.  It is most annoying that this excessively high priced sensor has
> to be replaced on a regular basis.  Certainly VW could have figured a
> way to measure coolant level rather than with this sensor.  I have had
> to replace this sensor regularly about every 10 years and the cost has
> now reached the exorbitant level of $1.80.  The list price from one
> vendor is actually $42.44.
>
> When replacing the sensor this time I made an observation that might
> help us all avoid this expensive repair.  When the old sensor was
> removed I noticed one of the sensing pins was bright and clean while the
> other was black and rough.  Since the level gauge measures resistance
> between the submerged pins there must be a constant small current
> passing through the coolant between the pins.  This constant current may
> be removing ions from one pin and depositing them on the other, thus
> changing the electrical activity of the surface of both.  After 10 years
> the difference might be enough to fool the electronic circuitry and
> cause a false positive blinking light.
>
> Has anyone else noticed this difference in appearance of the used sensor
> pins?
>
> I suggest that the electrical connections to the sensor be reversed on a
> regular basis to keep the pins in equal, clean condition.  The
> electrical plug is not keyed to fit in the sensor so this is an easy
> thing to do by rotating it 180 degrees.  Doing this often will not be
> detrimental so maybe at each oil change would be easy to remember.  Or
> maybe just do it once now and forget about it.
>
> Just my Vanagon experience today.
>
> Ed
>