I had the dread flashing red light recently (frequent but intermittant -
usually came on after running 5 minutes or so.    Running fresh 50-50
mixture of Prestone orange,  5 year (?), no-phosphate antifreeze).   I
first cleaned up the sensor connector and reconnected it.  No luck.   I
then took the sensor out of the coolant tank and inspected it.   The sensor
pins looked very very clean (they look like some sort of stainless.)    As
an experiment though, I thoroughly sanded the pins with 400 grit carbide
sandpaper.    Reinstalled them and have not had any problems since.    So
it's possible that I removed some sort of invisible oxide or film, or that
the sanding increased the effective surface area of the pins a little and
made the (maybe defective) sensor circuit) happier.

It's easy to try it.   Your mileage may vary...

Dave
90 Westy

At 09:06 PM 9/8/02 -0500, John Rodgers wrote:
>There are many things that have to be "Right" on this cooling system. If
>any one
>of them are "Wrong" the light will come on. There can be no air in the system.
>And the coolant MUST be a 50/50 mix - antifreeze and water (best is distilled
>water)
>
>If the cooling system overheats, the light comes on. If the coolant level
>is to
>low, the light comes on. If the anti-freeze mix is incorrect - the light comes
>on. If there is air in the system the light will come on.
>
>If all else seems ok, check you coolant mix ratio. Remember - 50/50. No
>more, no
>less.
>
>If that is ok, park on a STEEP downhill grade, facing downhill. With the
>engine
>warm and the pressure cap off, run it at 2500-3000 rpm to really circulate the
>coolant. This should burp the cooling system. Top off as necessary with
>the 50/50
>coolant. Replace the expansion tank pressure cap. Give it a road test.
>
>Beyond all that, you probably have an an electrical problem somewhere.
>
>Good luck.
>
>John Rodgers
>88 GL Driver
>
>Michael Wagner wrote:
>
> > Folks -
> >
> > Need some suggestions.  The dreaded flashing red coolant light has come
> on in
> > my '85.  The van isn't loosing any coolant, the main coolant bottle and
> > overflow is full, everything appears to be fine.  I've replaced the sending
> > unit that is on the main coolant bottle, so that isn't the
> problem.  Nothing
> > else is obvious to me, so I need to start digging into the 'less obvious'.
> > Any suggestions are much appreciated.  I know I'm not in any danger
> from this
> > condition right now, but in the even that the main bottle ever does loose
> > coolant, I'd like to be aware of it.  And besides, the flashing red
> light is
> > just plain annoying.
> >
> > Thanks for your help.
> >
> > Mike W.