At 07:56 PM 11/18/2002, Jeff Palmer wrote:
>I thought I had read that an improper mixture could also cause the light to
>flash?

If the resistance between the sender pins is too high -- either no coolant,
or not enough impurities i.e. antifreeze in the coolant, or dirty pins --
the sender circuit will believe that there is no coolant and will trigger
the light.  It might well be that pure ethylene glycol would also not
conduct well enough to make the circuit work.

The circuit is quite sensitive -- as I recall something like 150 K-ohms is
enough to stop the light from flashing.  Electronically it works by
applying a very weak (high-impedance) square wave to one of the sender
pins, and grounding the other.  If there is coolant between the two pins,
it is sufficient to ground out the square wave [which causes the sender
circuit after a few seconds to start sending a much more powerful signal to
the gauge that triggers the blinker].

david

--
David Beierl - Providence RI USA -- http://pws.prserv.net/synergy/Vanagon/
'84 Westy "Dutiful Passage"
'85 GL "Poor Relation"