Pretty darn sure that that Coolant Level Probe in the Expansion Tank

is nothing more sophisticated than a simple Switch > When the Probes are

Submerged > Circuit Closed,, When Coolant Level drops below Probes the

Circuit Opens ~ Any Break in the Circuit will cause the Light to come on ~

There are some Electronic Components within the Circuit that can cause the

light to have some odd behaviors @ times ~ I have seen, in several different

Vanagons, a condition where if the Igni’Key was turned to Start in a normal

way (1 continuous move from Off to On to Start) the Light would Stay Lit

but if the Igni’Key was turned to On & left in that position for 10-15 Sec’s

before turning to Start then the Light would go Off & act normally ~

I suspect that D Beierl or Dennis H or others may have an explanation for

that condition ~

> On 16 Sep , 2022, at 9:33 AM, Ed <email99@NC.RR.COM> wrote:
> 
> I believe the coolant light circuit measures resistance between the two pins
> of the sensor in the plastic tank.  If the resistance is out of range then
> the light will come on.  If the coolant is low or sloshes away from the
> sensor pins then the light will come on.  If the coolant has too much
> antifreeze then the resistance between the pins will be out of spec and the
> light will come on.  If the pins are dirty or corroded then they might read
> incorrect resistance.  There could also be a fault in the wiring for the
> light that could cause the light to come on.  I don't know how to test the
> sensor.
> 
> That all I have.
> 
> 
> 
> On Fri, 16 Sep 2022 05:57:37 -0700, David McNeely <davmcneely40@GMAIL.COM>
> wrote:
> 
>> Doesn't the coolant light indicate the level of coolant, not the
>> temperature?  I have actually had it come on when I hit a rough spot in the
>> road, back some years ago.  Bouncy, bouncy, and the light blinked on and
>> off.
>> 
>> On Fri, Sep 16, 2022 at 5:16 AM Ed McLean <email99@nc.rr.com> wrote:
>> 
>>> The original note was a short question asking why the coolant light would
>>> turn
>>> on and off at random times for no apparent reason while the temperature
>>> gauge
>>> remained in the normal range.
>>>