At 07:40 PM 5/2/2014, Mister Tom wrote:
>Was not aware that the control circuit is inside the temp gauge.

What's inside the gauge is the blinking LED and a driver circuit that
turns it on for minimum 2-3 seconds a) when power is applied, and b)
any time the sender input is connected to ground by a low enough
resistance to indicate an overheat condition.

The coolant level control module (painted #43) applies a weak square
wave to one pin of the coolant level sender.  If that pin is shunted
to ground or any constant level by less than about 180 kilohms it
will swamp the square wave; and a few seconds later the module will
trigger and apply about 35 ohms to ground to the gauge sender input,
simulating overheat.  The original controllers did this continuously;
but the newer square ones only do it very briefly, often enough to
keep the blinker triggered but not enough to move the gauge needle to speak of.

>I can't make that repair happen, but I do have a spare temp gauge.

Last I knew Van Cafe had new gauges for something like $60.  Claim to
fit some particular year but should work fine in any panel with a
tachometer.  The gauge sender didn't change from year to year though
there were some slight variations in the gauge graphics, hardly
enough to notice.

>If that doesn't do the trick for me, is there a way to disable just the
>overtemp input to that circuit, and leave the coolant sensor working?

No, the blinker only reacts to overheat.  The coolant level detector
fakes an overheat to trigger the blinker, as I said above.

Yrs,
d