88 5kcstq coolant warning problem (neither sensor!)

[auditude at cox.net]

I wrote: 
> 
> > My '88 5kcstq is flashing the coolant warning light.  Problem is,
> > when I disconnect both the expansion tank level sensor and
> > multi-function temp sensor, the warning doesn't go away.
> > 
> > My understanding is that those are the only two sensors that can
> > cause the warning light to come on, and that by disconnecting them
> > the system should default to no signal.  The expansion tank is closed
> > to ground when the tank is low, and the overheat signal is also
> > closed to ground.  So by unplugging both, I should not have the
> > flashing light.
> > 
> > What am I missing?
> 
> A shorted wire in one of those circuits?

Yeah, totally.  I'm not looking forward to searching for that, but I think that's what it's come down to.

I wonder if it would be easiest to do a continuity test on the warning light signal wires to see if they are grounded.  

Thanks Huw!

Ken