This will not be a definitive answer, but may trigger some possible areas 
     to explore regarding temp sensors and the coolant system in general.
     
     I believe I may have read somewhere, maybe a Tech Bulletin, that it is 
     imperative that the coolant be 50/50 water/coolant(and phosphate free) so 
     as not to unbalance the ionic ratio? in the system, something to do with 
     conductivity?
     
     Also, it is important that the system be completely free of air, otherwise 
     there could be false indications of overheating.
     
     Air can be introduced by incomplete purging during a coolant change or top 
     off, or because of a slight leak in the system.  I read that some leaks in 
     the system are one way only,i.e., coolant doesn't leak out, however air can 
     be sucked in(pressure leak vs. vacuum leak in the system).
     
     Any comments?
     
     Pat S.

______________________________ Reply Separator _________________________________
Subject: Re:Coolant Temp Indications
Author:  Steve Hoge <steveh@emu.com> at INTERNET
Date:    11/15/95 10:36 PM

> The coolant temperature warning light sometimes flashes when the gauge 
> needle is showing max temp, and sometimes when the needle shows normal 
> temp.
     
I had the same problem this last weekend, just a few days after I had 
the dealer flush and fill my coolant (yeah, yeah, I know...) 
Temperature gauge showed normal, right amount of coolant in refill 
resevoir (couldn't see into the overflow tank), no visible leaking, 
tight V-belt, etc.  
     
I couldn't make heads or tails of the wiring diagram in Bentley - it 
looked like only a ground leading to the warning light part of the 
indicator, and the temperature sensor signal *only* (ie, no coolant 
level sensor) leading to the "gauge" part.
     
The interesting part is that the flashing indicator went away each time 
I turned off the engine and restarted it.  Is it possible that an 
intermittent sender signal gets "latched"?  Also, this problem seems to 
have disappeared now that I'm back down at sea level from 3000' to 7000' 
where it was happening.
     
Steve Hoge
'77 Loaf      (Da Rust Bucket)
'89 Syncro GL (Da Dust Bucket)