autocheck coolant warning

Kneale Brownson kneale at
Sun May 7 16:25:08 EDT 2006

Try jumpering the contacts in the reservoir connector to see whether the
light goes out.  I think this one operates like the brake pad warning where
there is no signal until you break continuity (by the float lowering)
except your sensor in the tank is failing.

At 03:47 PM 5/7/2006 -0400, George Selby wrote:
>The coolant either low or overheat warning has started coming on in my 90 
>Audi 200's autocheck system.  It's not low on coolant, and it's not 
>overheating.  I have tried the three different multi temp switches (2 three 
>prong, and one 4 prong) I have, and they all do the same thing.  When I 
>first start the car, it won't come on, but within 1-5 miles it will start 
>flashing.  Sometimes it will go out while driving, but then comes back on.
>I have tried unplugging the multi temp sensor, and the coolant low sensor in 
>the overflow tank (separatly, and at the same time.)  I have also just 
>unplugged the blue/yellow wire from the multi temp switch - this results in 
>an immediate flashing of the warning.  The only thing I have noticed makes a 
>difference is when you unplug the multi temp switch, then plug it back in 
>the light will go off a couple to 30 seconds, then start flashing again.
>How does this system work?  I figured unplugging both sensors would make it 
>stop, but unplugging the coolant tank switch seems to have no effect, and 
>unplugging the multi temp switch makes the light come on instantly.  Are 
>there any other sensors associated with this warning system?
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