Before I run out and get a new cold-start valve...

Cody Forbes cody at
Fri Dec 14 15:51:34 PST 2007

Huw Powell wrote:
> Most likely culprit is the NTC sender on the coolant neck which tells
> the ECU the engine temperature.  It should be a few thousand ohms at
> freezing (remove and put in ice water), and under a hundred ohms near
> boiling.

Just recently I spent some time trying to graph the curve of this sensor, as 
well as the intake air temp sensor. Here's the graph I made: (temperature in degrees F 
across the bottom, thousands of ohms going vertically)

And heres the actual figures I measured for the coolant sensor:
100ohm = 203*F
260ohm = 140*F
400ohm = 120*F
470ohm = 110*F
687ohm = 92*F
784ohm = 85*F
1394ohm = 53*F
1728ohm = 43*F

It's highly likely that these figures will vary a little between multimeters 
and cars/sensors, but that will give you a decent chart to work from.

-Cody Forbes
'87 5ktq - Fast.
'87 5ktq QLCC'd plus some
'86 5ktqCD
'86 5k
'86 5k 

More information about the quattro mailing list