<VV> CHT (Cylinder Head Temperature for the acronym impaired) gauge

[Padgett]

>  Datsun/Bosch EFI that uses a VW head  temperature sender!  I
>went out and measured the resistance of the Bosch  sending unit at ambient 
>(80F)
>and it was 2400 ohms.

Just ran some tests on the Corsa dash gauge I am restoring and got the 
following:
Temperature                             My gauge                Rishel 
chart (online)
200F (first mark)                       1000 ohms               1000 ohms
300F (second mark)                       200 ohms                 300 ohms
450F (between center and next)   100 ohms                 200 ohms

So there is quite a variation but then GM gauges seem to be more 
"indicators of change" than precise devices. Am sorting out the garage to 
free up a bay right now and could not set my hand of a 1k pot which would 
have been much easier so was using discrete components. Will create a chart 
once I do but thought would be handy to compare to the VW thermistor.

Fuel gauge uses a similar circuit just reversed and with much lower values. 
AC developed this mechanism many many years ago.

Padgett