Looks like you found the "confusing as hell" interpretation of my 25-year old notes. 40 ohms would put your gauge in the red, assuming my memory is correct that 1986 was the first year for the temp-faker compensation circuit. Now, according to my notes and recent tests, 40 ohms would result close to 9:45 or just past "3/4" as Volvo refers.

Up at the top of that note page is a test circuit using a 68 ohm resistor and variable voltage supply -- just to measure current vs needle deflection, because current is what is actually measured by the gauge.

Go to https://ozvolvo.org/archive/ Type 1985 or TP30808 into the search bar.

I don't know of any section 3 manual for 1985 describing the gauge calibration as was done in the older manuals for section 3 group 38 (instruments). I do know the temp sender and gauge sensitivity was not changed since those years even though the scale's legend changed in '81 as well as the reference regulator. (lookup TP11402) Page 60 is where the resistance numbers from Volvo appear.

Best download anything pertinent to your car while it exists on line.


--
Art Benstein near Baltimore

Time flies like an arrow. Fruit flies like a banana.