A chronic problem with a LOT of Volvos of your vintage, especially
140s and 164s is that the nuts on the back of the gauge seem to be a
different thread from the posts and the torque goes up when tightening
them before they are really tight against the conductor. On my 164, I had
had it for probably 20 years before I finally figured that out and got
the appropriate wrench and REALLY tightened it. Gas gauge worked right the
first time since I had had the car (1971). So if you pull the dash out
it would be good to look there and see if the thing REALLY is tight or the
nut just got hard to turn so they stopped tightening.
--
George Downs, The "original" Walrus3, Bartlesville, Oklahoma