WK-
Had a '93 S-10 pickup with a similar problem. In winter when things were moist, it would work about half the time, but when it dried in the summer heat, I would rarely get a reading. Investigating the fix, these modules come as complete factory pods. Not sure if you're a computer wiz, but I didn't feel comfortable cracking one.
Replacing the whole pod was the only solution. However, there are a lot of S-10 Chevy's or GMC's in the yards, so pulling one out of a wreck may be the best route. In addition you'll learn how best to putll the entire dash assembly so you can get at the pods. I'm not aware of a simple way of testing them for function when doing the salvage. You may be able to splice analogue gauges from earlier years, but I'll let others tell you if that is advisable.
Hope you live in a warm climate where you can get at the dash of wreck with compatible dash components.
