:cry:
So, a few months back I installed an oil pressure sender and gauge from Autometer and it's been working great however, after a trip to the Azusa OHV area over the weekend and the deep (for my stock pickup) water crossings the gauge incorrectly reads zero oil pressure. I figure, since this seems to be a ground sensing unit, that it should naturally be waterproof?

I've crawled around underneath the truck and the sender wire is still connected and in good shape and I _definitely_ still have oil pressure. Is this one part not waterproof (or resistant)? What all should I look at to see if the sender is dead? If, in fact, the sender is not water resistant, what can I do to the next one I buy to ensure the next deep water crossing doesn't wipe it out too?

 

Get out your multi meter for this one....
If it is a single wire unit, you need to check it for resistance to ground at the guage (can be with the engine on or off). If you get infinite resistance then there is something wrong with the wiring or the sender (check the wiring at both ends for continuity, then check sender resistance itself by running a temp test wire again with the engine on or off). If you are getting proper resistance at the guage then the guage is faulty (or has a bad connection internally).

Your resistance values may look like either of these (Ohms should vary with engine RPM):

Zero pressure = 240 ohms,
1/2 gauge reading = 103 ohms,
full gauge pressure = 33 ohms.

0 psi 120 ohms
40 psi 51 ohms
80 psi 17 ohms.