I have a 2005 22' Launch with a Walter RV 26D V Drive and the low oil pressure warning light is staying on. I've checked the wiring and it's good. Hoses are good and the unit is filled properly. I pulled the filter, and it was clean, oil was clean and not black. I pulled the pressure switch and ran the engine in gear momentarily, and the unit pumped oil out of the hole, so pump appears to be good. I tested the switch with air pressure and it doesn't switch until 18 psi, is the switch bad? I thought it was supposed to switch at 8 psi?