About 3 flight hours ago my OP gauge (Van's 2 1/4") started to red line then would return to normal for awhile before climbing again. I checked wiring and found no problem. Van's can no longer get those gauges but they still carry the sender which meant replacing that was my only option. I replaced it, flight tested it and got a high reading at first then it settled down and has been reading good since. I believe air in the lines had to be worked out of the system after replacing the sender but everything appears okay.
Dick DeCramer
Faribault, MN
N500DD RV6 17 years flying, All steam gauge since that is all we had!