2002 Oil Pressure Gauge

[350Driver]

Hey folks.  I've got a 2002 with a Merc 305 I/O and have been trying to track down the reason my oil pressure gauge pegs out on the high side with the ignition on.  First I tried a new "to me" gauge.  Same results.   Next came a new sending unit.  Still pegs full high.  When I disconnect the wire from the sending unit, the gauge drops to zero.  Any idea what's happening here?  

 

[cwag911]

With the gauge dropping to zero when you're disconnecting the wire sure sounds like the sending unit is bad and don't be fooled since it's new. They can be new and bad. Are you sure you got the correct sending unit? If it's one for a warning light and not a gauge, it will be grounded to turn a light on. Check it with an ohm meter with it off the motor.

 

[350Driver]

Turned out to be a bad gauge.  I suspected the sending unit as well.  


Now on to the trim gauge gauge that is now doing the same thing.