Problem with Oil presurre indicator

[defrkm20j]

Hi guys,

on my M20J I have some strange indication problemes.

The oil pressure went to max, the Oiltemp is in the mid green.

When I switch on the pitot heat the fuel tank indicators drop slightly and the fuel presurre indicator as well.

I suspect a electrical probleme.

Any ideas ?

 

Thx, Axel

[Piloto]

Most likey you have a loose ground connection on the instrument cluster. 

José

 

[defrkm20j]

Thx for the hint Jose,

I suspect the same because I once had this before with the fuel press gauge.

Thx Axel

[Jeff_S]

I'm going to resurrect this thread because I'm having a similar issue. The fuel pressure gauge has a tendency to just drop to zero, and with gentle tapping it will come back up. I have long suspected a ground issue there. But recently I've noticed some weirdness with the oil pressure gauge.

A few weeks ago, I noticed that it would just barely get into the green arc. Oil temps seemed fine on both the JPI and the regular gauge.  The oil quantity had dropped to about 5 quarts which I know should still be fine, but all the same I added a quart and half to see what would happen.

Sure enough, on my next flight, a short hop around the area, oil pressure got into the green and stayed there. Then a few days later, I did a 45 minute flight to visit my parents during which the oil pressure stayed in the green on the way out, but after a two hour lunch visit on the trip home it stayed just at the bottom of the green arc.

Tonight, I wanted to do another test. Still 7 quarts of oil on the dipstick, but this time the oil pressure never got into the green, and stayed right at 50 lbs for the whole flight. Oil temps showed no abnormalities on either instrument.

The oil pressure gauge isn't bouncing around the way the fuel pressure does, so it doesn't seem to me like just a bad ground. Any ideas what would cause this?  I've called my A/P in to get things looked at, but I'm always open to the wisdom of the masses.

[Magnum]

I had problems with my oil pressure, too, no bouncing but sometimes reading too low. It was the transducer, around US$ 800.

Call Mooney , they can give you a schematic for building a test plug. You can attach it to the cable of the indicator and check the reading. You just need a AMP connector and two or three resistors (approx. US$ 20)

Edit: found the schematic

[Jeff_S]

We've isolated this down to just a faulty needle in the gauge. A few slightly-more-than-gentle taps got it to register back where it should, but cycling the instrument breaker showed that it seems to be sticking so now we're investigating the repair/replace options.