Cowl Flaps cause fuel gauge to fluctuate. ?

[Glen Davis]

This is in my friends 1981 M20K

”Crazy analog right tank fuel gauge!! 
If I push and hold the cowl flap knob firmly closed the right fuel gauge reads accurate fuel quantity!  As soon as I release the pressure, it will open an inch or two and the gauge reads inaccurate.  Not sure if cowls flaps are closing completely in flight, maybe partially with wind pressure, or staying open in flight.  They close and open on the ground.  So, why will my gauge read correctly if I keep pressure on the cowl flap knob in the cabin but fluctuate and even go to zero when I release the pressure?

[Fly Boomer]

16 minutes ago, Glen Davis said:

This is in my friends 1981 M20K

”Crazy analog right tank fuel gauge!! 
If I push and hold the cowl flap knob firmly closed the right fuel gauge reads accurate fuel quantity!  As soon as I release the pressure, it will open an inch or two and the gauge reads inaccurate.  Not sure if cowls flaps are closing completely in flight, maybe partially with wind pressure, or staying open in flight.  They close and open on the ground.  So, why will my gauge read correctly if I keep pressure on the cowl flap knob in the cabin but fluctuate and even go to zero when I release the pressure?

Crazy electricity.  

[DonMuncy]

I would look for a grounding wire a little loose. Easy enough to use a wire and a couple of alligator clips to make a temporary ground to check (although a PIA to get back there to hook it up).

[PeteMc]

Crazy how the littlest change can through something else off.  I'm wondering if when you let go there's enough flex to move some wires and causing the grounding or connection issue that @DonMuncy is talking about.  I had kind of a "heart beat" in my cluster gauges (K) which we all knew had to be a grounding issue.  Mechanic just moved the ground when it was in for the last Annual and everything cleared up. 

And personally I go by the JPI and the in-wing gauges for accuracy.  Never trusted the ones in the panel. 

Edited November 14, 2023 by PeteMc