What is a Capacitor function attached to my fuel gauge instrument?

[Cesarmx]

Good morning everybody

My Beechcraft sundowner left fuel gauge instrument has a red round disc capacitor whose one leg goes to ground for that instrument but the other leg is attached to nothing ( I presume it goes to the ignition post but it has been disconnected for 25 years of my ownership and I discovered by accident when I replaced the oil temp indicator in that cluster ).
Any ideas what it is for? Should it be connected to close the circuit for that left fuel gauge instrument?
Note: The right fuel gauge instrument has no capacitor installed ??? I just wonder…




Thanks for your inputs!

 

[Bell206]

My Beechcraft sundowner left fuel gauge instrument has a red round disc capacitor whose one leg goes to ground for that instrument but the other leg is attached to nothing ( I presume it goes to the ignition post

I can't make out details on my phone, but if its similar to a Y capacitor I've heard of people using one to filter or control EMI noise. Perhaps get a factory wire diagram and check your install to see if any changes, then have your mechanic verify it. And if its not connected or required then simply remove it. You may also research your logbooks to see if it had a system noise problem in the past and what they did to correct it?

 

[Palmpilot]

Good morning everybody

My Beechcraft sundowner left fuel gauge instrument has a red round disc capacitor whose one leg goes to ground for that instrument but the other leg is attached to nothing ( I presume it goes to the ignition post but it has been disconnected for 25 years of my ownership and I discovered by accident when I replaced the oil temp indicator in that cluster ).
Any ideas what it is for? Should it be connected to close the circuit for that left fuel gauge instrument?
Note: The right fuel gauge instrument has no capacitor installed ??? I just wonder…

View attachment 151226


Thanks for your inputs!

I don't know the answer, but one those nuts looks like it close to falling off.

 

[Barrett50]

The little cap is for needle response smoothing. Sometimes its included inside the instrument case, sometimes outside sometimes not needed for the type of sender.

 

[Cesarmx]

I don't know the answer, but one those nuts looks like it close to falling off.

Yes, I loosened both nuts to see better for the wire connections, looking up while lying down underneath the avionics panel surrounded by bundles of wires, cables, hoses etc and at 14 + inches distance is hard to see….

 

[Dan Thomas]

The little cap is for needle response smoothing. Sometimes its included inside the instrument case, sometimes outside sometimes not needed for the type of sender.

That's a picofarad-level capacitor and wouldn't do much smoothing for the larger current flow in a Wheatstone Bridge meter circuit. About all it would do is absorb a bit of RF.

 

[Cesarmx]

That's a picofarad-level capacitor and wouldn't do much smoothing for the larger current flow in a Wheatstone Bridge meter circuit. About all it would do is absorb a bit of RF.

Thanks for the feedback!

 

[Barrett50]

That's a picofarad-level capacitor and wouldn't do much smoothing for the larger current flow in a Wheatstone Bridge meter circuit. About all it would do is absorb a bit of RF.

And yet, that's what it's there for. The current flowing through the meter is in the microamp range. It doesn't take hardly anything to damp needle swings. To test, remove the cap, and go for a bumpy flight. You'll see.