Nav lights with unequal voltage?

I recently bought a 2003 built RV-9A. Very nicely built but with a few squawks due to age. The left Nav light works fine and shows just under 12 volts while the right one shows only about 2.5 volts. Both lights are in the fiberglas wing tips and seem to use the ground from the strobes which is wrapped around one of the screws holding the light on as the return. The Nav lights only have a hot lead and the ground is thru the body. The strobes work fine. Why would one work with this system and not the other. I haven't tried running a separate ground lead from the Nav/Strobe fixture to the plane body yet.

Try running a separate ground for your meter as a test. Then measure the hot wire. If you get full voltage you will know you have a problem with the ground path. If you don't you have a problem with the hot wire. The meter draws very little current so any wire should work.

Low voltage indicates a bad connection(s) in either the hot or ground side.

I tried putting the meter ground on one of the SS screws holding the wing tip to the wing - figuring that it went into a nutplate on the aluminum of the wing. Got the same voltage reading. I'll try it with a longer wire and alligator clips to a bare aluminum part of the wing tomorrow. Guess it could be the hot wire and not the ground that is the problem.

I know a lot of people use the frame to carry ground for lighting and etc. I won't be doing that. I just don't think it provides a reliable ground connection.

I used to have this horse trailer where the manufacturer had used running lights where the ground was through pop riveted connections to the frame. Oxidation developed and the lights were always intermittent. I would have to bang on them which moved them around just enough to get the connection back.

I realize a plane isn't a horse trailer but some of the same problems apply.

Flyer2017 said:

the ground from the strobes which is wrapped around one of the screws holding the light on as the return

Click to expand...

Do you mean the strands themselves are wrapped around the screw and the screw tightened? That is, no ring terminal connector crimped onto the wire?

If so, that's a no-no in aviation. I'd be looking throughout the plane for similar connections...

Flyer2017 said:

I tried putting the meter ground on one of the SS screws holding the wing tip to the wing - figuring that it went into a nutplate on the aluminum of the wing. m.

Click to expand...

If it's the same design as the -10 then the nutplate is on the fiberglass. There needs to be no paint under the screw head to get a good connection.