Electrical Issue

[Clarkie]

Was flying today in the -6 and had an electrical issue inflight. Maybe some of you experts might have a clue what caused this. In cruise about half way to my destination I got a "check amps" message from the AFS-2500. I looked at it and it was showing 0.3 amps and the volts were 11.8 and declining about a 10th per 5 minutes or so. Having a Lightspeed ignition (battery backup too) and being new to the airplane, I banged a "U-ey" (grew up in Boston) and headed back to my home field. About half way back, the amps and volts shot back up to normal readings like nothing ever happened.

My partner had this happen before, but only after the airplane was sitting outside in the drizzle while attending a formation clinic and once while flying through rain (it's a tip-up).

My initial thought was instrumentation, but quickly discarded that after seeing amps AND volts where they shouldn't be. What do you guys think? Alternator going? Brushes wearing? I'm stumped.

[C-FAH Q]

Tom,
I just recently went through a similar situation. I first suspected the alternator and had it tested, it was fine, then I suspected the regulator, which is not a part of my alternator. It was fine also, but I had seen a one line post that someone mentioned to make sure the field connector that plugs into the alternator may have loose connections. I squeezed the connectors so that the blades of the connection were nice and snug in the connector. I have had four flights and had no reoccurrence of any issues.
Hopefully this works for you, electrical issues can be tricky.

[az_gila]

As Gary said,

An intermittent open circuit on the field line could cause your problem.

[airguy]

Sounds like a field circuit problem all right - check power, ground, and breaker for the field.

[RFazio]

Stranger things have happened. When I heard rain I though loose belt.

[Rupester]

Slipping belt was my first thought too.

[170 driver]

I had a similar problem with mine,it was intermittent and was very hard to find,,finally chased it down to a loose terminal on the alt/master switch(B&C toggle),,,the rivet or brad that held the blade lug on the switch was loose,,,I bought a better quality switch and replaced it and my readings have been normal for the past 20 or so hrs now. I changed the alternator and regulator in troubleshooting before I finally found the problem. At least I have spare parts now.

[OneCharlieKilo]

I had an intermittent like that once that went hard failure in flight about 5 minutes from my home field (just happened to be at night too....), then came back to normal on the ground (alternator back on-line) before going intermittent and hard failure by the time I got to my hangar.

My problem turned out to be the main output line nut on the alternator "big" wire output vibrated loose and fell off in flight. The intermittent was the ring terminal making intermittent contact until the high resistance connection melted the solder off the cable/terminal connection (found it dripped and resolidified on my cowl bottom).

I had secured the nut with a star lock washer that didn't quite do the trick, so after repairing the cable I secured with both lockwasher and some lock-tite. Worked fine ever since.

[Clarkie]

Thanks for the replies guys. I'll pull the cowl this weekend and start investigating.