Alternator light came on today

[Build9A]

Took off today to heat up the oil for an oil change and noticed the alternator light flickering on and off, mostly on. After about 15 minutes I landed and pulled the cowl and checked all the alternator connections. All seemed secure with "maybe" one that I was able to tighten a little at the panel.

Changed the oil and then tried to start the engine. Nothing happened, prop wouldn't turn. Looked over at the fuses and noticed that the alt field fuse was popped. Pushed it in, turned the starter and engine started as normal. Alternator light off and alternator charging normally.

Could the suspect connection have caused the popped fuse and alt. light to flicker? I haven't flown it again cause I left the cowl off to continue to troubleshoot.

Any thoughts or suggestions would be appreciated.

[CESSNADON]

A popped field breaker on the alt. should make the alt light come on, steady, not flickering. Replacing the fuse to turn the starter over doesn't make sense to me. The alt field and the starter solenoid should be seperate circuits...I'm speaking from Cessna experience...Perhaps the RV's are wired differently.

[gmcjetpilot]

Originally Posted by Build9A

alternator light flickering on and off, mostly on.

Good chance it's a poor connection. The light can also mean an alternator fault, no charge, low voltage and even an over voltage, depending on the logic in the voltage regulator. That ALT light can be more than no charge. What was the volt meter doing? What was the load meter doing (if you have one)? Other wise I would not worry about it.

The connections coming off the alternator take a beating vibration wise. I have been stumped and baffled by some poor crimp connections that looked OK but where not (electrically) good. Pull on them and look for any movement in your terminal crimps. Really look close for broken strands. IF IN DOUBT ABOUT THE CRIMPS, GET NEW TERMINALS AND RE-DO THE CRIMPS. Strain relief with heat shrink and supporting the wires so the crimp terminals are not supporting the wires is goodness.

We safety wire all these structural nuts and bolts but rely on very little to keep the wire connections tight. Don't over torque of course. I never did this but I wounder if just a drop of loc tight might not be a good idea?

How many hours on the alternator? Check the brushes if more than 200 hours. Should last longer but who knows. It's possible the brushes where chattering? Just pull the shield off the back and remove the brush holder and look at the slip rings and brushes. Any thing not look right? The spec for the brushes are:

Std BRUSH LENGTH 0.43", Min Service Limit: 0.20"
(amount of brush sticking out brush holder assy)

The next step is remove the regulator and rectifier and do simple test with a multi meter, checking VR condenser capacity and diodes, but there are special testers that can check these components more completely. It could be the voltage regulator going flaky?

(Suggest operational procedure: Turn ALT switch on before engine start and leave ALT switch on till engine is shut down. That is the way the regulator was designed to work. Flipping switches while alternator is spinning is suspected in damage to regulators.)

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(Note: I don't guarantee the above spec is for YOUR Alt, but this is from my Suzuki Samurai manual. This vehicle uses a similar ND style/brand alternator to the generic clone Van sells. Specs change so beware.)

[Build9A]

Ever since I tightened the suspect connection, everything has worked fine. I have about 10 hours since tightening and so far OK. I was curious if the intermittent connection could have caused the fuse to pop?? take care and thanks again.