Need help chasing electric gremlins

[AHaury]

Thanks all for the input. Keep it coming if you have any other thoughts.

[Captain Avgas]

Originally Posted by AHaury

had an incredibly strong electrical burning smell.

I'm not very electrical smart, but need some basic suggestions on where to start.

A burning smell....whoaaa. I recommend that if you are not, by your own admission, savvy about electrons, then get out your cheque book and engage a professional. An avionics pro will probably locate your problem in a few minutes. Left to your own devices you might just end up with an inflight fire or an avionics failure during an IFR flight (or both !!!).

[BillL]

Also, remember there are so called crimps in those heavy power wires. The standard pull test for a AWG2 termination is 500 pounds, yes, five hundred.

Think about where the power goes, and what the starting and power supply function have in common. Check everything, look for shorts, wrench, pull (hard) and wiggle every single connection. Power and ground side. This is just to begin.

You can check charging after finding the source of the disconnects. If you don't have a good handle on how to do the diagnostics, and proceed with a definitive plan, then employ a qualified person to lead the effort. (or keep asking here ) Guessing will let to several expensive parts replaced until someone stumbles on the real cause. Don't assume anything.

[rvmills]

Edit, saw Bill's post above after I typed this, so here's my sample of what he was talkin' 'bout…

Another item you might add to the list of checks is the wire crimps on the related wire fasteners. I had a wire break inside a spade fitting on my original alternator, which caused intermittent drops to zero amps (and the resulting drain on the battery and electrical system). Looked fine from the outside, but in flight it would vibrate loose at times. A gentle "pull check" found it, and solved the mystery. So along with the components all have listed to check, I'd just add the wires and fasteners. Good luck!

Cheers,
Bob

[AHaury]

Originally Posted by BillL

Guessing will lead to several expensive parts replaced until someone stumbles on the real cause. Don't assume anything.

Roger that. Hope is a horrible strategy. I have today off and the prediction is rain so off to the hanger to start checking things.

[TylerII]

Please first confirm that the ground from battery negative to engine block is less than 3 milliohms and that the airframe to negative post is the same or less. The engine controls i.e. throttle, mixture, and prop becomes ground and can get very hot if the engine to airframe ground id not correct. Note that the lack of good negative connection is often a source of the issues you describe. Electrons flow from negative to positive.

After determining the negative connection is good move to the master then starter solenoid. There the best best method is remove and replace as the cost low compared to alternator regulator issues. The suggestion about the alternator connections are the net step.

Tyler
A&P, FCC GROL
N174MT

[rpellicciotti]

I'll just throw this out there for consideration. I have actually seen this on an airplane in our shop. Master solenoids are designed for continuous duty. Starter solenoids are for short engagements. I saw a case where a starter solendoid was installed as a Master. It worked for awhile but began giving trouble after a few hundred hours.

[spark68]

To add to the good advice already given.

You may just have more than one discrepancy. Best to check all the way through these primary circuits from battery to ground, battery to starter, alternator to battery and primary bus. You may find several termination points that can be cleaned and/or tightened, reducing resistance and increasing voltage available.

[E. D. Eliot]

Suggest that you don't fly until you find and replace the burned component. This may be in addition to the real cause of your problems. Also, look for the reason that the burned component apparently wasn't fused properly. You don't have to look 'way out there' for the solutions to these problems - they are right there in front of your nose - use it to help you find the burned component. Good skill!!!

[AHaury]

[quote=TylerII;965975]Please first confirm that the ground from battery negative to engine block is less than 3 milliohms and that the airframe to negative post is the same or less.[quote]

Tyler, these connections are secure, but how is that checked?

Thanks to all for the input and for those who are "plight following" here's an update. Pulled the cowl this morning and started at the battery checking all connections. Didn't take long to find a loose connection between the starter solenoid and the connection on the firewall. This also has a score mark on it like it may have sparked. Cannot find anything that even looks like it was burned or hot. Looks like I probably have a loose alternator belt also.