Story of an Alternator partial failure

[rocketbob]

Originally Posted by Wayne Gillispie

Try calling your car alternator manufacturer and
ask for troubleshooting advice.

Or you can come here and get quick advice in a matter of minutes.

[douglassmt]

Originally Posted by Wayne Gillispie

Like Bryan, my first airplane, first(hopefully last) build and went with what Van's recommended. We have two batteries 925/680 with enough power to complete a 4.5 hr flight if needed. We can recharge overnight and return home the next day to repair too. We also set low voltage warning slightly below the normal 14.2-14.3.

Bryan, Do you have the cooling blast tube on alternator? What about metal shield protection from #1 exhaust pipe? I don't have either but have measured 300F degrees surface temps on side of alternator facing exhaust pipe. No telling what internal temps are running. Wish I had an embedded thermistor sensor. No, my truck alternator does not run that hot!

I have neither on mine. I asked Dick about temps and he said it's unlikely to be a problem. They are rated/tested to 300F and it might only be a concern if I'm running at max amps capacity of the alternator (I'm not) in a very hot climate (negative). It is interesting you got 300F on the side of the alternator, so that might be something to think about.

[douglassmt]

Originally Posted by Walt

From my experience only... B&C has the best track record on alternators.

Also curious why you didn't have a voltage alarm or notice that the voltage was lower than "normal"?

Walt -

Part of the anatomy of this failure is that it appeared to be gradual, initially intermittent, and was always partial. The other part is that the knowledge/experience/aptitude of the operator was also intermittent/partial I did not have my voltage alarms turned on (do now) and did not notice the voltage being low until very late in the process. I'm pretty sure they were fine initially, but again I certainly wasn't as attuned to that as I am now. The reason for the post was mainly the second part - those of us who aren't expert in matters electronique can learn from each others mistakes.

[Wayne Gillispie]

Thanks for posting. It will especially help those with VP systems. Glad you got it fixed and no damage to you or your avionics.

[Walt]

Ahh... but you don't have to be an expert to "Listen" to your machine

We should all know what "normal" is for our aiplane, normal sounds, engine indications, control feel, etc. are critical, so when something changes we should take notice and look into why before we go flying again.

Your initial post with multiple popping CB's/resetting/go flying and then repeating this exercise multiple times, with hopefully different results, could have been a recipe for disaster.

This is exactly what the NTSB report is all about

When something is wrong your machine it will inevitably try to let you know, the question is:
1) are you listening
2) do you choose to ignore

Please realize that I am not trying to be critical of you or your abilities, I just want folks to be safe out there!

[douglassmt]

No offense taken, Walt. I deserve some of it, maybe all. And the discussion is healthy.

The popping CBs were intermittent at first, and the reset worked in most cases. They didn't happen every flight, maybe every third flight. Only when it became a "cascade" and the CB wouldn't reset did I stop and troubleshoot. Also, on the VP-X, the CBs are adjustable, so "nuisance" trips can occur if you've got the CB value set too low. I've also heard from others of CBs tripping for no apparent reason - occasionally. So, while I was probably patient with this for too long, I wasn't completely oblivious.

[roee]

I'm still curious as to why exactly the VP-X ECB's tripped. Did the voltage fluctuations caused by the faulty alternator somehow cause actual over-current events on those load circuits, which the VP-X correctly detected and handled? Or is the VP-X itself somehow susceptible to voltage fluctuations, and as a result, erroneously detected over-current events on those load circuits when really there were none?

Perhaps Marc Ausman could chime in?

[Walt]

"By this time I'm getting frustrated. I repeat the runup (when the 327 now trips every time) while monitoring the amps for the problem circuits. Well now, at idle, the two circuits are drawing 0.4-0.7 amps, but it wavers a little. At about 1400 rpm, the amps go crazy, bouncing from 0.4 to 13 to 30 to 22 to .5, until eventually the 327 trips (ECB set at 3 amps)."

Obviously the units cannot draw the amp readings above, so the voltage fluctuations to the VPX must be causing the erroneous amperage readings in the VPX somehow.

[6 Gun]

In reguards to post #3 I think you can run down to local parts and get same Alt looks like my suzuki samurai

[TS Flightlines]

i'm alittle curious: What caused the stator windings to break at 250 hours?
Tom