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Alternator Failure...Sort of

petehowell

Well Known Member
We left Saturday morning to pick up a few rescue dogs down in Wisconsin, but not far from home base, the Dynon EMS says we are undervolt. Odd - no alt failure light on the dash.....Hmm

OK Rtn to Anoka. Bernie was on my wing in his 7A with Kate, and he says we can use the Bonanza for the trip - and a good one it was. Pics here:

http://picasaweb.google.com/trackker.ant/PnP5000#

You won't find a better friend, RV or otherwise than Bernie!

Back on the ground, I pull the cowl and bingo!, the solder lug on the B terminal is cracked. Easy fix I think - I installed a new connector, checked the other wires and pull it out for a test run. No joy. Hmmm.

OK, (I think) the main wire broke and it dumped the alt load and trashed the regulator. That must be it. I pull the alt, grab the lifetime warranty receipt and Head to Oreilly Auto. They put it on the tester and it is fine - maybe a tad weak (13.8) so they handed over a rebuilt, same as a mine, only cleaner and with lots less hours on it......Hmmmm. I was only seeing 12V so this is not the whole answer.

Back at the hangar. I pop on the new alternator, and I check both the B-lead breaker and the field breaker. They are fine. Hmmmmm.

I check and have 12V to the field wire in the cockpit....Hmmmmmm.

I check for 12 V on the field wire at the connector. Nothing. Ah-Ha! (alt needs 12V on the field wire to produce juice). I did have 12V about 12 inches up stream where I spliced the Vans ND connector into the plane wiring. I cut the connector out and found the field wire broken just sort of the alt connector. The insulation looked fine, but the copper was completely broken. The wire quality on the Vans ND connector was not the best..... Now it makes sense the ALt failure light did not work, you need 12V on the field wire for that to work!

I rebuilt the connector using aircraft wire and terminals and potted the backside to provide better strain relief. The original connector went 550 hrs, maybe this one will go 1000.

Rotec%20TBi%20003.jpg


Bernie helped me install the new connector this morning and all is well with the world. :)

I'm sure many of you would have figured this out much quicker - but I wanted to document in case it might save someone a few hours. To be honest it was kind of a fun puzzle and now I know that part of the plane is in better shape.

Side note O'reilly has all your receipts online, so if you are on the road and need a replacement alt - they can look it up for you and have one sent - not a bad deal!
 
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This sort of thing

Persuades me to throw in a cheap $3 eletric multi meter in the tool bag for those long cross countires.

Frank
 
Pete,

Good write up. What is the part number of the Oreilly alternator? I'm running a B&C right now, but I have seen the wisdom of using a commonly available unit. Never to early to start planning for my next alternator failure.
 
RV'ers sem to drive '87 Samurais than any other vehicle! :)

Nice fix Pete. I have also done away with the ND connector altogether when I couldn't find one - the guts are just blade connectors, and you you can build the cable with crimp-ons if you need to. It helps to have the wiring diagram handy so you get them in the right place.

I also like the idea of adding a cheap DVM to the tool kit - at least for long cross-countries. Of course, these days, you probably have an RV builder within a short distance of anyplace you might land....

Paul
 
Alternator Update

2000 ft over KSTP last night I noticed my volts were down to 13.6 from my usual rock steady 14.2. STP tower gives me a 180 and direct Anoka, land at 13.5 V.

Cowl off, 15 min later I am at the O'Reilly a mile from the airport, show them the scanned warranty receipt on my phone, they test the alterator and confirm the output is low. They do some paperwork and I walk out with a fresh rebuild.

My Suzuki has a new dynamo, and I am rock steady at 14.2 once again. Pretty painless as far as repairs go..... this one went about 700 hours, brushes and bearings looked good - smells like a regulator kerfuffle....
 
Great write-up Pete. I have a collected memory of several of these alternator connector issues, so this prompts me to pot mine for the original installation maybe even install tefzel too. This is coming up soon.

Thanks!!
 
Bill - glad I could chip in - I really value your posts, I always learn something from them!!


Great write-up Pete. I have a collected memory of several of these alternator connector issues, so this prompts me to pot mine for the original installation maybe even install tefzel too. This is coming up soon.

Thanks!!
 
Update.....at 1570 hrs

Showed undervolt (13.4V) again over the weekend at 1570 hrs, so the connector did go ~1000 hrs +. I tweaked the fastons(tightened the blade grip connections, and I was back at 14.3ish volts again.

My PC680 sent me a thank you note....

I might pull the connector and tweak the fastons at annual time to stay ahead of it, although "on condition" might be ok as well.

That is all.....carry on!
 
I've ran into more than a few planes where the crimp connector literally broke in half. Potting the wires as done in the original post prevents future breakage but I further it a bit by building the silicone potting to extend out about 1/2" around the wires to take all the vibrational stress away from the connectors.

Keep 'em flying!
 
Sensor safe RTV

What did you pot the connector with, Pete? My plane power plug has already done the same once. Need to try and head off #2.

Hey Steve,

Sensor- safe RTV. Seemed to work well. I think 1000 hrs of vibration and my landings just takes it's toll......
 
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Rebuilt original

Where can I find these new connectors?


Hi Blain,

I just removed the wires and crimped connectors from the original connector and replaced it with quality aircraft wire and crimped faston connectors. I then potted the whole shooting match with sensor safe silicone sealant.
 
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