alternater woes

[OSCARDEUCE]

I need some help.
Flying home Sunday my ammeter went to 0 and the rear alt went out, tried resetting, but that did not work. the front alt worked. ammeter still at 0 with load (landing light) and both alts off. any ideas where to start looking?
I have a 1968 O2-A
Tom

[GMAs]

Start reading all the past articles we have written.. about how to test your system...

Its kinda like a class I took on screen writing... and the guy that was giving it was a director... he must have hated screen writers because he was not too kind to them when they tried to explane their work... he told us that writers were not supposed to interfear with the creative mind of the director... but, wanted us to come up with thought provoking ideas... to spur the creative director...

I thought and thought for a min.. and after hearing all the rest that gave detailed acconts of their scripts... which was appearently the wrong thing to do with this guy... when he came to me... I said....

Ahhhh my script is kinda simple.. and direct...

director: ahhh I like that... because it gives me freedom to creat what I want.... without writers telling me what to do...

What is it he said... go ahead lay it on me... and I will expand from your suggestion...

Ok.. I said... opening ... world war 3 begins...

and then I smiled at him as he had a puzzled look... director: thats it... thats all you gave me to work with... Yep I said... it left a lot of room for his creative judgment... huh...

Well that is kinda what your saying here... it broke and it needs to be fixed... smile...

How about some background, conditions, voltage measurements... etc... without them we can't start you out in a direction to find the bad part...


So where to start.. well how about he alternators themselves... check the mechanical stuff... like the drive couplers for slippage...

the brushes for wearing out...

the diodes for going bad...

etc..

regulators usually are not the bad guys... so don't go fiddling with them... just yet...

wiring is the next thing that you need to check... for contenuity...

You didn't mention how many hours on them... or the engines.. etc...

so help us out ... give us some idea of what the system was like and what has been done... ??? GMAs

[Guy Paris]

Tom,
I don't know if the early 337s have the same type of alternators that I have on my G model, a 1977. My alternators have an internal fan a squriel cage type. If so see if thats in tack, that it wont just rotate freely. If it does then the coupling bushings/hub assembly or the shaft would be suspect. If its in tack, does not rotate freely, the alternator or its wire connections would be suspect. I have had both problems. Guy.... old72driver....

[skymstr02]

Oscar, take off your left rear cowling, using a voltmeter check for battery voltage to the small post on the rear of the alternator. If you have in the neighborhood of 24 volts there, then chances are that the alternator shot craps. The rear belt drive alternator on the O-2 is the same unit on a '78 to '82 172 (24v, 60A) and finding a rebuilt unit shouldn't be that much of a problem.

Dave
O-2A
68-11055

[OSCARDEUCE]

Hi,
Thanks for all the input, I found 2 loose wires on the rear alt, fixed em good. Thoughbt I would go flying. No output from rear alt. uncowled everything in back and too off rear alt.. It was FUBARed. Will put in new and let you know. Thanks for all the help.
Tom

[GMAs]

When we went thru mike swanson electrical system we had some real funny things happen... like the alternator would not put out until it got up around 1800 eng RPM... we took it off and sent it back .. it was overhauled... again and they could not find anything wrong... we put it back on.. and guess what.. it stil didn't work right... so it was pulled again and sent back.. this time they took the rotor out of it and replaced it... seemed to work find after we put it back in...

Moral of this story is to have it bench checked for performance at your local shop bench first... as we have gotten ones that said 24 volt and they only put out 12.. smile.. not real fun taking them on and off... all the time.. so check it out first even though it says new.. check .. check... G.M> GMAs....