Some may recall from MM I had a similar battery problem in my Sierra, a few
odd things happening but the main one being partial or complete battery
discharge after a few days of sitting. After a boost, it would show normal
charging on the ground at run-up, and would be fine as long as it had
regular use.

After a lot of parts and two sets of batteries (one set froze solid) the
mechanic found during the annual....and was good enough to admit it..... a
corroded or loose wire somewhere in the alternator cable in front of the
firewall. When this was fixed, all problems were solved.

I completely trusted my mechanic to find it, it took time, effort and money
and I think no matter where I would have taken it to, they would have had to
either go through the same deductive reasoning all over again, or use what I
had done before as a base to go forward on. Either way, it likely would have
cost the same unless some shear luck stepped into it.

This took a year and a half to solve and caused me no end of grief...maybe
your problem is similar?

Ed Fitchett

----- Original Message -----
From: "Bob Steward" <>
To: <>
Sent: Monday, July 11, 2005 11:25 AM
Subject: [inbox] Re: [musketeermail] Still no luck

> >I have written about my discharging battery problems. This mechanic
> >has gone through three alternators and two voltage regulators. Now,
> >He is sending the original out for a re build.
> >
> >I can not find any information in the archives and downloads on this
> >topic. Can someone please help. It has been nearly two months and I
> >have not flown the plane yet.
> Let's start with a "Mechanic-ectomy" so that you can get someone that
> actually understands charging systems. Throwing parts at the problem is
> obviously not working for him THIS time.
> There are a few basic measurements that must be made, and with that
> information the right part can be installed (if any parts are actually
> The fact that he's wasted more than $1000 of your money on 3 alternators
> ($330 each) and 2 regulators ($115 each) and STILL has no clue what's
> wrong, ought to be reason enough for you to dump this loser and ferry the
> plane to someone that CAN fix it.
> I think that Mike Rellihan has already advised you to check the BAC
> archives, since Yahoo messed up the search function a long time ago, and
> you can not effectively search the MM archives for older topics.
> What one MUST know, before even starting the engine:
> Battery voltage = 12.6V fully charged
> Verify voltage TO the VR on the "S" terminal = within 1 volt of battery
> Verify voltage FROM the VT on the "F" terminal = 6-10 Volts
> Measure resistance from wire removed from F terminal to ground ~4-10 ohms
> After this is known, then you can see if the VR has power and is exciting
> the alternator. If there is no power TO the VR, then its a fuse/CB/wiring
> issue and you trace the wires according to the factory maintenance manual
> wiring diagram.
> If there is power FROM the VR and there is NOT an open or shorted circuit
> on the wire taken off the F terminal and measured to ground, then the
> windings in the alternator are probably OK, as is the wire TO the
> At this point, you start it up, and measure the system voltage. If not
> 13.8-14.2V, then you now troubleshoot why the alternator is off line or
> putting out too little voltage. If you did your homework in the above
> paragraphs, then you probably ALREADY found the problem.
> If you can't seem to get the alternator to charge the battery, the step
> BEFORE buying an expensive $300 "aircraft" rebuilt unit is to take the old
> one to AutoZone or Pep Boys and have them spin it up for free. Tell them
> its a 71 Ford P/U with AC, and they can test it just fine. (Actual
> application for the Ford DOFF-10300J alternator found on most Sundowners
> and other 70's Musketeers.) According to Kelly Aerospace, 80% of the
> "core" alternators returned for OH are just fine.
> Personal consultation is available off list. But I'd start by finding a
> REAL mechanic, and ditch this one that fell asleep in class the day they
> discussed charging systems.
> Bob Steward, A&P IA
> Birmingham, AL
> Join BAC today and be a part of the ONLY Type Club for the Musketeer
> Yahoo! Groups Links

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