Update Electronics Expert

Moonlite37 · Nov 4, 2015

A few days ago I posted about a battery drain on a Lincoln under warranty and the service technician thought it may be possible that a radio frequency from the garage door closing could be activating some sensor. It occurred again but the technician discovered that it was an intermittent back feed through the alternator and can occur in any location. The alternator is being replaced and the natter is hopefully resolved.

jeffcat · Nov 4, 2015

Aren't electronics wonderful?! Glad that is fixed.

Determined · Nov 4, 2015

(quoted from post at 07:39:52 11/04/15) A few days ago I posted about a battery drain on a Lincoln under warranty and the service technician thought it may be possible that a radio frequency from the garage door closing could be activating some sensor. It occurred again but the technician discovered that it was an intermittent back feed through the alternator and can occur in any location. The alternator is being replaced and the natter is hopefully resolved.

Had to track down a similar gremlin on a customers ford product years ago.
Only happened about once in two weeks and by chance only when the customers wife would drive the car to work, by days end the car would not start.
Tested the system multiple times and no draw on the system was present, battery tested fine, charging system tested fine. drove the car myself for a week and no problem.
Turned out that if the alternator came to a stop in just the right position it would create a draw, enough of a draw that with the key off the shaft at the pulley end was magnetized enough to hold onto a wrench.
Give the alternator pulley a half turn and the draw went away.
A new alternator solved the problem.
Never came across another one like that since.
Hopefully the new alternator solves your problem.

JF in MI · Nov 4, 2015

That sounds weird even if it was a generator. Was that alternator internal regulator? If so I could see an intermittent
transistor latching problem but I think the rotor causing it by stopping in a "certain" position is a fluke. The additional
turn you gave it may have been just enough to "unlatch" it..

Determined · Nov 4, 2015

(quoted from post at 10:43:58 11/04/15) That sounds weird even if it was a generator. Was that alternator internal regulator? If so I could see an intermittent
transistor latching problem but I think the rotor causing it by stopping in a "certain" position is a fluke. The additional
turn you gave it may have been just enough to "unlatch" it..

Likely never know for sure.
Vehicle was an early to mid 90's T-bird, so voltage regulator internal/on alternator.
Was so glad to finally find the problem we just replaced the alternator vs dismantle and test.
Being an alternator with slip rings vs comm sections for the brushes to ride on support's your comment and I am in agreement with you.
Maybe something rubbing bare, worn out bushing, metal dust from bushing/bearing or chunk of brush flying around inside, intermittent failure in regulator, intermittent diode failure which some claim is possible.
Never have come across another with the same symptoms over the years, but for some strange reason I always touch a wrench to the alternator pulley shaft [key off] when I am under a hood.

MARK ROBKE · Nov 4, 2015

When I was still working on trucks(recently retired),I found alternators causing a draw quite a few times.Sometimes you could feel the alternator was warm to the touch on a cold engine.With 3 or 4 batteries,it might take a weekend to discharge the batteries to the point of not cranking,and yet the alternator still charged.Mark

JF in MI · Nov 4, 2015

That is a strange one and is the reason, when I was in the business, I quit saying "now I've seen everything" because I
learned that soon enough I would be repeating saying that. What bothered me is that most of the crazy stuff seemed to happen
to my own vehicles. Just like last week; Driving along and my Ford Club Wagon just "turns off". Not even any emergency
blinkers. After being towed home I knew there was only one thing it could be; main 100 amp fusible link to the chassis
melted. There was only one wire capable of carrying 100 amps and that was the alternator output. Turned out one of the diodes
"vibrated" out and shorted the whole rectifier grid. Never seen anything like that before in 26 years of professional
mechanic. And that's just one of my own car weird problems.

Bryan inIowa · Nov 4, 2015

Some shops are using thermal imaging cameras now. Great for finding current draws. stuck relays , bad j-joints. I would love one, but two - four grand is not in the budget yet .

Andy Martin · Nov 4, 2015

(quoted from post at 12:41:18 11/04/15) That is a strange one and is the reason, when I was in the business, I quit saying "now I've seen everything" because I learned that soon enough I would be repeating saying that.

When we made a mistake at work and someone said "we learned our lesson on that one" I always reminded them that there are lot's more lessons left than days.

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Moonlite37

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jeffcat

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Determined

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JF in MI

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Determined

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MARK ROBKE

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JF in MI

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Bryan inIowa

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Andy Martin

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