Dead Battery

[Bill B]

My brand new battery was dead this morning. The alternator checks out O.K. I assume something is drawing the juice out of the battery. How do I check this out? Many thanks for any help.

[Joe K]

Alternator? How do you mean check? Diodes?

You can check this by charging the battery remotely (battery charger.) Undo your generator connection. And then re-connecting the generator with an ammeter inline in the circuit. Be prepared to "undo" the connection quickly if you find current though as the current may be beyond the capacity of your meter. Current without the alternator turning usually means a bad diode.

Take heart, the same issue on my 2003 VW TDI cost over $800 to fix - and this with a factory reman alternator.

I've heard of people using a common magnetic compass to determine current flow instead of an ammeter. At the farm we had a sort of meter based on the Boy Scout principle that I would hold close and you could see the needle move if there was a current in the wire.

With the circuit diagram and the meter in the dash you can diagnose a lot of electrical problems. It's a pretty simple system. You might even remove this meter and use it on the generator output wire directly - that if you don't have another kept as a spare.

Or you might have the dreaded stop light switch issue (stop light switch leaves the rear tail-light "on" and you walk away not realizing it. )

Or you might have the "Non-popping popout switch syndrome" which when you shut down disconnects the distributor from the circuit, and grounds the protected cable, but lies about the first of these two (stays connected and grounds out your system.)

Or any other number of maladies relating to a ground somewhere in the system. This becomes a sort of "disconnect and check for current flow when everything is off" sort of one by one trial.

Get yourself a good circuit diagram of your particular car if you can. A couple of respondents have provided these in just the last day. You can google Model A circuit diagram and come up with several versions.

And have fun. Nothing provides a reason for a nice little mug-up afterwards when you have your "AHA" moment.

Good luck,
Joe K

[Hicktick]

This is what I would do . Charge the battery back up and check to see if your brake light is staying on .

Its the most likely thing that will drain a battery .
If thats not it then do you have a test light ????

Take a test light and put it inline with the battery positive .
In line means take the terminal off of the battery post and connect the test light from the battery post to the removed cable end .

If you have a draw , the light will light up .

Start disconnecting things one at a time untill the light goes out .

Most likely its your brake light switch or your alternator , but could be horn, lights , or ign. system .

[JBill]

You might try reattaching the cables, just in case you didn't get them quite snug enough. Just grasping at ideas.

[Herb Concord Ca]

Hi if you have a starter mounted fuse, remove it when your done driving for the day. Most 6V alternator have a leakage path to ground and your battery will discharge over a few days. To avoid this just remove the fuse.
That what I learned to do 20 years ago.

[Greg out west]

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Hey Bill,


Did you check the battery itself ?, Maybe a bad cell ? I remember you coming in the shop I used to work at "Automotive Part's"...I'am down the hill in San Pedro,,,


Stop by if you like & I'll see if I can figure it out.


Greg out West

[Tom Wesenberg]

Is this a duplicate post?
I'm tired, but I'm sure I responded to this already.

[BILL WILLIAMSON]

Originally Posted by Herb Concord Ca

Hi if you have a starter mounted fuse, remove it when your done driving for the day. Most 6V alternator have a leakage path to ground and your battery will discharge over a few days. To avoid this just remove the fuse.
That what I learned to do 20 years ago.

This is an old TALE, Herb. While in the hospital, Minerva sat for 4 months, with a 6 year old battery, & NO charger or maintainer & BANGED off as if just run yesterday! I only EVER used ANY charger, except when I left the dash light on for 3 days! Bill W.

[P.S.]

Hi Bill,

Before you get too far into this... How old is your battery? Is it full of fluid? How cold was it when the battery drained overnight?

Whenever you come out in the morning and your battery is dead, always start by putting a charger on it and then checking to see if any lights or the ignition was left on BEFORE you start moving things around. What drained the battery is good to know.

If a battery is old enough that the cells have begun to calcify, you'll usually have some notice with one or two cells becoming shorted and showing up as low battery voltage after sitting for a while. A bad alternator would show up on the Model A ammeter as a drain, even with the car off.

The bad part is that once you run a lead/acid or gel cell battery that far, it never comes back up all the way. Running a battery that far down ruins it. Even if you put a charger on it and bring it back up, it's doomed to fail very soon and replacing it right away is the best solution.

[Herb Concord Ca]

Hey Bill in Frenso, don't want to argue with you but in my case it wasn't a TALE.

My 6V alternator had a leakage path to ground with all the wires removed.
It's been that way for 20 years! Never took the trouble to investagte it.
For me it's easier to just take the fuse on the starter out when I finish driving the A for the day!

[BILL WILLIAMSON]

Originally Posted by Herb Concord Ca

Hey Bill in Frenso, don't want to argue with you but in my case it wasn't a TALE.

My 6V alternator had a leakage path to ground with all the wires removed.
It's been that way for 20 years! Never took the trouble to investagte it.
For me it's easier to just take the fuse on the starter out when I finish driving the A for the day!

Herb, Dog here, Ol' Bill asked me to apologize for him, he's bizzy tryin' to get the self cleaning thingy figgered out on the oven, he'll be up half the night to see if it worked!! Not ME!--ZZZZZZZZ Buster T.