Thread: Battery Draining

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Here is a quick clip of how to test the charging system down and dirty straight forward.

How to Test Alternator Voltage Output (AutoUpkeep.com) - YouTube

But I thought your problem was battery drain, I am now lost. What are you trying to solve ?

Trying to find the source of the drain. When I do that same voltage test it drops when running. I've taken the alternator down and had it tested. They said it was good. I'm just going to put a new one on.

Is the alternator a one wire or three wire install ? I ask this because a one wire needs higher RPMs to start charging. If it tested good and it is a one wire alternator the voltage drop is cause by the fact that the car is running off the battery voltage.

Now the drain:

Using your meter, remove the + battery cable. Select the amp setting on the meter. Hook the black lead of the meter too the + battery post. Then the red meter lead too the + car cable. You are now ready to check for the source of the drain.

At this point you should see some sort of amp reading, the reason will be the circuit is active and draining the battery. Just what you thought and are looking for. Now how do we find that source?

Let’s say your fuse box has 6 fuses. Divide the fuse panel in half, top too bottom or left too right. Remove 3 fuses, check the meter, if it reads 0 then you now know one of those 3 circuits with the fuses removed has a fault. Install 2 fuses, is the meter still reading 0, bingo that last fuse still removed is in the circuit that is not playing nice.

If you find that when the first 3 fuses were remove, let’s say from the bottom half. Checking the meter you see it is showing a drain. Simply replace those three and start from the top half.

The worst-case scenario is all fuses remove and the meter is still showing a drain. This would suggest that the drain is from the fuse panel back to the firewall plug. Separate that plug, if the drain is still there then the source in under the hood.

Hope the how to is understandable and will help you troubleshoot this.
Make sure you close the doors to kill the dome light, ignition switch off pull the key out.

It's a three wire.

Thanks for all the help and suggs.

I recently had an alternator short to ground, it blew the fusible link.

It is equally possible for an alternator to 'leak' to ground.

"It's a three wire" ...ok Mudduck3

Still playing with this....

I found this digram and it shows an external regulator, if the regulator is not working then that could explain the voltage drop at start up. Meaning the regulator is not changing state and you are running off the battery.


http://averagejoerestoration.com/res...rams/1965c.jpg

Something else to notice, there are TWO main disconnects, firewall plugs.

Let's start simple ..........Could this be what is happening to you ?

You charge the battery and take a drive, let's say the battery is not charging, but will power the car long enough for your drive. The next day it is low because the battery is not charging, not draining over night, not charging while driving.

You had the alt checked, it came up good the next item to suspect would be the regulator. Two suggestions, get a regulator 20 bucks or so.

2. Set the multi meter on OHMS and take a reading from pin # 2 from the bottom, reference the diagram to the case or ground, same / same electrically.

It should read some OHMs if it reads nothing or open that is indicating that the coil for the relay is open and failed. Even if the reading comes up right, there is still another problem that could be going on with the regulator and that is old age. The relay contacts themselves may be burnt & pitted enough as to not allow an electrical connection when closed. Hence not allowing the battery to charge.

Good luck keep in touch....

Disconnect negative lead on battery and then hook up a small 12 volt light bulb between negative battery cable and negative battery post (use aligator clips). With car off, the light bulb should be out but your's is probably lit. Start pulling fuses, one at a time, until light goes out. When light goes out, you have found the circuit that is draining your battery. Look at everything on that circuit for the unintentional ground or short.

I replaced the alternator this weekend. The voltage, while running, returned to normal 13.8v. When I get home today I'll check where it's at. Fingers crossed.

New alt. . . still dropped. Changed the regulator . . . still dropped. I think I'm gunna take her out on the back forty and "put 'er down"!! Ha ha!! When I changed out the regulator the contacts look good, but when I looked at the plug contacts they looked kind of old. I'm guessing it's the original harness, where all components are new from rebuild.

I assume by drop you mean after start up ? To help you, please clarify what the problem is. Not charging or draining with the ignition off.

" When I changed out the regulator the contacts look good, but when I looked at the plug contacts they looked kind of old"

Contacts looked good, like not opening and closing, no markings?

On the schematic wire # 35 should have 12 vdc after start up. That will energize that regulator. Disconnect the plug, start the car meter that wire # 35 see what you got.

Or pop the cover and watch the regulator contacts notice if they change state after start up. The regulator is no more then a relay.

You have a generator dash light what is that doing?
This was a working system right, after rebuild?

Sry, by dropping I mean after sitting all night it drops from 12.7 down to 12.15. It still starts up and charges, about 13.8 while running. The contacts on the reg. looked like new, no markings. The reg. is sealed so I can't get the visual but I will do the #35 wire check. I don't know what you mean by generator dash light. It has oil and alt. light but that's it. They both light up nice and bright. Yes, the system worked fine for 4 years. Pop didn't drive it much and it sat for awhile. I ended up switching out the carb due to the Holley gettin gunked up from varnish in the tank. Then a day soon after, the bat. was dead and the saga began. Now I'm lucky enough to have the opportunity to get advice from you guys.

Draining, good now we are talking apples and apples, It sounds like the car is charging, forget the regulator test.



Remember how to hook the meter up to read the battery drain using the AMP scale? The meter needs to be in series with the battery to read AMPs. Someone suggested using a light bulb instead of a meter, that could work, but a meter will tell you how much the drain is in AMPs.

Referring to this digram: http://averagejoerestoration.com/res...rams/1965c.jpg

See the starter relay, look at the post that has the battery wired to it.

Remove the small wires from the started relay. Now attach each wire one at a time and notice what wire causes the meter to give a reading. Tell me how many small wires are there.

There are two # 37 ( BLK- YELL) wires, one from the alternator and the other to the fuse box. The one to the fuse box also feeds the light switch and the ignition. Tell me what you find out and we can pick this back up.

This will tell you where the problem may be, engine compartment or interior, fuse or accessory related. I found a picture of a 65 mustang fuse box and it looks like it only has 5 fuses,. Is that what yours looks like?

Please tell me some more about what is there electrically. glove box cigarette lighter, AC that type of information.

One thing I would surely check is the dimmer switch as it's location can lead to rust and it shorting out.

Originally Posted by NTFDAY

One thing I would surely check is the dimmer switch as it's location can lead to rust and it shorting out.

Ken, another long shot is a cigarette lighter. Had one years back that was stuck "in" part way, creating a bad path direct to ground. Chased that one for a few hours, and could not believe that a $2 lighter element "fixed" my problem!

Originally Posted by rspears

Ken, another long shot is a cigarette lighter. Had one years back that was stuck "in" part way, creating a bad path direct to ground. Chased that one for a few hours, and could not believe that a $2 lighter element "fixed" my problem!

Agree, Roger. In 62 I bought a 40 2dr standard sedan that was draining the battery. I spent the better part of 4 weekends trying to find the culprit. My dad had a Ford mechanic friend come over and the problem was the ignition switch It was worn out and shorting across the terminals. Once replaced, problem solved. I was stationed in San Diego at the time and bus fare to Long Beach, where the car was, was eating me alive.