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Old 08-05-2019, 12:49 PM   #1
Prairie Viking
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Default Parasitic draw from Generator?

Hi all!
I've got a 1950 sedan with V8. The battery won't hold a charge overnight. When I disconnect the battery, I get a spark, indicating a draw somewhere. when I disconnected the Armature lead on the the generator, I got a spark also.
The ammeter shows charging when the engine is running. I ran the generator as a motor by connecting the A and F terminals and running a hot lead to the A terminal. It turned over fine, although a little slow, i thought.
So, I wouldn't think it normal to have a spark when disconnecting the Armature lead. When I leave the armature lead disconnected, I get no more sparks when i disconnect the battery, so is the generator at fault?
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Old 08-05-2019, 12:59 PM   #2
Mart
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Default Re: Parasitic draw from Generator?

No. The regulator is not releasing.
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Old 08-05-2019, 01:05 PM   #3
tubman
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Default Re: Parasitic draw from Generator?

Yep. Had the same problem with my '51. Replacing the regulator solved it.
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Old 08-05-2019, 01:09 PM   #4
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Default Re: Parasitic draw from Generator?

There is a spring that holds the contacts open. You can adjust it so it has more tension to ensure the contacts open. You normally adjust it by bending the tang that the spring is attached to.

I had the opposite problem on my 41 pickup. The contacts didn't want to close. I adjusted the spring looser and introduced the problem described by Prairie Viking. I readjusted until the tension was enough to just open the contacts.

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Old 08-05-2019, 01:20 PM   #5
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Default Re: Parasitic draw from Generator?

There are three relays in the common voltage regulator. First one controls the voltage by opening the field coil circuit when the desired voltage is obtained. Second opens the field coil circuit if the current output exceeds the max. Third is the cut out. This opens the generator out put circuit when the engine is shut off. The first two carry only a small control circuit. The cut out carries the full generator current. This is a heavy load and this set of points is subject to damage by that current. It sounds like the contacts might have welded closed. They'll never be the same if you try separating and cleaning them so a new regulator would be required most likely.
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Old 08-05-2019, 10:04 PM   #6
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Default Re: Parasitic draw from Generator?

OK, so I pulled the cover off the regulator, and sure enough, the cut out points were closed. They weren't welded together and I was able to separate them. I started the car, and ran it a while. While the car was running, the points were closed, but when I turned it off, they opened. When I disconnected the battery, no spark! So, problem solved? I will get a new regulator on order, just in case this one keeps acting up. Thanks for the help guys!
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Old 08-05-2019, 10:25 PM   #7
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Default Re: Parasitic draw from Generator?

in beautiful montana you should not have a moisture problem,but sometimes a little corrosion on the contacts can make them sticky. try just cleaning them up with some fine sand paper and a shot of air or spray stuff like brake clean or starting fluid
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Old 08-06-2019, 05:17 AM   #8
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Default Re: Parasitic draw from Generator?

Quote:
Originally Posted by cas3 View Post
in beautiful montana you should not have a moisture problem,but sometimes a little corrosion on the contacts can make them sticky. try just cleaning them up with some fine sand paper and a shot of air or spray stuff like brake clean or starting fluid
Trying to clean contacts with any kind of sand paper will leave an abrasive residue that will lead to problems. If you do anything like that, use a file. Point files used to be in every mechanic's tool box but that's only a stop gap fix.
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Old 08-06-2019, 08:05 PM   #9
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Default Re: Parasitic draw from Generator?

"When I disconnect the battery, I get a spark, indicating a draw somewhere."

Correct me if I'm wrong but if you tap one of your leads and get a battery spark, it does not indicate a short. With everything turned off, take a amp meter and put it between the battery lead and the battery. if there are amps being discharged, then you have a short.


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Old 08-06-2019, 08:08 PM   #10
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Default Re: Parasitic draw from Generator?

A battery lead spark would indicate a path to ground unless it was just discharging a capacitor somewhere (not likely) and then it would be a one time event. So, yes, a spark at a battery lead being taped to a battery terminal tells you something in the system is drawing current.
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Old 08-06-2019, 08:11 PM   #11
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Default Re: Parasitic draw from Generator?

Model A's and early flatheads work as a "live" system. The systems has current at all time. (less you use a battery shut off). If you take a battery charger and tap the lines together you always get a spark. Best way to read a spark/short is with a meter.


If I take a battery on the bench with 2 leads +/-. I'll get a spark almost every time I connect the leads... here again, I always wondered if there was truth to this tale.

Last edited by Tinker; 08-06-2019 at 08:22 PM.
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Old 08-06-2019, 08:21 PM   #12
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Default Re: Parasitic draw from Generator?

Quote:
Originally Posted by Tinker View Post
Model A's and early flatheads work as a "live" system. The systems has current at all time. (less you use a battery shut off).
Not sure what that has to do with anything, we are talking current flow. And yes the system is "hot" all the time except for what is connected through the ignition switch. That is mainly the coil and instrument panel gauges. The lighting switch is "hot" but only the brake circuit is connected with the switch in the off position. Different years are wired a little differently, but similar. Now, back to the battery lead question, a spark indicates current flow and there should not be any current flow.
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Old 08-06-2019, 08:25 PM   #13
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Default Re: Parasitic draw from Generator?

There is though, as you said. "hot system". Leads complete the system. Take a wrench and put it crossed both battery posts. sparks


Not sure how the short plays into the spark. I don't know?
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Old 08-06-2019, 08:49 PM   #14
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Default Re: Parasitic draw from Generator?

Tinker, not sure what the hell you are getting at with your posts which are not really helpful at all. The problem here was the cut out contacts which were stuck closed and this has been covered in an earlier post. When answering electrical questions then it is only helpful to someone asking the question if you really know what you are talking about. Sorry to be so critical of your knowledge here but incorrect information is only confusing to others. Regards, Kevin.
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Old 08-06-2019, 09:02 PM   #15
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Default Re: Parasitic draw from Generator?

Agreed. So how does a short create a spark at the battery (not at the regular)? When I can create a spark by just crossing leads?


The original question is answered and not related to the battery spark issue... so I don't think I'm messing with any of their problems.

Last edited by Tinker; 08-06-2019 at 09:21 PM.
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