Inliners International
Posted By: cruisin'64 Parasitic Drain. What to fix? - 07/22/14 12:20 PM
Having a bit of an issue with the starting/charging system in the 64. Motor is a 250, mild upgrades.

From what I can tell of the car, the charging system (minus the battery) look to be 100% original. Car has an alternator instead of the generator, but from my searching this was the first year where alts were standard.

Before now, if the car sits for a day or two, the battery does not have enough juice to crank the motor. It clicks once or twice and requires a few turns from the start to on position before it will spin the starter. It will usually start right up at this point.

The other day after a long cruise, I parked the car in the garage and the GEN light stayed illuminated. Concerned, I looked around the engine bay for a shorting wire, but didn't find anything. I unhooked the pos battery post, and the light went off. Put it back on, and the light stays on. I unplugged the alternator (two wires leading to harness, etc) and the light goes off, but the dome light stays on. After driving it for 20 minutes to charge the battery, I parked it again and removed the pos terminal and let the car sit for a few days. Put the terminal back on and no juice for starting.

Should I start with the battery? It has a stamped date of 2006 on it. What other tests should I do to test for failed parts?
Posted By: Mitch Re: Parasitic Drain. What to fix? - 07/23/14 12:14 AM
I would replace the battery, the lucky batteries make it 8 years but that's not the majority. Most are at 6 if they are a quality brand. I don't think that'll necessarily solve your problem either, but it's probably needed.

Did cars with alternators have Generator lights? Seems backwards to me but also seems entirely possible.

To find a draw, I pull the negative battery cable and put a test light between it and the negative post on the battery. The test light will light up if you have a draw. Next, start pulling fuses until the light goes out. Once it does, then you know what circuit is drawing (whatever the fuse is labeled). Go from there and find the fault. Sometimes there is only 1 thing on the circuit, sometimes there is more.
Posted By: intergrated j 78 Re: Parasitic Drain. What to fix? - 07/23/14 08:49 PM
When you pull the neg batt cable and use a test light make sure the doors are closed or the dome light fuse or bulb is pulled, otherwise you think that you have a draw down when you don't. Another thing that will trick you is a factory clock. They use a pulse to wind them every so often. On a 64 chevy if the key is in the acc position the "gen" light will glow dimly. It could also be the voltage regulator. I agree with Mitch that battery has to go, still check for a draw though. Please let us know what the tests show, I love electrical work and will help anyway that I can Jay 6155
Posted By: cruisin'64 Re: Parasitic Drain. What to fix? - 09/23/14 11:24 AM
Ended up replacing the volt regulator and the battery. No more drain!

Although I did notice that when I remove the pos cable from the battery while the engine is running, the car stops. Am i wrong in thinking that the car should keep running off the alt? Or is the battery part of the charging system, and without a connection to the batt, this line is broken?

I was always under the assumption the alt runs the car while the engine is on.
Some alternators have a threshold RPM, below which they do not charge. If you were idling it may not have been putting out.
Posted By: cruisin'64 Re: Parasitic Drain. What to fix? - 09/25/14 11:16 AM
Hmmm, interesting. Any way to find out if my alt is one of these types? It's a factory / OEM replacement, looks like a core. Has the Delco-Remy stamp.
Posted By: stock49 Re: Parasitic Drain. What to fix? - 09/27/14 12:28 AM
Originally Posted By: cruisin'64
I was always under the assumption the alt runs the car while the engine is on.


If the alternator is a three-diode design then once spinning it is self sustaining. I have read of early alternator designs where the Field Current source is solely the battery. Remove it from the circuit and the alternator ceases to produce power. Same is true for a truly dead battery (versus just a drained one). Jump the vehicle - up and running. Remove the booster cables and the engine dies . . .

Here's a link to an article that describes a three diode alternator circuit including how to interpret the warning light (dim/bright) . . .
Understanding Alternators
Posted By: cruisin'64 Re: Parasitic Drain. What to fix? - 09/29/14 12:59 PM
That's a great resource - thank you!
Posted By: intergrated j 78 Re: Parasitic Drain. What to fix? - 09/30/14 08:08 PM
Glad to hear it is fixed! The stock alt for a 64 Chevy is a 10 dn and puts out 37 amps if the car did not come with A/C. It does not use a diode trio and has a separate volTage regulator. We used to change the way the stator is wound and double the output. Jay 6155
Posted By: GMDad Re: Parasitic Drain. What to fix? - 01/15/15 10:11 AM
You could install a 72 and later alt with an internal reg with a higher amp output.
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