Parasitic Drain?

[Youngblood]

Hi; I have a 1930, 6 volt positive ground. If I leave the fuse in after shutting off the car, I am experiencing about .2 volt drop in voltage at the battery over about 6 hours. Is that normal?
If not;
Do I need to just start disconnecting wires from the horn, lights etc. to find the drain?

Or, can I check various wires with a clamp amp meter to determine the drain or will all of the wires show an amperage reading if there is a drain?

Thanks for your help.

Mike

[BRENT in 10-uh-C]

Mike, do you have a generator or alternator? Did you disconnect the wire from the alt/gen and see if your draw is eliminated? A self-exciting regulator in the alternator does have a draw.

Yes, just begin eliminating circuits. The original type ignition switch can also see leakage as the ignition coil stays 'hot' all the time.

You can remove a circuit and then use a test light in that circuit to see if there is a draw as it will dimly illuminate if there is a draw downstream.

[Youngblood]

Thanks Brent. Yes, I have an alternator and I checked it. It shows a draw of .9 amps so I believe that would be the reason the battery draws down if I leave power to the system. I will just need to make sure I cut the power to the car when I shut it off for a period of time.

Thanks,
Mike

[Badpuppy]

Originally Posted by Youngblood

Thanks Brent. Yes, I have an alternator and I checked it. It shows a draw of .9 amps so I believe that would be the reason the battery draws down if I leave power to the system. I will just need to make sure I cut the power to the car when I shut it off for a period of time.

Thanks,
Mike

.9 amps is rather a lot. Most likely a rectifier diode has failed (there are three of them, pressed into the finned assembly). Rectifiers are available for not a lot of money, just be sure you get the right polarity.

https://www.ebay.com/itm/10SI-Delco-...3587816?_ul=IL

[Patrick L.]

Originally Posted by Badpuppy

.9 amps is rather a lot. Most likely a rectifier diode has failed (there are three of them, pressed into the finned assembly). Rectifiers are available for not a lot of money, just be sure you get the right polarity.

https://www.ebay.com/itm/10SI-Delco-...3587816?_ul=IL

Thats a draw that should be addressed. And, yep, its an easy fix and parts should be available.

[Ruth]

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If your alternator has a bad diode in the rectifier it will show a draw. You might think about having it checked?

[Patrick L.]

Alternators have a parasitic draw, its just in their nature.

So, a heavy main disconnect switch that is easily accessible may be a good addition.

[Youngblood]

I will do that. Thanks for the help.

Mike

[rotorwrench]

Alternators with a bad diode can have a parasitic draw but a well functioning unit will have no draw at all. It is not in their nature to have a problem like that but it can happen over time with electrical spikes or excessive jumping of a worn out battery. I really can't speak to the reliability of the conversion parts. I only tried an alternator once before going back to a generator on my old 29 Ford. The 10si is very reliable using 12-volt negative ground (normal) components in a 3-wire configuration.

The kits used to convert a Delco 10si to 6-volt have a new diode bridge & regulator plus all the parts to overhaul one of these units. These parts and the polarity jumper are all thats needed in a conversion.

[BRENT in 10-uh-C]

Originally Posted by rotorwrench

Alternators with a bad diode can have a parasitic draw but a well functioning unit will have no draw at all. It is not in their nature to have a problem like that but it can happen over time with electrical spikes or excessive jumping of a worn out battery. I really can't speak to the reliability of the conversion parts. I only tried an alternator once before going back to a generator on my old 29 Ford. The 10si is very reliable using 12-volt negative ground (normal) components in a 3-wire configuration.

The kits used to convert a Delco 10si to 6-volt have a new diode bridge & regulator plus all the parts to overhaul one of these units. These parts and the polarity jumper are all thats needed in a conversion.

Are you sure? I have yet to find a 10si self-exciting regulator that did not have an electric draw, -even brand new out of the box.

[Patrick L.]

Originally Posted by BRENT in 10-uh-C

Are you sure? I have yet to find a 10si self-exciting regulator that did not have an electric draw, -even brand new out of the box.

I better keep my mouth shut.

[Youngblood]

Hi; I called Nu-Rex and asked them about the draw. There is a draw on the alternators. There is always a small draw when the Battery is connected. 1 - 2 amps is not uncommon but they said it should not cause a significant voltage loss at the battery over time.

Mike

[Patrick L.]

Originally Posted by Youngblood

Hi; I called Nu-Rex and asked them about the draw. There is a draw on the alternators. There is always a small draw when the Battery is connected. 1 - 2 amps is not uncommon but they said it should not cause a significant voltage loss at the battery over time.

Mike

Well, Nu-Rex is right. But I think that amount is a bit high, but, regardless they draw.

As mentioned, a good shut-off in a convenient location is a good thing.

[JKY]

Originally Posted by BRENT in 10-uh-C

Are you sure? I have yet to find a 10si self-exciting regulator that did not have an electric draw, -even brand new out of the box.

I would agree. That diode will have a very small leak (draw) even when brand new. When it goes you will see a big draw.

[bbrocksr]

Originally Posted by rotorwrench

Alternators with a bad diode can have a parasitic draw but a well functioning unit will have no draw at all. It is not in their nature to have a problem like that but it can happen over time with electrical spikes or excessive jumping of a worn out battery. I really can't speak to the reliability of the conversion parts. I only tried an alternator once before going back to a generator on my old 29 Ford. The 10si is very reliable using 12-volt negative ground (normal) components in a 3-wire configuration.

The kits used to convert a Delco 10si to 6-volt have a new diode bridge & regulator plus all the parts to overhaul one of these units. These parts and the polarity jumper are all thats needed in a conversion.

I have to disagree with " a well functioning unit will have no draw at all."
A brand new alternator will have a minimal draw.

Diodes do not resist backflow 100% nor do they conduct current 100%.
Bill

P S I hate to agree with Brent but he's right.

[JKY]

Originally Posted by bbrocksr

I have to disagree with " a well functioning unit will have no draw at all."
A brand new alternator will have a minimal draw.

Diodes do not resist backflow 100% nor do they conduct current 100%.
Bill

P S I hate to agree with Brent but he's right.

Yep, he is.

[nkaminar]

This may be unrelated, but it is normal for a battery to loose a little voltage when sitting after being charged.

When I am away from my car for more than a week I will disconnect the battery with the main switch and put a battery maintainer on the battery.

[rotorwrench]

I've worked on many old GM vehicles that had the 10si and repaired dome light switches that showed a current draw but there was never a draw after the repair completion. Now I'm not a fan of the 6-volt conversions so that's why I can't vouch for them. I converted my Ford 850 to 12-volt so I could get the reliability and there has not been a parasitic draw problem with it yet. I use all three wires and a warning light. After I shut it down the ammeter is at zero.

[nkaminar]

I guess one could mount an original style generator cutout on top of the alternator. Once the contacts are open, there is no current flow.

[Tom Wesenberg]

Originally Posted by nkaminar

I guess one could mount an original style generator cutout on top of the alternator. Once the contacts are open, there is no current flow.

There you go, and that should would have a lot of people asking questions!