Parasitic battery drain

[h20rider]

After installing a newly rebuild engine, I’ve discovered a battery drain that depleted a new battery overnight.
In trying to track it down, I have done the following with these results:
- verified drain by disconnecting neg batt lead and checking for voltage from cable to neg. terminal. Reading 0.15 volts
- disconnected alternator and ignition from post term. Tested negative cable to neg. terminal on battery. 0.06 V (60mv)
With starter and ignition attached but alternator disconnected (both B+ and ground) same results…. 0.06 V

Battery charged at 12.5 volts
- engine running charging at 13.6 volts
- removed all fuses one by one…..drain continues at 0.15 volts (eng. off)
- Neg batt terminal to alternator body = 0.2 V (eng. off)
- Pos batt terminal to alternator ground connection = 0.38 volts (eng. off)

The cables for the starter, the ignition, and alternator all seem fine.
Just to be thorough I checked continuity from the disconnected D+ cable end to the disconnected cable end at the pos. Batt terminal. My multimeter would nor read it, but using an LED test light with a small 9v battery, I got light…dim but there.

I suspect the alternator is the problem, but before shelling out for a new one, I am hoping to get opinions from the members.

BTW, a couple of years ago, I installed a new wiring loom…so the the wires are in good shape. I’ve double checked as many connections and grounds that I can….with no apparent shorts. Also since the fuse removals don’t change the drain problem, I am assuming the problem is hidden in the charging circuit.
Before I pop for a new alternator…..do I seem to be missing anything? Other diagnostic I should run?

73 KG with 1776 engine msg ignition
Also, the car runs fine and the dash meter shows good charging

Thanks

[74 Thing]

Google "msd ignition drain battery"-I would start there.

[Dale M.]

[h20rider]

More info:
I started the car and it showed good charging.
Then, I tested across the battery terminals for ac current. None

Next, with engine off, I disconnected the MSD ground at the battery. Then, I checked for spark when either moving into the negative terminal or getting right up to a ground source on the body.. no spark, but multimeter read 25 me when tested from MSD ground wire to the negative battery terminal.
So, the MSD with no measurable amps. That is a lot better than the 150-200 mv drain determined by testing from the battery ground cable to the neg. terminal.

If I get a hold of a different alternator and put the B+ and D+ leads on ir, I assume that substitution could solve the question as to if the old alternator is faulty.
Thoughts?

[modok]

If you think the alternator is the drain then...... why don't you check the amps in the wire between the battery and alternator?

I assume your "25 Me" and 200 Mv...... is Ma, mili amps? probably
auto-correct?

So maybe 200 Ma is your total drain. Bit high probably.

Testing between the alternator and battery+ should show how much of that drain is from the alternator.

[74 Thing]

Yeah, you wrote that you removed all of the fuses in the fuse block and there is still a drain.

What is left hooked up to the battery (MSD, starter, alternator and wire to headlight switch). Disconnect one of those at a time and see what happens.

[h20rider]

Duhhhh….okay, I have been a bit of a doofus. I was measuring voltage, NOT amps! The “mv”s were millivolts.
Earlier today, after getting rid of some unnecessary circuits, I left my battery installed but without a tender. It was fully charged so I will check again in the morning. I will also redo the test from ground lead to neg. Terminal….but on the amp scale.
In the meantime, I will hide my head in shame.

[bsairhead]

You will figure it out. There is nothing wrong with your method once you set your meter correctly. I do drain troubleshooting with an analog OHM meter. I take the battery out of the loop buy disconnecting the neg just because it's easier but it makes no difference. You don't even need a battery with my method. Attach a lead to the + side of the battery or the fuse box tab supplying the fuse box. #9 I think on your Ghia and the other lead touch to ground if the needle moves you have a closed circuit. Double check all dash switches door switches dome light (if you have a bus) and aftermarket stereo hot and ignition switch. Pull that supply fuse first. If the meter does not show closed (movement) some one has tapped into the non fused + wire. If the meter shows open as it should pull the fuses (one at a time) that are bussed to that fuse (my 71 bus has two) that will determine which direction to go. I like this method as it is not hot. Once you find a fuse that when pulled shows open (no needle movement) trace that circuit. Easy right

[Zed999]

When I had similar, it was a faulty ignition switch. The giveaway was being lazy I'd sometimes switch off the engine with the wipers running. They'd stop of course as they are ignition on fused and the ignition should cut off the supply to those fuses... but later I'd find them running!

[kamshaft91]

Did you change from generator to alternator?
If so, I had the same issue many years ago (10ish years or so) you did and found it was from the alternator. I had to install an in line resistor on the B+ wire to stop it. When I get home I’ll take a look and see what it was exactly and report back.

[h20rider]

Well, even though I made a rookie mistake….cleaning up my wiring, getting rid of unnecessary circuits (seat heaters, extra lights, ) seems to have solved the problem. Thank you everyone!!