If I'm correctly following you...
As I posted here I think two days ago, I measured the amperage draw (between the battery's negative post and the disconnected negative battery cable) with everything off plus doors and trunk closed and I read 10 milliamps.

Actually as I had noted previously in this thread, even with the old alternator, I was having the battery-light-on-at-initial-start-up-at-idle problem.

Just to confirm that I'm understanding you correctly:
Are you suggesting that I remove all of the fuses from the fuse box and then test to see if there is any amperage draw between the battery's negative post and the disconnected negative battery cable?

Are you suggesting that if there is still some current being drawn after doing the above test, to then disconnect the alternator and see if that kicks the draw to zero?

To use a double negative, I don't doubt it.

Earlier this year, I had the old alternator tested and the guy testing it confirmed that the alternator was ok (I don't recall what he got as voltage output). However, as I noted previously in this thread, even after replacing the voltage regulator, the alternator was kicking out 13.13 volts the last couple of weeks even after reving the engine. Insufficient output.

Thanks for continuing to offer help with this mystery--

Ten milliamps draw is just the clock probably. Next I would check to make sure the glow relay is really staying off after the cycle. Just make a habit to disable it after starting the car for the next period of time. If that sircuit is intermittently activating it is a known battery drainer. If the problem ceases you know where to look exactly. Also disconnect that glow plug circuit with the car off as well.

I hope you do not have any type of intermittent drain with the car shut down. It would be unlikely but possible. Something is going on though as you say.

The alternator screened clear obviously. Usually a diode will short of course and the problem would have been found fast. It was a long shot but some reverse leakage to a much lesser extent on a diode has been known to occur on rare occasions. This was not your problem. It just seemed coincidental that you changed the alternator out way back. As you said the problem existed with the old alternator as well. I was not sure of that.

Intermittent self triggering glow plug relays are not all that rare either. I suspect you have a heavy unwanted drain when your problem occurs. Since i suspect you have some electrical/electronics experience. If you tapped into the cigarette lighter and monitored your operational voltage by leaving your meter hooked up for awhile. You should notice the voltage drop when the excess load occurs.

I do not suspect you have a static discharge problem when car is not being used. More probable a heavy periodic dynamic drain while underway so heavy that the alternator cannot keep the battery up. If by chance you have a spare glow plug relay I would swap them for a test. At this stage I certainly would not run out and buy a new one. Exception is a used one from a salvage yard for five dollars or so. Everyone should have a spare glow plug relay if cheap enough anyways.

On top of the right fender there is an electrical connector with three screw contacts, the live contact is suppled directly from the battery, and from the alternator when it is running. If the voltage at this contact is different than the volatage at the battery, it will give us a hint where the problem is.

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Quote:

Originally Posted by Craig On top of the right fender there is an electrical connector with three screw contacts, the live contact is suppled directly from the battery, and from the alternator when it is running. If the voltage at this contact is different than the volatage at the battery, it will give us a hint where the problem is.

Ah, right. I know just what you mean. Useful schematic too.

I abhor making assumptions about electricity (probably a good trait!)...So, just so that I'm clear about this:

1. With the engine off, measure the voltage across the battery OR measure the voltage at the three-screw pad at the wire supplied directly by the battery (shouldn’t matter which of these two approaches I use, or...?)

2. With the engine running, measure the voltage at the three-screw pad at the wire supplied by the alternator?

Have I got it right?

Incidentally, there appears to be very little parasitic drain taking place. The vehicle hasn’t been driven since Saturday, the battery is connected to both cables, and the voltage has stayed between 13.30 and 13.32 volts.

I re read the thread. thrteen point two volts after sitting for a few days without running is good and bad. I think a sitting idle battery after a few days should not be this high. I do not know everytthing though. Yet 12.75 volts would seem high normal to me.

I have also re considered your problem. Time to monitor the cigarette lighter voltage. I had assumed everyone had some kind of cord to fit the cigarette lighter socket laying around these days.

By monitoring the voltage while driving something important is going to show up I beleive. The best thing is your car is not impacted with computor related items. So other members will help you get to the bottom of this miserable issue with a little effort by yourself. No fun when a car is considered unreliable and leaves you temporarily stuck from time to time.

Something is telling me you should clean the ground connections from the engine to body and battery to body. Pre emptive if you like. By cleaning I mean get the areas shiny and put some protective grease on the connections before tightning them down again.

Not the problem I think just good items to check on an older car. The mannufacturer never expected these connections to last as many years without cleaning as they have. Or they would have put additional oxidation protection on themselves. Years later some manufactures got the message and did it. In my experience by treating connections I have removed for one reason or another problems never seem to errupt at those points later.

I have just dropped him a PM asking if he could describe and update what eventually was found and the methology used. Adding it to this resurected thread. Well if Whunter returned the thread from the dead why not?

I noticed back then that I was neglectful in my suggestions. . My sure cure that works everytime. Always put comprehensive on a car with a frustrating problem. Torch it and get even more frustrated getting your insurance money. For some terrible reason something in me stops my utilizing it. Call it a major character defect.

I concur, but I would use a proper multimeter and read the current draw through the ammeter setting on the meter. Record each one. Report back.

__________________
Current Diesels:
1981 240D (73K)
1982 300CD (169k)
1985 190D (169k)
1991 350SD (116k)
1991 350SD (206k)
1991 300D (228k)
2008 ML320 CDI (199k)
1996 Dodge Ram CTD (442k)
1996 Dodge Ram CTD (267k)

Past Diesels:
1983 300D (228K), 1985 300D (233K), 1993 300D 2.5T (338k), 1993 300SD (291k)