I am wondering if you have a ground issue? Have you removed the ground cable from the battery to the chassis and cleaned the contact? How does your positive battery cable look? They tend to swell with corrosion over time, its also possible to have broken strands of copper near the battery clamp. Did you take the battery in for a charge and testing after you replaced the alternator? I drove my 300d for over a month with the alternator not charging the battery....it seems strange that you can't go a mile before its dead...its also possible the starter could be causing the drain...

Thanks, I had that thought in the back of my head at one point, but forgot it later. Consider this video I just made though, I think it suggests the switches inside the ignition are working properly.

DIAGNOSTIC VIDEO, PLEASE WATCH
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Damn car won't charge - YouTube

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DIAGNOSTIC VIDEO, PLEASE WATCH


I can get the lights in the dash to illuminate if I provide ground to the blue wire at the alt.

The battery is brand new, I charged it overnight after the short in the bad alternator drained it out. Now that I've replaced the alternator, the new battery is holding charge overnight. So that's great. The cables are in OK condition, obviously not brand new, but they're tight and unbroken. If I had a grounding issue, wouldn't I have read something more than 0.01 OHM load somewhere in my testing between chassis, engine and negative terminal? I guess I haven't tested from the pos terminal to the starter, but it's starting just fine as long as there's juice in the battery.

http://www.peachparts.com/shopforum/diesel-discussion/341558-83-300sd-electrical-issue.html

I'm going through similar issues...

That electrical plug for the alternator is pretty dirty. I would pop it open, make a note of the orientation of the wires, clean them really well with electrical cleaner...make sure they are nice and shiny, re tension the wire connectors and confirm all the solder joints are good. Its possible the plug is staying taught in the alternator, but the individual plugs aren't making contact.

Had no clue it came apart. I mean, I looked at it, but couldn't see that it had a split anywhere. I'll give that a try, thanks! Perhaps hooking it up gingerly without the plastics of the plug itself might give insight.

After watching your video, I'm leaning towards cooljay's idea. I might also be having a touch of the same thing with my connector.

It's cleanin' time!

It's also been pointed out to me that the voltage regulator can be damaged by connecting and disconnecting the circuit while the engine is running. YMMV

Just got done taking it apart, it wasn't too cruddy inside, but it wasn't great either. I need to replace the plastics now, and it wouldn't hurt to crimp on some new connectors as the insulation is damaged a bit. I was able to hook up the leads without the plastics in the way to ensure good contact and test. Unfortunately the warning lights still aren't coming on. Curiously I'm reading 2vdc on the blue wire at the alt with the key off and the blue wire lead connected to it's respective home on the alternator. I'm guessing that's going to drain my battery overnight. I'm also guessing this newly installed alternator is already fried. You'd think buying the Duralast Gold (which has a lifetime warranty) would have resulted in an alternator that was going to last at minimum 50 miles. Although perhaps my car is doing something specifically to kill them?

I am running out of ideas. The only other thing I would suggest, is to pull the fuse box cover and check all the fuses...remove each fuse and inspect the ends...Reading a lot of threads on the matter, they say it is possible to have a fuse melt inside. I would also pull the cluster and clean the bundle of grounds behind it, and do a visual inspection of the cluster. All the gauges connect together and that is how they are grounded, by touching one another.....I would also clean and check the wires on the starter...I suppose its possible to have a bad solenoid and that cause your issues, my starter went bad and killed my battery.

To see if you have a bad ground connection on the block/alternator. You can take the negative side of a jumper cable, clip it on the negative side of the battery then the other end to the engine block or alternator.

I read a thread where the glow plug relay can also be blamed, you can pop it open.....remove the connectors then see if your battery light comes back on.

I would think the fact that the Battery Light and Brake Light not working at the same time would have some meaning - like the driver's side front window and passenger side rear window circuit diagnostic.

My new good alt wouldnt charge so I ran a 10 gauge wire from the alt housing to where the neg battery cable bolts to the chassis. Alt gives 13.3 amps now. A simple fix to try

even the best batteries BRAND NEW will be junk if they are discharged to zero. automotive batteries are NOT designed to be pulled below 60% charge. if they are, they WILL be damaged. if completely discharged, special procedures have to be followed to recharge and desulfate the plates... not something most of us have the equipment to do.

take the new battery back to the store and have it tested. replace if it's partially low on CCA.

it's also possible that whatever killed your first alternator is still causing problems.

When you turn the key on, the diodes within the alternator provides the path to ground to turn the charge light on . You said you were able to turn the light on by grounding the blue wire after removing the connector.

Possible causes:

1. Alternator diodes blown open circuit (all 9 of them).

2. Connector not making good contact.

3. Alternator not grounded well.

4. Cluster traces damaged. This can happen if the ground strap on the bell housing is not making good contact while you start the engine.

"Alternator makes a rhythmic rattly banging noise during operation (only with wires connected)"

This is a weird one and raises a red flag. Did this happen with the new alternator? Did you find the cause?

Where are the diodes located and how can I test them? That round black thing on the regulator, or the separate black box? Or elsewhere perhaps.