1982 300TD battery drain issue - PeachParts Mercedes-Benz Forum

Goldie · #1 05-08-2007, 08:31 PM

Greeting Benz friends. I have had the unfortunate experience (twice) of getting in my 1982 300TD having put a fresh battery in after the winter to find that there is no charge on the battery - nothing. No lights when I turn the key, etc. I did remove the radio recently and I have not installed the new one. Are the dangling wires the culprit? When I put in the new battery, both times, she started right up. There was about a week between attempts each time. Luckily the outfit that I bought the battery from was kind enough to replace it (I think there was a year warranty on it.) Not sure if they'll do it again.

Thanks for your insight.

I did read the post below and some others.
Is it the Battery or the alternator??

It seems like the connects are in good shape. I sprayed them with terminal protector. But the battery is definitely dead. I tested it with a meter and tested the meter on another battery just to make sure.

Quote:

Originally Posted by Mike D

1st step. Check battery cables.
2nd step. Clean and tighten battery cables.
3rd step. Check ground connections and cable feed to starter.
4th step. NOW begin to diagnose.

Alternator belt tight or worn out?

Usually the red charge light will come on if it's an alternator or belt related failure.

90% of all non-start or non-charge conditions are cable related.

Many, many times I have seen a perfectly good battery replaced and the owner thinks the problem was solved because the car starts now. Of course it does! When they replaced the battery they had to clean and tighten the cables on the new battery.

Eliminate the obvious.

When you have the car running put a voltmeter on the battery posts. If it reads above 12 volts the alternator is charging. As the battery receives a charge the voltage will increase to about 14.0 volts.

SD Blue · #2 05-08-2007, 11:32 PM

It sounds like you have something drawing it down. You will need to place an amp meter in series (start on highest setting) with one of the battery cables then pull one fuse at a time to isolate.

vstech · #3 05-09-2007, 08:54 AM

if you don't have an amp meter, what I did, was in a darkened room, with a good battery, disconnect the neg, and tap it to the neg terminal. there should be a slight or a strong spark. now, start removing fuses one at a time until the spark is gone. then figure out what is on that fuse and start eliminating them until you find the spark maker.
John

SD Blue · #4 05-09-2007, 11:12 AM

The "spark" method is NOT A GOOD IDEA! It will work unless the battery blows up in your face, then a drain will be the least of your worries. Batteries give off hydrogen gas (think Hindenburg) and sparks in that area should be avoided.

Goldie · #5 06-26-2007, 10:40 PM

I'm back after a brief hiatus. With a second set of eyes on the problem, I found that there is indeed a draw on my battery. I was trying to jump it today (I know, I know - I need to get my hands on a charger) and while we were waiting for a charge I was in the cabin poking around and trying to figure out the radio wiring (which we did!) What I found was that the lights for the AC control unit on the console were on! (and an obvious culprit for drawing my battery down.)

We took out the fuse for the overhead lights, etc. that the AC controls are on. Unfortunately, the battery never did get enough juice from jumping it so I couldn't get the car started, but I am a lot closer now than I was.

Now I need to figure out why those lights were on. According to the shop manual are connected to the light switch with is hot at all times, which connected to the instrument cluster (more on that in a minute), which is connected to the fiber optic connection (how does this thing work?), which is finally connected to the AC controls in the center console.

Is there something wrong with my light switch? I had to do some work on the instrument cluster and I re-grounded it because it was acting up. Is it possible to do this incorrectly? Any other thoughts?

Thanks again!

I have the wiring diagrams and introduction for anyone who is interested.

1982 300TD "Goldie"

vstech · #6 06-26-2007, 10:51 PM

is "goldie" a wagon? a 123 300TD yes? I did not know they had fiberoptics in them. I thought the 123 was all bulbs.
you should be able to get a simple charger for around 20.00 the battery should be under warranty, most of the group 49 batts I have seen have at least a 3 year warranty free replacement! go get a new battery, and a small charger, and hook them up. find the drain. if it's your dash lights, make sure your light switch is indeed in the off position, that's straight up. if you go all the way to the stop, you will have your parking light on.
if you don't find the drain, get a battery disconnect switch, or do what I do, and just leave the neg terminal loose, and remove it when you park. good luck.

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