Battery Woes...

[cooljjay]

This may be of help to others so I am just posting my fyi and I want to hear others fyi's...

I rebuilt my alternator in the 78...the reason was I woke up to a dead battery.

At the same time the evil acc started acting up again. No center vents and heat all the time....AGAIN! I also don't see/hear the servo parking.

The voltage regulator and alternator were very worn so I dedicated the issues with the dead battery is from the alternator.

I purchased a walmart battery that has been on the shelf since June 2014...the others were going on being there for 2 years (No preaching you shouldn't buy a walmart battery Small town less options PLUS my buddy has a 10% discount card and I walked out with a 900cca battery for 125$ )

I stuck the new battery in the car and I put the vom on the battery. 14.1v wooo hooo...I thought!

Well I soon notice the charge dropped down to 13.2 and at ideal I was getting maybe 12.5v

I wanted to say the alternator was/is just to worn down and I needed a new one.

Researching showed that the original alternators and regulators produced lower voltage then the new rebuilt ones with Chinese voltage regulators in order to trickle charge the battery so it will extend its life time.

I concluded everything was ok because this differents could be deducted to a 55amp alternator. There is also very little info on here about 55amp alternators and voltages.

I compared the 78 to my 82 euro. My euro always charges at 14.1v and only reads 12.3v if the care is off and radio playing. Idling I always see 13.8v at the minimum. I concluded the differences was because this is a "lifetime" 65amp alternator.

Fast forward to today. My buddy went to start the 78 and he said it was dead! I was UGH!! I went out and put the vom on the battery 10.3v I hadn't driven the 78 for about 3 days. This is why I thought it may be a evil ACC drain issue. Remember everyone sites that as the main issues with the ACC.

Okay I had it! I then pulled the battery from the euro/82 and switched it over as I knew the charging system is fine on the 82. I then put the new walmart battery in the 82.

As soon as I started up the 78 it idled at 14.1v With brights on and everything it only drops to 13.5v.

I then got the walmart battery hooked up into the 82. It took a long time to get to 12.5v idling. I then deiced to go for a drive to charge the battery as I have done in the past.

A 100 miles of driving of 80mph+ hwy driving I only was getting 13.5v

I let the 82 idle in the drive and when I came back out it was reading 13.9v idling.

I know the evil acc needs to be gone over and "see" what blew now but I had checked for voltage drain before and it would only maybe go down a 1/2v every 2 days. Also when I put the 82/euro battery in I checked it unplugged and then replugged in..I had no voltage change...

At this point I am saying that it is 95% the battery. I know there is nothing in the euro/82 that will drain the battery and everything is manual the only strain I put on the alternator is with the radio. I also have a voltage gauge wired and applied to the dash. I will be keeping an eye on this battery, if I don't get it to max at 14.1v it will be going back and I will get one from Napa.

My FYI for everyone is; Don't go after a walmart battery, DEMAND the battery be charged and tested, and wire in a voltage gauge they are very cheap and easy to install.



At this moment I have concluded that is the battery is bad or it was near drained when I got it. With all the electric doo dads on the 78 the alternator just couldn't throw out enough voltage to charge the battery, run headlights, climate control, radio and windows.

After I installed the battery and alternator in the 78(thread on rebuild on site below or here in my threads) I went for a long test drive. Even that freeway drive with no accessories on only maxed my charge at 13.8v.

I must recommend anyone running a 55amp alternator upgrade to the 65amp they used on second gen w123's. It is just not powerful enough to run all the electronic stuff on the early models with very little driving.

I will update with any further learning I might make...

[TnBob]

Insane as it sounds, make sure your glove box light is going out, that the door is actually turning the light off.

Interstate Battery... blems. Ive gotten 3 group 48's for 300D and 300SD for ~$40 installed.

Liberty Auto; Inc.
59 7th Ave
Page
AZ
86040
(928) 645-3848
Best chance in stock

or...... http://www.interstatebatteries.com/DealerLocator/Default.aspx

[mespe]

I'm willing to bet that Walmart battery is just fine. What you are experiencing is typically corrosion in the battery cable. Usually near the positive clamp the wire itself starts turning green. electricity flows on on the outside of the copper strands and any green adds resistance to the wire. So what you got is a voltage drop between the battery and all devices connected to the battery. You will need to peel back some of the cables insulation until you see bright red copper. Use baking soda, coca cola, ketchup etc to clean the green off, then wash and rinse and oil it up to keep it from corroding anymore.
Alternatively, It could also be the ground strap from the engine block to the chassis as those corrode as well. Either way, corrosion is your problem and will probably help the ACC out too.
Good luck

[ah-kay]

You have a drain somewhere. I cannot imagine any car would require 55Ax12V = 660W all the time. Unless, you have a 1000W amp in the car blasting away. Nominal voltage on the car battery is 12V. When idling, any, I meant, any voltage over 12v would charge the battery. I really cannot see any issues with the battery from Walmart, or from anywhere else.

[Zacharias]

The advice others have offered is sound. I agree the battery is unlikely to be the usual suspect here.

I went through something very similar over more than a year and was at wits end before it became clear it was a faulty diode in the alternator.

Along the way I put the touch on Wal-Mart for a replacement for a one-year-old battery. My mindset during the problem-solving was probably pretty close to yours.

I agree on the voltage meter and the alternator upgrade. I use a plug-in to the cigarette lighter myself and when I bought a new alternator I went to 75? amp. Maybe 65, it was such a thrilling blur... not. Try finding an alternator on new year's eve.

[cooljjay]

Thanks guys!

I have brand new custom made 2 gauge battery cables about 2 years old on that car and well shhhh over the counter ones on the euro.

No Mercedes diesel should be with out 2 gauge cables with both ends molded on!



Good point out on the ground cable! Already done!

So far I got the walmart battery to charge at 14v and 13.7 with H4's on and radio. I believe as is said it is good!

I checked the 78 and it is still holding at 12.5v but I didn't start it. My buddy is attempting to take it to work again tomorrow. When he gets back I will see what it is charging at.

[cooljjay]

Here's a little update and another cool po folk test tool!!

I have been racking my head onto what is causing the drain, the diodes in the alternator all tested fine granted the numbers were -/+10% but they were okay and I couldn't see any easy way to replace them.

I was thinking my radio is causing the drain as the memory started working even weeks with no battery in the car, my presets were fine!

Then I was is it the antenna?

I knew the CC aka evil ACC stopped parking...as I couldn't hear it any longer center vents weren't working and heat wasn't going off.

If you're not familiar with the system there are two fuses one in the fuse box, that is for the compressor etc and another inline next to the ice cube relays.

I just pulled these the other day till I could diagnose it.

Today the car is home so it is time to diagnose, as my luck would have my VOM doesn't have low amp setting on it. Then it was time for a test light, which I don't have...


Apologizes for bad photos...I didn't have my good camera and well like all my electronics seems to be having issues..thank you Japaneses junk!

Guess what doubles as a test light? A dome light!!


As I guessed it the alternator is fine but when the fuse even just the ac compressor fuse inserted it glowed extremely bright!! When the inline fuse was installed it dimmed a bit.



I decided to remove the evil ACC computer. It is a newer one but look what I discovered...a few traces on the board aren't covered in solder...someone at the factory was skimping...not sure if that is the issue but it appears to be an issue. I have to pull out the schematics and all that crap to diagnose the system again.


Good thing is, I have a buddy down the street with an 80 wagon who upgraded to the unwired kit! He said he would give me his servo and computer for spares.