It's winter now, and I need some kind of project to work on now, so I figure I should try and figure out what is causing the batteries to go bad the 300CD. I sort of want to get it back on the road again.

Does anyone know where I should start, I had the alternator check last spring, and was told that it was good. I am going to guess that maybe it has a bad ground strap or something like that, but still don't really know where to start...

Hi Eric , if you have a DMM you can disconnect the battery ground and hook up the DMM between the negative post and ground (with the DMM set on amps) .Normally you will see the clock pulsing between 0 amps and 0.3 amps (I think , it's been awhile). If you have more drain than this , pull the clock fuse and see what you have. Keep pulling fuses and checking till you find the circuit that's causing the drain. It could be something simple like a burnt litebulb that is shorting to ground . Good luck.

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123C,

Its not a bad ground strip. That would decrease any current discharging the battery, not promote current flow.

Do the tests in the above post and you should find the circuit that is discharging the battery.

If you don't have an ammeter, use a volt meter in series with the battery. If the circuit is open, you will read zero volts. Any voltage reading means there is some current flowing in the circuit but you won't know how much like you would with an ammeter.

P E H

Ok, I will try the above sugested method. I am just tired of my batteries going bad all the time, I'm on my 4th one in the past 3 years...

123c,

Were the batteries under warranty? What make battery? Consensus here is that Exide are no good. I had a few of them fail myself. I use Autozone or Walmart batteries now.

P E H

I stay away from excide, it's an industrial battery, and it's supposed to be better than Interstate. I can't remember off hand who made it. It is still under warranty, and they will have to honor it because it has a sealed top...

I've havn't done the above tests above yet, but I have come to the conclusion that I have such a short commute (less than 5 miles) and I don't really ever give my car a chance to get a full charge on my battery. I've been just throughing my battery charger on every night after I get home from work, until it shows a full charge.

My current battery was ok, just way low, and my battery charger wasn't strong enough to get a good charge on it. I took it back to the battery place, and they charged it, and it was putting out over 1000 cca...

I will probally check for a short on my next day off, and hopfully fix any problems that are causing any possible shorts...

I took my car in today, and the tech told me that I do have a major draw somewhere. Now I am going to take up the task of figuring out where it is coming from. I pulled both fuse 2 and C, but it didn't seem to make a difference, so does this mean that the draw is coming from a non-fused source? Maybe tomorrow I will try pulling the fuses again and check them again...
I put a battery disconect swith on the battery, so I can disconnect it when it is parked, so the battery won't go dead... I don't care if the clock is off...

Hello Nucking Futs
I am Cracking Up, great name, and good sense of humor.
Check wires running up your hood hinge, had a MB in Friday for second battery in a month, grabbed the hinge to stand up the hood and burned my hand.
My luck; find the short by hand. LOL...
Where do you park the car?
Monday of last week; had a 500 MB the owner parked under a tree, towed in, charged the battery, location right front of windshield, heard sizzling under battery, pulled battery and tray, squirrels had eaten insulation off five wires, cleaned the nest out, repaired wires, no more drain + the washer works now.

Oh, trunk lights are common cause also.
Hope you find the problem soon.
Have a great day.

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I'll make sure to check the trunk light, maybe tomorrow night if I get the time...

I traced the draw to the dreaded A/C Servo. I disconnected the wires going to it, and hooked the test light to them, and I found that the purple one was lighting the test light. So this probally means that my A/C Servo is bad, or there is a problem further up the line, probally somewhere maybe in the control amp??? I am hoping it's not the a/c servo, since it somewhat works, and only has some minor leaks...

I also found a minor draw coming from the front roof light, but I fixed that problem...