My 1984 300D is Freakin Possessed. - PeachParts Mercedes-Benz Forum

renman · #1 08-06-2008, 11:52 PM

I have posted a number of times regarding electrical problems related to battery drain with my car.I have read and followed many related posts on this forum regarding battery drain. All for naught. I am very frustrated. In the last year I have replaced the battery, upgraded to a new saab alternator, replaced cables, cleaned connections, found and repaired dead shorts, replaced the glow plug, checked all the fuses to see if there was a drain while the car was sitting,replaced the glow plug relay,had the battery and alternator tested at (3) three independent service shops twice, and just recently installed a kill switch under the dash which makes the automobile electrical system completely dead after I turn the car off. This car continues to drain the battery.

On the way to town this evening my wife had the battery go dead after she had driven 35 miles, and stopped to get a bite to eat with my daughter. She finally got a jump and headed for home but; here is the weird thing; for about 30 miles she drove with very,very dim lights in the dark. In the last five miles, she said the lights just "came on" and brightened to normal intensity so she could see to drive safely. Go figure.

So my car can't be discharging while it sitting now,but man doe's it keep chewing the battery up. About the only thing I haven't replaced is my starter, which did fall out of the car last year. Really, it just fell off of the engine. I bolted it back up to the block, and it doe's fires the engine right away but I wonder if the starter could have been damaged or was on its way out since the car was having discharge problems even back before the starter fell out. With a charged battery the engine fires instantly.

I feel like this is a war of attrition, and my Mercedes is winning.

Cliff

vstech · #2 08-07-2008, 01:13 AM

the starter solenoid can cause all the problems you are describing. get it tested.
where is the kill switch on the car? if it's on the neg terminal of the battery and the battery STILL drains, you have a bad battery.
if it's on one of the small wires on the terminal block, I vote for the starter...

renman · #3 08-07-2008, 09:32 AM

The kill switch I purchased and installed is on the positive side of the battery. It was installed according to the instructions. There is a tickler wire on a fusable curcuit that make the switch work. It is a Intellitec Battery Disconnect Relay 100 amp 12 v from http://www.EcoVantageEnergy.com, marketed primarily to the Rv and boating industry. The rocker switch is mounted in the trim panel under the steering wheel. When you toggle the rocker switch back, you can hear the plunger in the switch working. The car is totally dead after you hit the switch. The radio even has to be reprogrammed after the car is turned back on. I opted for this particular device, because you don't have to activate it outside of the cabin of the car. I was obviously hoping this was the final solution to this problem, but that is not the case. Thank you for the reply John.

bbail2x2 · #4 08-07-2008, 12:03 PM

Firstly, I don't know a lot about MB's but I do know trouble shooting methods. it sounds like an intermittant problem, not happening consistantly. (it was draining while your wife drove it but then suddenly started working ok) Can you check the current draw while the car is running, like an ammeter? Using the kill switch should elliminate everything except the batterys internal resistance. it can drain itself if it goes haywire. have you checked with a good electrical mechanic about the Saab alternator and how it matches to the MB system? there may be an over voltage or over current spike that frys the battery or another component. this would happen again even if you changed the battery, possibly.
something to think about anyway. Hope this helps.

renman · #5 08-07-2008, 12:19 PM

Regarding the Saab Alternator, there is ample information on the forum regarding the use of the 110 amp alternator from California Alternator with a 300D Mercedes. Lots of guys have done it. Yes it is most definitely an intermittent problem. Sometime months back I attached my meter to the cigar lighter and checked usage while driving. At the time it was well within the normal range. I don't remember the exact amp readings now but I will check it again today. I have a very good meter. The obvious problem is that it is an intermittent drain and hard to pinpoint. Even last night my wife made the point that she had not turned on any devices such as AC and lights when she was on the way up to her destination. Even so the battery was unable to provide the power to start the car after just a 45 minute drive. Thanks.

blackestate · #6 08-07-2008, 12:39 PM

I have had this symptom with bad voltage regulators. Sounds like a regulator issue. IF you were drawing eneough power to cause the lights to dim, there should be something very hot. A Alternator will drain a battery quickly, if the VR is stuck on when the car is off.
I could place a wrench at the front of the alt and it would pull it in due to the magnetic force in the alt, caused by a bad VR.
If that is it, then you would need to see why the VR is going bad, or being told to stay on?

renman · #7 08-07-2008, 05:18 PM

So you are saying the alternator/voltage regulator I just put on less than a year ago might have been bad or was damaged , or went bad? I guess anything is possible, and I am not discounting this line of thinking, but:

The battery discharge issue was there before the alternator was replaced.

Why haven't the shops I took the car too, ever noted the spike or drain when checking the charging system? Wouldn't this much drain be apparent?

Wouldn't this kind of battery drain be evident if I put a multi tester on the system while driving the car?

Anyway, the car battery is charging now and I will have a chance to look at it hopefully tomorrow evening. Thanks for chiming in. As long as this has been going on I feel like I'm spinning my wheels big time.

blackestate · #8 08-08-2008, 12:43 AM

It has to be something that is intermittent. and the voltage regulator is the only thing I can think of. I am new to these. But the change in headlights give a sign of low/no charge going to full charge. Or a large drain.
I am new to these, so I am going off of past with other cars.
It could be an ok VR, but there is something wrong with the signal to it that is causing a malfunction? I do not know how they work on these cars.
I took out 5 VR on a truck, then finally found the throttle cable laying on a GP relay and shorting out, causing the VR to fail. Replaced the cable, and no more issues....