Doug427

Why in the world is my battery completely, totally dead? Not a volt. The front right strut is apparently leaking, so I parked the car for 2 weeks while I ordered a new strut and went off on the road for work. I came back to the deadest battery I have ever seen. I have left the car in the past for longer than this, and never had the battery die. Is it just coincidence? Was the Airmatic pump running with the car off to try to keep the strut inflated? I doubt it, I'm almost sure that can't run with the key off. Where do I begin, after checking out the battery? I have it disconnected from the car now and charging to a full charge. Once that's done, I have a Solar BA5 that I'll check the battery with once it's fully charged. Assuming the battery checks out OK, where do I begin to try to determine what went wrong? Everything was turned off like normal.

One odd thing, after I started the car with a jump box on the battery in the trunk, a minute or so later the siren started going off. I would get it to go off with the remote, but it would start up again. It would do that if the engine was running or not. Does that indicate anything?

bbirdwell

Youtube has numerous videos on how to perform a current draw test using a multimeter.

Unknown if this is the case on your car but the alarm siren has an internal battery; when that battery's voltage drops too low due to age, the alarm will sound (but intermittently). Only solution is to remove and or replace. If the siren battery still good, it sounds like the voltage levels in the car are incorrect and the distributed digital control system is producing multiple errors between modules; all sorts of crazy things will happen then.

FWIW, the main battery should be rated at 900 CCA. New, mine tested at 982 CCA with a Solar BA-5. I killed the old battery when I left the parking lights on for several days; never could get the batttery to come back. SAM's had a decent deal on an Autocraft Platinum H8AGM battery for my car for a cost of $160 including tax.

sjc246

Sometimes the pump relay can overheat and stick if it is running excessively. It might have stuck on when you parked the car. The alarm siren is probably going off because sitting with the main battery dead caused the alarm to discharge the internal backup battery and now that is dead too. I would start by fixing the leak and replacing the pump relay and main battery and go from there. Keep an eye on things because you dont want to kill the new battery too. OEM batteries are actually reasonably priced (for MB parts) and definitely worth it IMO.

Doug427

Thanks so much, bbirdwell. I think the battery is a goner. I have a fairly primitive old charger, it's only got a high/med/low rate of charge needle meter. It started pegged on high, and while it's now down to medium it came down very slowly. I guess it's time to retire the 1972-era charger and get a new one. If anyone has an idea what is a good one let me know. The question is what killed th battery? It was prefect when I parked the car the other day.

As for the alarm battery, is that rechargeable? Will it recharge itself as I charge the main battery? Or do I need to replace it? I didn't even know I had one - where is it, does anyone have a part number or something for it? I don't know where to start with that.

I've got the battery disconnected from the car while I charge it, tomorrow morning I'll use the Solar BA-5 on it and see where it stands. This all started with a bad front strut, and I haven't even touched that yet!

Doug427

All good ideas - where is the relay located? Do you know? I checked for leaks as best I could and found nothing. I figured it must be the strut, so I have a re-manufactured Arnott here now. I'll put that in and hope the leak was internal to the strut and go from there.

bbirdwell

Doug427

Update - the Arnott strut is in, car seems level again and doesn't seem to be sagging. The battery was left on the charger overnight and seems to be holding a charge. I have to disconnect it again to check it with the Solar BA5. I don't believe I can check it with the battery connected to the car. I did check the Airmatic pump relay, it looks fine, no melting, burning, etc. I sat next to the car in a closed garage with the car turned off and nothing at all is running, so I think I'm clear on that issue.

Here's the problem....now every once in a while the damned siren goes off. Can I just disconnect the darned thing and/or code it out with STAR? I believe it's located inside the wheelwell line on the drivers side. What's better - code it out, disconnect or both?

I have to check the main battery with the Solar checker. I was just eager to get it hooked up and running to see if the suspension issue has been solved - one problem at a time. I seem to have that solved, now on to the battery/siren issue. I presume from reading that the siren has a small battery inside it, and when the main battery dies, that one starts serving to power the siren. When that goes dead, it's done. Can't be recharged or replaced. Is that right?

Thanks,
Doug

Rallyboy383

Correct! You have to replace the siren. I just did it on mine.

KAMG

The siren is in the behind the fender liner on the driver's side, approximately behind the V8 Kompressor badge. I'm not sure what powers the siren unit or if there is a small battery inside it, but most people just replace the whole unit, it's less than $200. Part number is 2198203226. AMGMeister has an in depth video on Youtube for its location and replacment. The lock/unlock chirps can be disabled with STAR

Doug427

I checked the battery with the Solar BA-5. It shows as good. I guess I'll keep it and see what happens. I just took the car on a one hour or so drive. It runs perfectly, and no more siren. I don't know why.

One odd thing I noticed is that the power trunk open/close function doesn;t work anymore. I guess after having the battery disconnected for a whole 2 days it needs to be reset or relearned somehow. I'll have to research how to do that, unless anyone knows off the top of their heads and can post a quick note here. I imagine there are other functions that will be wacky that I haven't noticed yet due to the battery disconnect. I figure it out as I go.

So far so good. Hoping the battery doesn't go dead again.

cetialpha5

For the trunk closer, try normalizing it. Open and close all the windows holding the buttons down/up for a few extra seconds when they are fully up/down and also doing the same with the sunroof. Also try the button on the driver's door, use that to open and close the trunk.

As for the battery if it turns out bad, Pepboys has the Champion AGM on sale with a $40 rebate so about $118 after the rebate.

Lots of things can cause the battery to go dead, seat control module is one that comes to mind.

Doug427

I'll normalize everything when I get home, then hook it up to STAR and see where it's all at from there. The car drives remarkably better with the new strut in it. I'm hoping the dead battery was just some quirk, although I know it has to be from something. Now to find out just what that something is........... More work to be done once I get home on Monday.

sjc246

You disassembled the relay and inspected the internal contacts? While it is possible, even inspecting the internal contacts isn't always 100% and you wont typically see any signs of damage on the outside. It is possible for the relay to show external damage (melted case or burned pins), but it is not typical and the lack of external damage does not prove that the relay is ok.
That said, there is a very good chance that the relay is fine, but replacing it is very cheap and easy so it's usually better to be safe than risk ruining your battery and/or getting stranded somewhere. Many if not most MB dealers replace the relay when replacing any leaking airmatic components due to the possibility of relay damage: the pump and relay are only designed for intermittent use so excessive use, in the case of a leak, often causes damage (the relay can be continuously actuated without problem, however, it cannot sustain the high current consumption of the compressor for an extended period without damage to the contacts due to heat).

tw2

Just a side note for next time, the solar battery tester works fine while the battery is connected.