Battery Goes Dead Once In Awhile
 

A friend of mine who owns a service and repair facility near by has a client with a peculiar problem. The car is a 91 190E 2.3. With no rhyme or reason the battery goes dead every 3 to 4 to 5 weeks. The shop has tested key off drains and everything else. They even changed the alternator as a possible intermittent problem. After the battery is recharged, there is no problem until the next dead battery which may be several weeks down the road. Any one seen this or have any profound thoughts. There are 3 drivers who share the car and know how to connect the battery booster that's kept in the trunk,so please no posts about someone leaving the lights on or dirty battery terminals or something like that. This has been going on for about a year. I'm hoping someone else has experienced this anomoly.

Thanks,
Peter

One more clue. Last week one of the drivers started the car in the morning and drove the car to Sunday services where it set for about an hour. When she came out the battery was dead.

Thanks,
Peter

Thanks for the input. Good point about battery smell or temp or something. The owners could observe and report. I too am not sure when the discharge is occuring. No, the charge light does not necessarily come on with a malfunction.

Thanks again,
Peter

If this one has the seperate amp/tuner audio system, it sounds like the amp or tuner is not switching off consistently. This one can be a bear to solve but, I've found simply unpluggin the amp and turning the client loose with the car to be the most effective metheod of testing. I show them where the connectors are and intruct them on how to replug them in as well.

If thats the problem its either time to go aftermarket (which sounds better in these earlier cars) or remove the head unit, amp or tuner (which ever one is staying on) and send them the Becker USA for repair.


Joe

You mention that battery was dead after a warm engine had been left to cool for about an hour whilst in church. (Assuming that you are saying the battery is dead by symptoms rather than tested at this moment in time) then this reminds me of a problem we had with a car where it would perform normally but battery would appear to die occasionally. This narrowed down to it appeared to die if you tried to restart when the engine was around the same temperature ie. not cold, but not up to running temperature. The actual fault (apparently quite common on this non Mercedes car) was caused by the battery positive lead fragmenting inside the insulation caused in this case by the lead running close to the exhaust where the consent hot and cold had caused metal fatigue in the lead. When cold the insulation held the core tight enough for a good connection, when hot the core had expanded enough for a good connection, at a temperature in-between then the fragmented core become high resistance when trying to draw a high current. Just about impossible to find as a fault by testing. Might be worth changing some of the big leads that may look and test perfectly OK when tested, but might be routed such that they may suffer from fatigue caused by heat or physical vibration...

Thanks for all the input especially. There is a good chance that it is something weird like that. I may as well end this thread, because the lady traded the car in. I'll bet she forgot to mention the little problem. My friend was happy that the car just went away. I asked him if it wouldn't be funny if a new customer shows up in a couple of months and says," I just bought this car and it has the strangest problem."


Peter

Maybe I missed it somewhere in the previous posts, but
 

have you really verified that it's the battery and not another gradually failing Bosch starter? I've not worked on a 190, but on the older German cars (especially air-cooleds) these often develop a "stickiness" inside the solenoid so that sometimes it engages (usually when cold) and sometimes it won't (usually when hot). I've fixed a lot of them for myself and for friends by disassembling everything, polishing the big contacts inside the solenoid, and then relubing it all carefully with high-temperature stuff, but if you've got to pay a real professional, it's probably better nowadays to just have a rebuilt put in.

Often a starter with these sorts of problems will kick in if someone gives it a whack with a wooden or rubber mallet while someone else holds the key in start position, but they often also deceive you buy working when jumper cables are attached, for some reason (perhaps the higher voltage from a running alternator, but I've seen it happen with an extra battery, too).

An afterthought on the way home last night:
 

It was damp and the windows were all covered with condensation when I got in the old 300TD, and then I remembered: check out the rear window defroster circuits to verify that it's not staying on and drawing down the battery after short trips. These things take a lot of amps, and on most cars there is a timer in the relay which is supposed to prevent the system from staying on longer than a brief number of minutes if someone forgets to turn it off, but on several non-Mercedes European cars which use the same relays, I've seen the timer fail and cause dead batteries in this fashion. Of course, it could be that someone is just misusing the system, too.

Fit,

These cars don't have mechanical voltage regulators anymore. They are solid state and built into the brush block assy. The alternator has been replaced with the exact same problem occuring. I doubt that the rear defroster is the problem because this has been going on for a year noe, and you have to remember our moderate climate in CA. The defroster would only be used a few months per year, and we don't have the 100% humidity you have. I lived in Virginia for a few years. Besides as I said in my last post, the lady sold the car so we may never khow. Thanks for the input though.

Peter

I didn't say a word about voltage regulators!
 

I was talking about the solenoid on the starter. I surely have a lot of experience with late model Bosch integral regulators on various SAABs and BMWs, besides my old 300TD, but I didn't mention that item at all in previous posts.

Fit,

After rereading the post I see you did say starter several times. I appologize. I pride myself on careful listening and attention to detail, but I think this time I had my head up my ass.

Peter