Battery drain
 

I have an 1987 mercedes 420 sel ---i put a meter on the neg. cable and battery terminal and its shows 0.10 draw on the battery i guess that would be milimeters, is that enough draw to lower my battery that it won't start after a week or so of not being used ??
Thanks
jlw15

It depends on what scale you had your meter set to.

If you had it set to 10A, then that means 100mA.

Yes meter is set at 10A

when alternator go bad sometimes they will draw power..I had to replace mine

A 100mA draw shouldn't kill a healthy battery in just a week. The normal rest current draw for that car is at least 50-60mA so you're only looking for a 40-50mA problem. Star by removing the fuses one at a time while watching the meter.

Try removing the clock fuse to isolate the leakage . Leaky capacitors in these clocks are common .
good luck

Adler

so what your saying is if my meter is set on 10A and reading 0.10 that shouldn'r be a problem???? i pulled all fuses from fuse box from under the hood except the square silver ones and nothing changed on my meter---not sure where to go from here

I just have a cheap meter that will read 10A ---other day i opened the door to check meter was working and it did show about 1.30 when door was opend---had a load test done on battery and it showed to be good

1.3A draw with doors open sounds correct. I'll check my 420SEL in a bit here and see what the battery drain on it is..

Edit: Here you go. Looks like 20mA is the nominal draw on the battery. You've got something extra pulling power.


http://i.imgur.com/RcErml.jpg

Ok---Where do i start looking ?? i pulled all the fuses under hood in fuse box except the square metal ones and nothing changes and even when i pull the clock fuse it don't even change---Help Please

Do you have any wires coming off the positive terminal aside from the factory mercedes ones that are on the connector?

No--Main positive wire and one thinner wire---car is stock---today i pulled the clock fuse and meter read .08 with the fuse in it bounces from .09 to .10 like everytime the second hand moves it goes to .10

80mA isn't that bad. That can be a combination of things like the radio,alarm,immob,telephone,clock,etc all drawing a little current adding up to 80mA. Don't worry about it unless you experience trouble. If the battery drains in less than a week something is wrong or the battery is defective. To give you an idea : a standard LED draws about 10mA and can run about 6500hrs(270 days) when connected to the average car battrery(657).

I know when the battery was replaced a couple of years ago i wasn't there and the mechanic did not put the proper battery replacement in---i have had this battery load tested and it shows fine---i only drive this car once every couple of weeks and in that amount of time the battery won't start the car. ----if i disconnect the battery it stays charged with no problem.

You might want to consider trying this. Just below the battery on the firewall closest to front of the car there is a distribution block. If you put your meter in between the positive terminal and each individual wire/wireset (removing them one-by-one) you might find that your drain is coming from the alternator or fuse box or starter. I know when my 190E's alternator went it produced a large draw on the battery.

when i'm checking each wire in block with meter do i leave the battery connected and put my meter on 10A and if i show a draw on a wire thats the problem??
thanks

You should disconnect the main positive battery cable from the battery. Then disconnect the wires from the block and put your meter between the positive post and the wire. It should be fairly visible where each wire goes. One or two should go to the starter, alternator and main car fusebox.

If you show a power drain on the alternator or starter wire set that might be indicative of a problem. If you find no drain on the starter or alternator wire sets thats a good sign that and your drain is elsewhere.

After pulling wires from block all were good except the one going directly to the fuse box that one was showing 0.09 on meter. Now What "LOL" i hope thats good news.---
I really do thank everyone for their help because i need it.

Well the next step is keeping the meter hooked to that wire alone and pulling each fuse one at a time until you see the number drop to zero. If you do that and see no change at all, perhaps unplug the anti-theft alarm unit I think its in the passenger footwell somewhere.

Do you have the under hood light disconnected?

I don't believe any of these cars ever had under the hood lights... trunk yes but I dont recall engine compartment.

Just checking. It wouldn't be the first time I've had something simple which I've overlooked drive me crazy.:o

The battery drained every three days on a 71 300 series dodge van. I used it just on weekends or during times when my wife or I needed to transport all six kids of our children.

I traced it back to the cluster/steering area by following the drain from the battery one wire at a time. It turned out to be the emergency flasher mounted on the steering column. It was the old push button under the column type which has burnt out thereby not flashing when pushed.

Somehow, someone had pushed it into flash position. I pulled it back into off position and the problem was solved.

No hood light---your thinking the anti-theft alarm is inside the car passengder side kick panel on the side ??? pulled panel inside to the front seems to be the air bag and in the right kick panel could be it.---- but not sure how it disconnects---there is a rubber boot coming into the top of it--i don't want to break anything if that is the anti-theft your speaking of

Yes the anti-theft unit is located under the passenger kick panel. It has BECKER written on it:

http://i.imgur.com/D9tZql.jpg
http://i.imgur.com/erIL8l.jpg

OK mine looks just like that---where do i unplug it at??? several plugs

you probably don't need to unplug it, you can probably find its fuse:
http://i.imgur.com/fR5pFl.jpg

It looks like Fuse 15, 6 and 8 supply it signals in one way or another. The main power seems to come from fuses in K position of the fuse & relay box:
http://i.imgur.com/wy44Dl.jpg

Hate to be such a bother--- after looking again at fuses my car does not have a K i only have the 6 square ones behind it on your picture and the A, B and G and i have a double 3 even so its not numbered on mine

no bother at all. yes, those should be regular fuses in position k.

Pulled fuses from 15--6--8--and K postion and still meter is showing 0.09 on 10A setting--------Question----the rod that locks the gas cap door i don't have in place anymore that shouldn't cause a problem with it not being in place should it ??

No I dont think the fuel door lock would cause any problems other than not having the fuel door lock when you lock the car. The locking system is vacuum powered.

any thoughts on what i should check next

Have you gone through the fuse box again, pulling all the fuses? There may be additional fuses around the fuse box, I can't remember if there are or are not but look around it.

I'm running out of ideas at this point, hopefully someone else will chime in as well.

Yes have pulled all fuses again---should i pull the relays ?? if so do they pull staright out ?? where would i unplug the anti-theft at just to make sure it is completely disconnected from system for possible problem there ??? how long does it take for the alarm to go off if hood or door is opened with alarm set ?? to make sure it is working correctly ??

Hmm. You can pull the relays, they pull straight up/out. After you've removed all the fuses you can just unplug all the connectors on the anit-theft unit. Its a fairly instantaneous alarm. It will honk and horn and flash lights I think.

If you lock the car with the passenger side door open, then unlock the car by pulling up on the passenger side locking plunger thing, the alarm should sound.

Locked passenger door with square key with dot with door open--pulled up on locking thing all doors unlocked and nothing happened---then rolled down window with door closed and locked doors and then pulled up on locking thing and opened door and alarm still did not go off---i can remember years ago when car was still in Calif in my aunts garage and i didn't know about the different keys for setting the alarm and i would use what ever key was handy---car would stay locked in the garage and she would tell me that the horn would start honking in the middle of the nite at times and then i read the manual and realized what was going on. So since it wouldn't go off for me now that might be my problem----is the anti-theft alarm the whole thing in the picture you sent me inside the car or just the part on the left side that needs to be unplugged ??

I'm not sure if what you did would actually trip the system. I don't have much experience with it actually.

I just drove a 560SEL back from NYC this past weekend and accidentally triggered the alarm on it. The unit in the picture i posed with BECKER written on it is the alarm module.

Thanks--on Monday i wll check with a Mercedez mechanic and see what he has to say about how the alarm works

I'm Happy----Disconnected the anti-theft alarm and it dropped my meter to 0.01 and yes the alarm should go off almost instantly once you have it set and try to open a door per a mechanic---thats something at this point and time I'm not concerned that needs to work but at least i know i can let the car set a couple of weeks and the battery should still be strong enough to start the car. Thanks to everyone with their input on my battery draw problem
Jeff