Battery parasite drain
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Newbie
Joined: Aug 2013
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From: Ky
1999 ML320
Battery parasite drain
My 99 ML 320 has a 3.46a drain when I connect my volt meter between the negative cable and and battery post. I pulled each fuse and there was no change. I connected the battery back up and then measured for a voltage drop across the fuses and again there were none. My battery is fully charged and I only have the one fuse box (that I know of). Does anybody out there know where I should check next? Since this past Tuesday night my battery has been draining over night and being dead in the morning. Thanks.
Edit to add: The battery was tested and it tested good. The alternator was also tested and it tested good.
Edit to add: The battery was tested and it tested good. The alternator was also tested and it tested good.
Last edited by luvmyskyrl; Jun 12, 2015 at 06:02 PM.
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Joined: Oct 2011
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From: Bronx, N.Y.
2002 ML 320 & 2006 ML500
Key out of ignition, open hood and all doors closed. Weight down the Anti-theft Engine Hood Switch and lock the vehicle with the remote.
Wait 20 mins. so that all modules go into sleep mode and then proceed with testing voltage drop across all fuses.
Wait 20 mins. so that all modules go into sleep mode and then proceed with testing voltage drop across all fuses.
Thread Starter
Newbie
Joined: Aug 2013
Posts: 12
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From: Ky
1999 ML320
Thanks. I found a 2.6mv drop on fuse 44 (30 amp) Air Conditioning Fan. I don't have any diagrams or schematics so I don't know what to do next. If you have anymore help up your sleeve, I would greatly appreciate it.
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Newbie
Joined: Aug 2013
Posts: 12
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From: Ky
1999 ML320
This morning the battery measured 10.25 v which wasn't enough to start the truck so I put the charger on it for a few hours before I did the tests. On that note, disconnecting X1 didn't change the voltage drop. I then swapped out K26 with K14 and remeasured the voltage drop across fuse 44. The reading I got was 0.0v. Swapping the relays back and remeasuring I still got 0.0v. It looks as if K26 was sticking. I'm going to wait before I do anything else until tomorrow morning. If the battery measures in the 12 v range and the truck starts, then I'll know for sure K26 was the problem. I'll let you know what happens tomorrow. Thanks for all your help.
Last edited by luvmyskyrl; Jun 15, 2015 at 01:05 PM. Reason: spelling
Junior Member
Joined: Oct 2013
Posts: 69
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From: Sedbergh, England
ML320 W163 2000
Worn wires to auxiliary fan
I had/have a drain on my battery (more than one I suspect, another source might be the parking sensors...) but one candidate was that the wires going to the air conditioning/auxiliary fan were worn through to the copper where they had rubbed against a metal edge inside the front of the grill under the hood. This was on the right of the fans (as you look at the front of the car) where the cables go into a plug/socket. It just had the usual useless cloth tape wrapped around the wires so I reinforced that with some insulation tape and a short length of plastic hosepipe to protect it. The fans still work, even if my aircon doesn't - only warm enough three days a year for it, so not a priority!
As a temporary/semi-permanent solution to the battery drain I used a 20Watt solar panel on the dash, plugged into the 12V power outlet (that is live when the car is switched off) - this keeps the battery alive, but is a bit awkward setting it up and removing each time I use the car!
As a temporary/semi-permanent solution to the battery drain I used a 20Watt solar panel on the dash, plugged into the 12V power outlet (that is live when the car is switched off) - this keeps the battery alive, but is a bit awkward setting it up and removing each time I use the car!
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Thread Starter
Newbie
Joined: Aug 2013
Posts: 12
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From: Ky
1999 ML320
Update
I took my ML320 in this morning and they found the alternator was bleeding my battery so they replaced the alternator and serpentine belt. With labor the bill came to $688. I'm a happy camper now. (not that I spent 688 but because I have my truck back).
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