Battery Drain - Help! - PeachParts Mercedes-Benz Forum

JeffreyNMemphis · #1 06-04-2018, 02:08 PM

Hello Peaches,

Something is draining the battery on my 1962 Fintail 220Sb. My multimeter shows 0.55 amp draw from the battery. I removed one fuse at a time from the box and the draw was constant without fuses.

Next I will disconnect the alternator and then the starter.

Any suggestions?

Thank you!

Jeffrey

Mike D · #2 06-04-2018, 02:16 PM

Clock?

Tomguy · #3 06-04-2018, 07:52 PM

Disconnect the alternator (it's the easiest). Sounds like there's a short, either in the voltage regulator or the alternator. I believe you would have an external regulator on yours.

Mike: The clock only draws when it's winding, which takes about a second, and only does it once every few minutes.

Mike D · #4 06-04-2018, 07:57 PM

Just a guess. Thanks for the clarification.

Benz Dr. · #5 06-04-2018, 11:41 PM

Clocks usually run from fuse number 1 which is always live unless you remove the fuse.

JeffreyNMemphis · #6 06-05-2018, 09:17 AM

I disconnected the alternator and the drain dropped from 0.55 to 0.08. The single wire 96 amp alternator replaced the generator and voltage regulator. The alternator is compatible with a 1992 Chevy Camaro.

The alternator charges so I don’t know if I should take it back to O’Reilly auto parts and buy another one. It worked very well and wasn’t draining my battery before the engine swap. Is it normal for the alternator to draw current from the battery?

Breaking News! I found a donor 1962 220Sb with 76,000 miles with an unrestorable body and interior. I removed the oil pan and cleaned it before resealing. I am confident that I have a reliable engine to last my lifetime. The original engine blew a rod through the engine block at 219,000 miles.

JeffreyNMemphis · #7 06-09-2018, 01:28 PM

Hello Peaches,

Problem solved!

How to check a suspected battery drain? Disconnect positive terminal of the battery. Position multimeter switch to 10a and move ground to the 10a position. Touch leads to the disconnected battery terminal and disconnected battery wire. 0.55 was draining my battery. I checked all my fuses first by removing one at a time with no change from 0.55. Removing the alternator and checking gave me 0.08 which is not going to drain the battery.

I replaced the alternator today (O'Reilly lifetime warranty is a good thing) and checked with above procedure and had 0.08 measurement. So it appears that the alternator was draining my battery.

Best regards,

Jeffrey

Paulwho · #8 06-09-2018, 01:51 PM

Quote:

Originally Posted by JeffreyNMemphis

Hello Peaches,

Problem solved!

How to check a suspected battery drain? Disconnect positive terminal of the battery.

Jeffrey

Sorry to be safety aware but on a neg ground car the neg must be removed first. When removing the pos first, an accidental short circuit can occur with the wrench and the fender. This can blow up the battery. A friend lost his eyesight when his battery exploded.

JeffreyNMemphis · #9 06-09-2018, 02:15 PM

Hi Paul,

Thank you for letting me know that. I have no official training or school for mechanics. I am teachable and fearless. If I lost an eye it would be very bad.

Thank you for sharing!

Jeffrey

Idle · #10 06-10-2018, 06:12 PM

Quote:

Originally Posted by Tomguy

Disconnect the alternator (it's the easiest). Sounds like there's a short, either in the voltage regulator or the alternator. I believe you would have an external regulator on yours.

Mike: The clock only draws when it's winding, which takes about a second, and only does it once every few minutes.

A word on clock operation....

These older clocks work off a thing that looks like a set of ignition points. When they close up they 'fire' and this pushes the arm back. The pushing of the arm winds the clock.

Then it ticks down and the arm gets close to the other side of the 'points', touches, fires, and the whole thing starts over again.

I check these older clocks with a 12v power source. It still seems weird to see the clock keep operating for a few minutes after I remove the power.

Rook · #11 06-10-2018, 06:39 PM

If you hadn’t figured out the problem I was gonna ask about the radio. My folks ‘61 220S was the only car I recall where the radio was not wired through the ignition key and we had to make sure it was actually off and not just low volume.

I remember when working car clocks were an urban legend cuz no one had ever seen one.

JeffreyNMemphis · #12 06-11-2018, 11:03 AM

Quote:

Originally Posted by Idle

A word on clock operation....

These older clocks work off a thing that looks like a set of ignition points. When they close up they 'fire' and this pushes the arm back. The pushing of the arm winds the clock.

Then it ticks down and the arm gets close to the other side of the 'points', touches, fires, and the whole thing starts over again.

I check these older clocks with a 12v power source. It still seems weird to see the clock keep operating for a few minutes after I remove the power.

The VDO clocks made for Mercedes Benz between 1955 and 1972 were electro-mechanical. They still worked on spring power like a pocket watch but have short springs that were rewound every minute or so. The later models after 1965 could beat for five minutes on a rewind.