PeachParts Mercedes-Benz Forum - View Single Post - Slow Battery Drain How To Test and Repair 1980 300D

rhodes2010 · #13 08-29-2012, 01:44 AM

All fuses removed.
Charged battery.
Let checked to see if it starts. Waited 24 hours tested again.

Added minimum fuses to operate vehicle - low beam headlights, left front window, brake lights, turn signals.

Waited 24 hours, tested again - still starts.

Added more fuses. Aux Fan, Clock and Dash Lights, front right window.

Waited 24 hours, battery too dead to start.

Took back out the added fuses , hooked up battery charger.
Started checking current draw on those empty fuse slots.
Only two fuses appear to have current with key off.
1. Aux Fan (b I think - top right)
2. Clock/Dash number 3 - bottom left , 2nd fuse.

The Aux fan drew zero.
The clock , when ammeter across the fuse terminals,
pulsed just like the second hand would pulse.

Small charge was enough to start car.
Check voltage at battery and got 13.5 to 14 so I presume alternator is charging.

I am now thinking of pulling battery and returning for replace under warranty.
Would like to have it tested as I hate random part replacement,
prefer to find the culprit.

This car is our spare and I want to know that the car is dependable.

Any suggestions on this slow battery drain are appreciated.