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1980 450SL
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96 Posts
Discussion Starter #1
Hi Fellas..My car came with a trickle charger attched to battery...Just curious to know how difficult or expensive to track down power drain problem. I can go a couple days without charge before battery is too far gone, replaced battery a couple years ago, thought might solve the problem.
 

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One of the BW Old Guard/R129, W204 Moderator
1997 SL500- 40th Anniversary
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7,166 Posts
Hi Fellas..My car came with a trickle charger attched to battery...Just curious to know how difficult or expensive to track down power drain problem. I can go a couple days without charge before battery is too far gone, replaced battery a couple years ago, thought might solve the problem.
Let us know if the climate control (A/C) servo is kaput... common battery killer on cars of your vintage...
 

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R107 450sl
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10 Posts
Are you sure that it is battery drain? Have you checked if it is charging properly.
Tracking down the battery drain should start at the battery. You should measure (any instrument capable of measuring electrical current will do). Engine stopped, keys out, doors closed. Take the terminal off the battery, connect the instrument and read how much current is passing through. at the steady state I'd expect no more that 50m Amp. That would be a clock.
Anything more than 150 mAmp would mean that you have a drain. Check the boot light, although it should be 5W bulb. 5 W bulb would take 100 hours to drain 50AMPH battery.....


Sent from my Autoguide iPad app
 

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1993 600SL, 1973 450 SL,1982 380SL,1998 SLK 230, 1968 Firebird, 2001 Dodge Ram 4x4,2005 Ford Escape
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5,247 Posts
Not sure if the alternator is isolated in a off condition on these cars. If not, weak or bad diodes can discharge a battery.
 

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US spec MB560SL 1986, Audi A4 and A6, Ford Taunus 1964 17M and 2.0 1975
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1,419 Posts
Main Switch

My previous battery died because of it was deep emptied time after time. I replaced it by Yellow Top Optima - this seems to be much more robust during the winter garage periods.

I have also added an electrical Main Switch to prevent the total empty battery. Elelctrical Main Switch is easy and fast to operate - the MS control rocker switch in the hard top connector bay.
 

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Registered
1980 450SL
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96 Posts
Discussion Starter #6
Battery Drain...

Let us know if the climate control (A/C) servo is kaput... common battery killer on cars of your vintage...
Yes the AC and heater are on the fritz...I just don't know what is causing the drain, need to look into it, tired of always having to keep car plugged in.

Thx, BB
 

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US spec MB560SL 1986, Audi A4 and A6, Ford Taunus 1964 17M and 2.0 1975
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1,419 Posts
Measure the drain currents fuse by fuse - it will quide you into the right direction.
 
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