Brian McL

I have a quick question which I think is pretty simple but I just need clarification.

I have a R129 500SL with a battery drain.

I’ve checked it with the multi meter and it shows a steady 48mA BUT every minute it jumps to 120 + - for a split second which is when the clock pulses.

Is the jump normal when the clock pulses? I expect it is and therefore not enough to drain the battery.

Am I correct in assuming that ?

Thanks for the help.

CaliBenzDriver

Yes you're right the clock ticking is hardly draining your battery.

What does drains abnormally is when a module or more fail to enter low power state.

I suggest you start by scanning your car for fault codes.

It is 50 to 60% possible that an unknown module was swamped with rain intrusion and developed green oxide.

What year is it?... mileage?

At some point I suggest disconnecting battery power for 15mn but this may drive your windows, sunroof, radio and steering wheel a bit crazy for reset.

I leave that up to your threshold for adventures. Nobody knows everything about your car.
✌️

Brian McL

Thanks for the reply. It's a 1990 500SL with 80000 kil.....Japan grey market.
Dumped and cleared the codes, and there are several, but no way to know if the are historical or current.
We'll see if any return.
Constant 45mA with the exception of the spike to 120mA from the clock every minute.
Car seems to be OK with no drain after 8 hours and 24 hours.
One small bit of information my wife offered as I was scratching my head wondering "why why why"....
"I did leave the key in the ignition..do you think that mattered?" she asked.
"YES....if it was ON !!....was it on?"
"I don't know....sorry", she said as she placed a coffee and gourmet sandwich on my workbench for lunch.
"Thanks dear" .....ugh
So, that may be the problem...
...and thanks for the reply.

CaliBenzDriver

Given the right gourmet food.... no problem.

Do you use a "CTEK float charger" ?

Get yourself one to maintain your battery in perfect condition.