[iridium_moon]

My U3000 chassis currently stands unused while I build a camper. The (new) 125Ah batteries keep going flat every few weeks. Today I investigated and measured a constant current draw of 300mA at 24v, a drain of 7.2 Watts.

This level of load will theoretically drain 125Ah to dead flat in 17 days, which sounds about right. It will ruin the batteries if it keeps happening.

Has anyone else had this problem? The tacho clicks and whirrs constantly: does a tacho use a constant 7.2W? I haven't pulled fuses and checked other circuits yet as it does sound possible.

The vehicle is plated at 7.5t, and will be registered as Private HGV / Motor Caravan, so I don't need a tacho anyway. Does anyone know how to disable it? Pulling fuses alone would throw up a load of distracting error messages, as it does now when there's no disc present.

I guess it's a software setting. Does this need a main dealer? Is it a big deal, or just one box to click?

Any help appreciated!

Mark

 

[m37charlie]

You probably can turn it off with a Star Diagnosis System. Can you meet me at Unicat in Dettenheim in Germany Tuesday morning May 23? Or else a dealer could do it, or else you could buy a diagnosis system
yourself.
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Charlie

 

[iridium_moon]

You probably can turn it off with a Star Diagnosis System. Can you meet me at Unicat in Dettenheim in Germany Tuesday morning May 23? Or else a dealer could do it, or else you could buy a diagnosis system
yourself. ...

Hey Charlie, thanks for the offer of help - I'd be delighted to visit Unicat one day, but for now I'll just buy the diagnostic system. I spoke to ProAuto Diagnostics in Derbyshire, UK. The owner is a very helpful chap who offers lifetime assistance with the software.

He assures me his lower-spec C3 version, sold loaded onto a used Dell laptop for GBP 500, will do the job, and that I don't need the current C4 version, which costs twice as much.

https://www.obdstore.co.uk/product/mb-star-c3-mercedes-diagnostics-mulitplexer/

 

[TRUKTOR]

Hi - my truck has no computer, so I
Can't selectively decide what functions that I want to put to bed, outside of pulling fuses.
So, I just make sure I turn the battery switch off. This kills the tacho, and the only function that this affects is the Clock (in the Tacho), as it has to be re-set to the correct time. I usually don't even bother with that, unless I'm on a trip.
I recently ignored my UNIMOG for a good period of time - 2 years
Is a good guess. I approached the dusty mess, expecting the worst. I turned the battery switch on, climbed into the cab and turned the
Key. To my utter amazement, the truck fired up immediately - I mean, it could not have started any faster, and then it settled down into a nice idle. That was a good surprise, as I was planning on charging the two dead batteries and all of that, with my key locked into the ignition...
So, that is a simple solution to the Tacho issue that works for me,
but perhaps your truck has more sophisticated reasons to keep the batteries on while it is sitting.