DUTCH

Are any of the 12 volt power sockets continuously on independent of the ignition? In my Q7 they were always on. It doesn't look to be the case with this ML.

We're planning a cross country trip with a 12 volt Engel fridge; and there will be times where the car is parked and turned off. I would like to be able to continue to supply power to the Engel when parked.

Is there any way to activate this using the STAR diagnosis computer?

Please advise. TIA!

350MH83

Im not sure this can be done, but I would rather pull a wire from the 12V battery input below the rear passenger seat straight to the 12v outlet in the cargo, and just add a switch and a fuse on that additional line. You just need to make sure this is a double switch that will open the live wire from the original wire when it closes the newly added one, so that the fuses values dont add up.
Overall that shouldnt be too difficult to implement.

350MH83

That's the type of rocker switch Im talking about.

DUTCH

Good idea, too; but I've already considered and rejected that idea. The positive terminal on the battery is located to the front under the seat; and requires removal of the battery to access it. If I remove the battery, there's a whole lot of reprogramming of the various functions in the car that must be done; and I don't want to have to mess with that.

The other option is to tap the two poles located under the hood which are used to recharge or jump start the battery. They're very accessible and would only need to be used when the car is parked.

It's really a shame that MB makes this so hard! The much better way would be to do as is done on the Audi Q7. The 12 volt sockets are always hot, but have a sensor that disconnects them if the battery approaches too low to start the car. Good engineering sense seems to be beyond MB's ability sometimes.

Nanook

Actually you can disconnect main battery without losing any programming..there is a supplemental battery that maintains all settings..

DUTCH

Not so according to the WIS. Standard procedure is to reprogram after the battery has been disconnected. Maybe the WIS is wrong.

DUTCH

Best solution is to power off the trailer hitch electrical plug. There is always on +12 volts and a ground in there.

I took a 7-pin plug and wired a female cigarette socket to it. When parked, I'll disconnect the trailer, plug in the 7-pin cigarette socket adapter, plug in the Engel and all is good.

Nanook

I disconnected my battery when I sent the ECM in to Renntech and no reprogramming was needed when I reconnected..In my vehicle I'm certain there is a backup