Have my 2020 AS Shorty since 9/19. Been in for service over 6 months time. Many minor issues but what kept bringing me in was rapid discharge of the house batteries. After much research, discussions with the dealer and Tech Support at Jackson Center I endeavored to fix it myself.
After installing a Victron Smart Shunt I was able to finally see where this power was going! To the chassis battery! When the house batteries are connected and the Mercedes is awake, but NOT running, I was getting discharges of 15-20 amps. Turn the house master off, 0.1 amps discharge. To further confirm I disconnected my chassis battery, turned on the house, opened the driver door and the chassis powered up pulling power from the house. So now I knew why my batteries drained in 5 hours too!
DISCLAIMER: Iím not a mechanic, electrical engineer or any other expert. (Not with Airstreams at least). So my advice is advisory only and use it at your own risk. In no way am I liable for anyone using this advice.)
So what was causing this? Under the driver seat is the Victron buck boost DC/DC converter. There are two lights on it. A simple way to see if anyoneís issue are the same as mine is to look at the status of those lights. With engine running you should get a green and purple light. Engine off only green. Try turning on the master disconnect with the engine NOT running and see if you get a green and purple light. If you do youíve got my problem. Without getting into detail about why, your house batteries are turning on the converter allowing power to pass to the chassis. Open the door and the chassis starts sucking amps from your precious house capacity. Camp off grid and at night youíll be without juice in hours.
So how to fix it? I came up with a workaround because to fix it correctly requires a lot of work which Iím not doing. (Iíll make the dealer do it but for now I can go camp) After swapping wires, changing configs in the Victron Buck Boost Converter I finally discovered the problem and a relatively easy fix.
If , from from the above observations, this is your problem youíll need to remove the seat. Just the 4 torx bolts. Shift the seat forward and youíll be able to see the input and output cover for the buck boost. Remove the 2 tiny screws and youíll see a purple wire. This provides a signal to turn on the buck boost. Again you can verify this is your problem by pulling this connector off, turn on your house batteries and see if you only have one green light. If you do my fix should work. Put inline a simple 12v
low amp on/off switch on that purple wire.
When you have your house on with the engine NOT running turn it OFF. Buck boost stays off. No more chassis drain.
All other times , engine running, shore or generator power i switch it on allowing all normal charging functions to occur. This includes charging the chassis batteries.
Good luck. PM me with any questions.