HELP Sprinter Battery

OK, back to the drawing board. I took the charger off for two days and had a dead battery again. Jumped with pickup, turned it around, and put the charger back on.
Note a couple of things.
1. The engine symbol is on and the Sprinter dealer said it was because of two glow plugs not working. No problem as it still cranked and ran OK at the time.
2. Now I see the Brake light is on but not having any problem with brakes.
I'm not sure where to start trouble shooting except to loosen the Negative cable and check for sparks and removing one FUSE at a time.
Your thoughts please and note the dealer is too far away. My local Mechanic doesn't have the Mercedes codes in his OBDII tester.
Marvin

Thanks to all----I have no idea what caused the decline in voltage. It has sat longer at times and still cranked fine.
I will leave the trickle charger on it until the storm passes.
Not sure I understand the purpose of the battery disconnect switch. It is a momentary switch and each time I click it the green light stays on. This could be because I have it plugged into House, 30 amp circuit.
Marvin
PS, The reason I needed it cranked was to place heavy boards on the carport bottom rails and park the RV on one side and My heavy pickup on the other side.
This is so when Irma visits she wont take my CP home with her.

Thanks and pardon my stupidity.
Marvin

Sir, honesty is never stupid. Bluffing or criticizing others personally counts as being stupid.

Tip: Disconnect your battery for now, and deal with it after the storm blows through. Staying safe is job 1.

question what drained the battery.

Kayteg1 wrote:
Do you have manual for it?
With so many different systems, it will be hard to crystal-ball your issue.
Was the motorhome build in US, or Germany?
Don't jump electronic vehicles unless you know precisely what you are doing.
Frying ECM can be pretty expensive lesson.

Yes, I'm familiar with the process.
Battery charged up fine after I got 12 volts to it. Cranks, runs fine now. I took it for a 10 mile test run to charge the battery more.
Thanks everyone, Marvin

Do you have manual for it?
With so many different systems, it will be hard to crystal-ball your issue.
Was the motorhome build in US, or Germany?
Don't jump electronic vehicles unless you know precisely what you are doing.
Frying ECM can be pretty expensive lesson.

DISREGARD-----DISAREGARD
Stupid me---------did not have positive cable making contact with the emergency LUG under sprinter hood. Only one side of positive jumper clamp is hot and it was hung on the PLASTIC Lug protector. The cold side was on the lug.:o
I have it charging properly now.
Thanks and pardon my stupidity.
Marvin




DISREGARD BELOW

Still reading around 5 volts at the sprinter battery Charger didn't seem to help.
Dual battery diesel pickup hooked with cables. Cables making good contact and showing 13.8 volts but the sprinter battery only reads 5 volts.
I'm not sure how the MH battery disconnect switch works but the green light beside it glows regardless of switch position. Switch is a momentary and returns (Spring loaded).
Ignition key will not turn to either ON or Start position.
Marvin

MrWizard wrote:
Jump start with another vehicle
Start generator, use emg jump start along with battery charger

Thanks, will try after charger is on a while longer.
I was surprised the key would not turn the ignition switch.
Marvin

Jump start with another vehicle
Start generator, use emg jump start along with battery charger