I printed my "data card" for my VIn # WDYPD744965903845.
Included in mine are the following:
580 AIR CONDITIONER,
E2B ADDITIONAL BATTERY FOR RETROFITTED CONSUMER,
E36 CUT OFF RELAY FOR ADDITIONAL BATTERY,
M39 14V/150 A ALTERNATOR
Do you think because I have 580 AIR CONDITIONER, the red wire goes in the slot 4 like just like Table 1 above with an 80 amp fuse.
The "580 Air Conditioner" refers to the (almost standard) FRONT air conditioner, not the one on the roof.
So: No, they did not use Fuse 4 to power that particular AC.
(i don't have a roof-top AC, but i do have a 580 on my datacard, and i'm the bought-new owner)
The "cut off relay" is what i called an "isolation" relay (as does MB at times).
It is not one of the items on the side panel (those two relays are the Yellow in-tank Fuel Pump Relay and the (gray) Starter Relay)
MB put the "additional battery" under the front passenger seat, and i forget if they tucked the relay in there, too, or if it was under the driver's seat ... it will have 4 terminal connections, two with BIG WIRES and two small ones (one of which will be brown).
if so, I do not understand why the red reads coach battery voltage only when engine is running. Note E36. does CUT OFF RELAY FOR ADDITIONAL BATTERY and "isolation relay" mean the same thing?
Yes, as i wrote above E36 and Isolation are the same thing. The fact you're seeing House voltage show up on the fat wire says that the relay is operating properly. If you put that on Fuse 4, you'd be charging your house battery when the engine was running. You'll note that the House voltage (probably) does not appear when the key is merely turned on ... that shows that the E36 is waiting for the alternator to be supplying power (i.e. the "D+" signal is being asserted).
Here is picture of under driver seat.
View attachment 153602
That's not "under" the seat ... that's on the side of the seat pedestal.
I really mean *under* (i.e. pull the cushion and remove the cardboard that's covering the top of the pedestal.
The cushion may have a release lever tucked (almost invisibly) into the front edge of the cushion ... push it sideways and the cushion becomes very easy to remove.
Another fact, The air conditioner has been replace with a Brand that is different from the original. I hesitate to just try the 80 amp fuse without knowing the possible cause of the original failure. Looks like I do have the larger alternator. I value your thoughts. Thank you.
Do you mean that you *do* have a roof-top air conditioner?
Here is the 2006 service manual ... the air conditioner (both front and roof-top) are covered in its wiring diagrams (section 8W)
http://diysprinter.co.uk/reference/2006-VA-SM.pdf
Whatever a 3rd party may have done to your Sprinter, i cannot guess.
Without looking it up, i think MB may actually wire their isolation relay and battery-to-battery connection *without a fuse* ... which is not something i'd recommend.
--dick