Need help - what are these switches?

[J Miller]

2006 E350 diesel

Can someone help us identify these switches? We had our SMB in for service and a couple of weeks later we found the house batteries completely discharged. The red switch (attached photo) was in the off position. We moved it to the ON position and charged the house batteries using shore power. Everything seems to be working as expected EXCEPT the red switch is backlit and it was never backlit before. We are also unclear what the switch above it does (it is in the off position) and if it has anything to do with the red switch. We assume the red switch is a battery isolator but are unable to find anything in the manuals to confirm this. Hopefully someone can clarify this for us.

 

[Scalf77]

In normal operation the red switch should be in auto. It will light up when the batteries are combined. In the on position it combines them and thus the light will be on. In off the batteries will be disconnected.

The auto mode will connect based on voltage levels of the batteries.

 

[Scalf77]

Link to instructions :https://d2pyqm2yd3fw2i.cloudfront.net/files/resources/instructions/990180180-005.pdf

Link to demo video:
https://youtu.be/crAqboyWV9s

 

[doublevan2]

On my E350 from Fresno - that little black switch turns on my front fog lights - for you ??

 

[86Scotty]

If this is a typical SMB and I'm seeing what I think I'm seeing the switches are under the steering wheel on the panel just in front of your knees. If you can't figure out what the small switch does just pull hard on that panel and pop it off. There are no fasteners on an 06 IIRC and these panels are made to be pulled off for service. In other words, you won't break clips. Just pull it and see if the small switch wiring has anything to do with the battery switch wiring. I seriously doubt it does. Russ/Doublevan is right, usually for aftermarket lights or the like.

:b5:

 

[Twoxentrix]

Russ/Doublevan is right, usually for aftermarket lights or the like.

Could also be a switch which controls 'High Idle'.

 

[hansk-SMB]

On my van, the small switch is a manual override to turn on the backup lights.

Took me a long time to figure that out since I would always check during the day and never thought to look in the back. Plus the wires for it disappeared into the rats maze of other wires.

 

[wackerb]

Combine for start

The small switch could also be an override to connect both batteries for starting if the engine battery is weak. In that case the wires will go back into the isolator. Note: not really needed because you can do the same manually with the isolator.

 

[vandiesel]

My small switch like that turned off the dome lights so you could open doors at night in darkness.

 

[ctb]

OK, JMiller....and the winner is: