I'm guessing you're talking about the T1N?
Anybody here that can help me find where to look. I lost speeds 1-3 on the control panel but 4 works. I've had this happen in other vehicles and we have changed out the switch. Is it the same here or am I looking at something bigger?
Sounds like the resistor array part that slows down the fan is disconnected or not in the circuit somehow.
It might be something bigger, but without going into the controls myself, I would only be guessing.
Click here to disassemble part of the dash to get to the heating/cooling controls.
Instructions for disassembling the heating/cooling controls from the dash:
View attachment ac.pdf
In the "OPERATION" section of the above pdf file, it says that if anything is broken in the heating/cooling controls unit, you have to replace the entire unit.
If you're going to have to replace the entire unit, as the service manual recommends, it doesn't hurt to take it apart and try to fix it yourself. Really nothing to lose.
Also, is there a way to change the vents? My employees like to cross their legs in the van and hit the vents with their boot and have broken the slats.

Great forum and thanks in advance.
Are the slats broken or are they just out of their sockets like this...
http://www.sprinter-source.com/forum/showpost.php?p=4546&postcount=4
...if they're actually broken, you will have to go back to the dealer for the entire plastic bezel piece that goes across the dash. Then there's the ebay and junkyard option.