Disconnect all power sources before proceeding

Wait until complete night or cover your panels with an opaque material. Any sunlight that touches the panel can generate voltage and cause bodily harm. 

Electricity can be very dangerous. Installation should be performed only by a licensed electrician or qualified personnel.

Steps

1. Turn switch to OFF
2. Use an open-end wrench (13/16" or adjustable) to loosen the top cable glands
3. Use a Philips screwdriver to loosen the cover screws and remove the cover
4. Use a Philips screwdriver to loosen the top terminal screws labeled 1 & 3
5. Pull wires out of terminals and through cable glands
6. Insert the wires into the opposite cable glands (red to terminal 3 and black to terminal 1)
7. Tighten the screw terminals
8. Tighten the cable glands
9. Repeat stems 1-9 on the other switch
10. Turn switches to ON

 It is easier to switch the wires at the battery.