I'm not an electrical guru, but here's where I'd start after what you've done so far...
1) You say no power to the switch. Does that mean you've removed the switch, and tested the power leads with a test light or volt meter? If not, that's where I'd start... to make sure you have power actually going to & from the switch.
2) You don't mention the type of slide out you have: Shwintek, cable & pulley, worm-gear, etc. If it's a Schwintek, there's a control circuit board located somewhere on your rig that controls it. Here's a YouTube link to the troubleshooting procedures: