Brakes on 2001 Chevy Silverado HD

Help!  Recently, while towing, brake light came on.  I checked and my rear wheels were so hot I could not touch them.  After getting home, I have replaced brake pads, rotors, and calipers.  Bled brakes.  Wheels cool now, but light will not go out.  Took Truck to local mechanic.  He said to replace the switch under the brake fluid reservoir.  Brake light is still on. Now, what do I do?  I have been trying to find a repair manual for my truck and can not find one for 2500 HD.  Is there a trick to getting the light to go out?  Is there a special sequence to bleeding the brakes?  What about the proportion valve or the master cylinder.  I have always done all of my own repair work, but this one stumps me.

Have you tryed to disconect the battery and see if the light comes back on?

Tried that and it did not work.  Thanks!