The third brake light has a different circuit path that does not pass through the MF switch. Its a second white wire out of the brake pedal switch (there are three: brakes, third brake, cruise). I would start by probing all three white wires right after the brake switch and see if you get 12v during a pedal press. It might be three wires at the switch or it might be a junction block soon after the switch.

George

 

Thanks, that was some good information I'm glad I know that now. I'll be checking that light out this weekend.

 

May the force be with you.

George