The brake light on the upper cab is wired directly to the brake light switch, it is powered by a Dark Green wire spliced to the Light Green wire coming out of the brake light switch.
If this brake light comes on you have power at the switch, if not then switch is bad, bulb is bad or you don't have power at the switch.
Power for brake light switch comes from Fuse #13, 20amp, then uses a Light Green/Red stripe wire to the brake light switch
This wire and fuse are "hot at all times" so not powered by ignition switch.
Yes, the brake light power for taillights does go to multi-switch for over ride when turn signal is on, it comes into multi-switch on the above Light Green wire coming out of the brake light switch
Dark Blue/white stripe out of multi-switch is Left Turn/Stop
Brown/Yellow stripe out of multi-switch is Right Turn/Stop
At the bulb socket Left Turn/Stop will be a Light Green/Orange stripe wire
Right Turn/Stop will be an Orange/Light Blue stripe wire
So wiring changes colors going to the back of the truck, at a connector I assume but doesn't show that connector on wiring diagram.
Brown wire is the Parking lights power wire and does not pass thru multi-switch, power comes from Headlight switch
Front turn signals use different wires coming out of multi-switch, and go to Dash turn indicator and front bulbs
Trailer light wiring is fused, #3 and #7 fuses, 7.5amp, are used to pass turn/stop power to the trailer light connector, but these only pass power to connector, tail light power doesn't go thru these fuses.
So if these fuses blow only trailer lights would be effected.
Last edited by RonD; 08-23-2015 at 11:13 AM.