Trucks together....couple of electrical issues looking for advice on.

[jaredts]

The brake light on the dash comes on either with the parking brake applied via a switch there, or if the wire to the combination valve is grounded.  If plugging in the combination valve makes the light come on than its probably doing its job--warning you that either the front or rear circuit has lost fluid pressure.  The other possibility is that the spool in the valve is seized to one side.  You need to do some brake troubleshooting as I wouldn't personally disable that safety feature.

[ralphhemi]

 More than  likely its a bad ground in the park and turn signal socket, i have also seen a bad bulb where one of the filaments brake off and ground to the other filament.

[bake74]

     banshee58316, I saw that was your first post, welcome to the site.