Yo rswanson78,
Welcome!
Wiring Diagram in a 78 & 79;
by Ford by Topsig (Ziggy)
Also shows ground is y supprt under dash.
MIESK5 NOTE, The 78-79 TG ckt included a 20 amp Circuit Breaker @ starter relay & also receives 12 v from Ignition Switch;it is behind gauges/speedometer.
Try pushing on tailgate in center and if no go, on both sides in case the striker bushings are worn, etc.
Latch Safety Switch (also ref to as Limit Switch or Interlock Switch); "... Miesk5 Note; In 78-82, both latches have to be closed since the interlock safety switch is mounted in the center mechanism; & their strikes that mount to the body can be interchanged with some effort. The safety switch was moved from the center (tailgate handle) to the left latch by 1983 by Seabronc (Rosie, Fred W)
Latch Parts Break-Out Diagram in 78-79 - #1
Source: by Jeff's Bronco Graveyard
http://web.archive.org/web/20140826125117/http://broncograveyard.com/images/addon/79tailgateltchrods.jpg
"...If the glass is clear of the shell, but you can't open the t/g, remove the inside access panel & pull the 2 rods (described as Link in above diagram )inward. Either unclip them from the center mechanism, or pull them like bow strings to release each latch. Make sure the glass isnt so high that it engages the campers groove, or it could break. If it wont come down, unbolt the slides from the glass, or the motor from the regulator to lower the glass..." Miesk5 Note, the bars are referred to as the Link(s) in most 78 to 79 diagrams
