Was under the dash replacing the flashers with some solid state and came across some unplugged wires. Some of them I was able to track down on here. But these 3 remain a mystery. Figured one of you knowledgeable people here would know right away. Thanks in advance. 1) Round plug Green and Black wires 2)Black plug all black wires 3) Yellow, Red, Blue, Black wires
Agreed with #1 & 2 #3 is the plug for radio power & lighting connection. Radio light was controlled via the dash lights, could be dimmed. These plugs were same in other '70s era passenger Ford products. Trucks could be different. Speaker & radio connectors went back to at least '63 models.
The dark blue with the white trace line is for the ashtray / cigar lighter. The other one I've seen but don't recall what it's for..... all blacks generally were a ground wire.