checked the wiring at the lights and chased wire as far as I could through the trunk area, run out of time though any idea where the wire heads from there?
The trunk light harness runs along a channel inside the driver's side rocker panel under the carpet and under two galvanised long narrow plates that protect it. That would also be inside the rear 1/4 interior panel.
2012 Mustang Boss 302 #1918, Competition Orange. FGF replacement 2006 Mustang V6 Pony, Vista Blue. Factory ordered. 2019 BMW X3 (Titled to the wife, but I'm always driving it for her. So I'm claiming it) Old projects, gone but not forgotten: 1967 FB 400, original CA car. After 22 years of work, trashed by the guy who was supposed to paint it. I had to sell it. 1980 Turbo Trans Am 1970 Mustang fastback, 351C 4Bbl, auto 1988 Mustang GT, 5 speed 1983 F-150 4x4, built 302 1994 Chevy K2500 HD 4x4, 454 TBI
So.. I have put a test light in the fuse panel and the fuse holder on the tail lamp side has no power, should this be leading me in a certain direction?
Given your previous description, no power on the tail lamp side of the fuse makes sense... you put in a fuse and it blows immediately. This indicates you have a short to ground somewhere in the tail lamp circuit. The blown fuse isolates the (shorted) tail lamp circuit from the power side of the fuse panel, protecting and preventing the wiring from burning up.
At this point, I would try putting the test light across the tail lamp fuse holder, with no fuse or a blown fuse installed. If the circuit is shorted to ground, the test light should light. (Power supplied from the fuse panel, ground supplied by the short.) Then try taking each of the bulb sockets out of the tail light housing and see if removing any one of the makes the test light go out. Also try disconnecting the license plate wire at the connector near the gas tank filler tube. Hopefully, this will at least allow you to isolate the problem.
I think I gave some poor advice in my previous post about how to isolate the short by removing the bulb sockets. It won't hurt anything if you follow it, but I don't think it will be very productive.
Go to the 1967 Wiring page of the First Gen Site library and examine the 2 diagrams (print both out and piece the halves together). On the diagram, find the orange wire that goes up from the right edge of the fuse block. That is the wire that is supplied by the Stop/Taillamp fuse. If you follow it, it goes to the headlight switch and then to the stoplight switch. The short must be in one of three places: the taillamp circuit, the stoplight/turn signal circuit, or in the fuse panel/dash harness.
To narrow it down, put the test light across the taillamp fuse holder with no fuse installed and verify the test light lights up. Then try unplugging the connector from the stoplight switch (it's the easier one to get to). It's a 2-wire (orange and white) connector going to a switch near the brake pedal arm. If the light goes out, the issue is somewhere in the turn signal switch or turn signal/stop lamp wiring. As an additional test, you should now be able to put a fuse in without it blowing (only while the stoplight switch is unplugged).
If the test light stays on, leave the stoplight switch disconnected for the moment and unplug the connector from the headlight switch. It may be possible to get to it by reaching up from underneath, or you may want to remove the instrument cluster to get better access. If the test light goes out when the headlight switch is unplugged, then the issue is somewhere in the taillamp/license plate lamp wiring. As an additional test, you should be able to put a fuse in without it blowing and you should be able to reconnect the stoplight switch without the fuse blowing.
If the test light is still on with both of those connectors unplugged, then the issue is somewhere in the fuse panel or the dash harness.
Try these tests and report back with what you find out. That will help to narrow down the next steps to find the actual short.
Pete, thank you for you help, you went above and beyond and I am very grateful. The problem was the last owner has done something in behind the dash and when putting it back together had pinched the orange wire running to the brake switch. I found it as my test light brushed against the brake pedal arm and it light up!
