Hey there. Welcome to classicbroncos!
And before I forget, if by any chance your VIN starts with a "P" or a "Q" (after the U15..etc that is) pop over to a thread about those vehicles which were part of the transition between '72 and '73 when so many changes were made.
I'll find a link and post it up, but it was started by Viperwolf1 and is titled "mind your P's and Q's" or something like that.
Ok, now that's out of the way...
It sure sounds like your headlight switch. Do the headlights go out at the same time, or just the other lights?
With the sidemarker lights, it's very common for them to just go out on their own and a good smack with your hand or a quick twist of the socket behind the fender will often have them come back on. So don't necessarily use the side-markers as an indicator of health in the system.
The tail lights could also be a bad wire or connection. The connector on the driver's side of the engine compartment near the firewall is usually good, but can also come loose and get dirty or rusty. The more common ailment is the condition of the wire bundle along the frame. If there was ever a dual exhaust setup installed, they often ran too close to the wires and caused trouble. Also mounting things near there often pinches a wire and things get wonky from there.
So give the wire bundle along the frame a good inspection.
The light to your tachometer could just be a bad connection, as this is not a stock Ford item and was installed sometime after. And who knows how it was done. You'll have to follow the wires on that to find out if it's even connected, or just the bare end of the wire stuffed into an open hole in a connector. Common with tach installs actually.
Might even be the cause of some kind of a short. Not likely, but not impossible either.
Even though this has nothing to do with your lights, pull all the fuses, brush the contacts a bit and put them back in. This usually helps to get the rest of the system working better and doesn't hurt. Or cost anything!
Check your battery negative cable. If it's a single cable to the engine block, with no other wires or connections anywhere, then you need to add a separate wire of about 10ga size from the battery negative to the body. Usually the wheel well at the starter relay/solenoid mounting bolt is a convenient place.
Then, while you're at it, might as well add the one that For should have added when it was built. Make another 10ga jumper to run between the back of the engine and the firewall. You can use the same 10ga wire size, or pick up one of those pre-made braided grounding straps at the local auto parts store.
Pick a convenient bolt on the firewall and clean underneath to get a good connection. Us a convenient bolt on the back of the intake, but not one of the actual manifold-to-head bolts as that could cause a leak.
This added grounding can only help a 44 year old truck that had poor grounds from the factory. Your dash panel counts on being able to get a good ground, and the dash lights are very much effected by this.
Here again, no guarantee that this is your issue, but every EB can benefit from the mods just described.
In fact, the battery cable addition isn't a mod at all, but just putting it back to stock. Most people change the negative cable and lose the original ground connection to the body. Gotta' have it.
Good luck. It's very likely the switch, or rear harness, but wait for a few others to chime in with their recommendations.
Paul
