Well the 74' is burried under a snow bank until spring. I found that I have no reverse lights, no driverside tail light, no marker lights with the exception of the front passenger marker light and no horn. The interior light connected to the cargo light and cigar lighter keeps blowing fuses, the turn signals obviously blow flasher modules because there is like 8 of them in the glove box, and the hasards only work half of the time. Anyone got recomendations, i've been looking at it off and on because of the cold weather, but can't decide what i should look at first: the wiring, relays, backup switch, grounds etc.

 

Ok look from simple to hard. Trace your wires on the Cargo light/Interior light/cig lighter. Usually there is a short right behind the cig lighter because someone in the past decided to use it as a Radio jump wire. On your exterior lights. Check the bulbs first. that is the easiest. If the bulb is good. Then go into the "I've got juice" mode. Chances are with that many not working it is either a lot of bad bulbs or there is a ground not grounded well enough somewhere.

 

Good to hear from you again, the other day we were wondering where you were as we hadn`t heard from you in a while.
Without seeing the truck it`s hard to tell where to start but here are afew ideas.
Check for a short usually in the rear wiring, this could explain not having any driverside tail light, no reverse lights, blowing the flasher modules and no marker lights. Having no reverse lights could also be a loose connection, burnt out bulbs or a bad switch.
As for no horn it could be a connection or stuck contacts in the horn(s)/ steering column or a bad relay.
It doesn`t really matter where you start though I would start with checking the bulbs and bare wiring first, it`s just a matter of checking untill you find the problems.
Hopefully some more will jump in with more ideas.

 

I just woldn't be to worried bout your backup lghts so many things can trigger them to fail.
Signals if they are all not working would be most likely a "under the dashboard problem"
Remeber Tailights run on one circut and your signal/4way/brake are on another.
The current that runs your passenger side tailight is current from your driverside so the problem is located at the light itself or the rear connection were wires break away to your passenger side

What I find is the best way get a 'current tester tool' and start from the battery testing were your current goes and work your way to the lights following the current/wires

And always remeber Volts tingle, Amps kill.

 

I check bulbs first. The back marker and taillights sounds like the harness is probally chewed up. I know that left corner where the harness has the connections for the back lights gets pretty ratty over time. The wire there tend to get hit by lots of stones and water and if any of it hangs down they get pulled apart and cause shorts back there causing blowing out fuses.
I have had to take the back harnesses out of these trucks and repair them and put back it and either extra tape around the wires or get those plastic harness protectors. Make sure they are tucked back up. Have to use those zip straps to help keep them from hanging. That is where I say most of your back light problems are.
Interior and cargo and light. I would check bulbs then like mossyheart said look at the wire to the lighter. Yes that wire gets used for power to several things radio, accessories like oil gauages ad such.
Horn sounds like a problemin the switch under the steering wheel, but check the horns first. Check the horns by taking a wire from the pos. post to where the horn is plugged in. It should sound off. If they do the horns work. Then check the wires back to the cab and the harness to the steering colunm. Look for breaks or shorts. If none it is the switch area under the steering wheel.
Good luck. Just try and tackle one thing at a time. That way when you succed in the problem working i will make the rest seem easier and you will feel I can do it.