Hello- Desperately needing help with a wiring issue. We have a 1964 F-100. We went to start the truck on Friday and clicked the key to the start position, the oil light came on, the generator light was on- went to crank it and heard a loud pop under the hood. We then tried starting the truck again- no lights on the gauge cluster, no anything. We changed out the starter solenoid- didn't fix the problem. We then changed out the ignition switch. Bingo- the lights came back on the gauge cluster- went to crank it- same lout pop out under the hood. Since then- we have changed the starter solenoid, the ignition switch and the headlight switch. We can't get it do anything.

After much wire chasing- every time the black wire with a green stripe that connects onto the accessory post on the back of the ignition solenoid is connected and we turn the key to accessory or start, we lose all power to the starter solenoid. Removed all fuses- checked continuity of wires to fuse block- all good. All fuses are good. For some reason- black wire with green strip shows continuity if you go from eyelet to ground- any ideas??

Looking for a wiring diagram for the junction block that connects to the back of the headlight switch. And looking for any advice that anyone may have to fix this issue.

 

Sounds like bad connections on the battery cables or the cable from the start relay to the starter. Take them all off and clean them up. If they have brittle insulation or green stuff in the cables replace them.
Make sure you have a good ground to the engine and a ground from the engine to the cab.

 

Sounds like a short. Check the BLK/GRN wire to see if it is grounding, perhaps where it runs through the bulkhead.

 

We checked that and even with the key off- it was still showing 12v. We traced it to behind the dash and it connected into one of the lights in the back- the bulb had corroded and come apart in the socket. Took bulb out.

 

You need to learn how to conduct "Voltage drop test" on a loaded circuit.. stop guessing

 

12V can easily show up on cables / connections that are loose or worn and won't carry enough current to engage the starter. I've had that 'pop' due to poor connection at the battery. Do what Crop Duster said

 

I agree with @Mannie. In this case to see if the BLK/GRN wire is shorting out to ground you wouldn't generally check voltage. What I'd do is disconnect the battery and remove the BLK/GRN wire on the back on the ignition switch and then check from the ring terminal to ground for continuity. If there is continuity, then I'd pop out that fuse and do the exact same check. If continuity to ground goes away, then you know that after the fuse - the wire makes contact with ground when it shouldn't. If after pulling the fuse the problem remains with the continuity to ground, then likely something in the fuse block itself.

If you instead believe that it is shorting to another hot wire then you can do the same continuity checks between the BLK/GRN wire and any of the other wires. The more you can remove from the circuits as you are checking them the easier it will be.