-1978 F100, 2wd, 6 cylinder, manual transmission

Headlights don't work, interior lights don't work, won't start, completely dead.

I'm not very good at truck repair, but I thought I would try to fix the truck myself.

Got the battery charged, replaced the positive battery cable, ran wire brush over both battery terminals, ran wire brush over negative battery cable connection to engine block, ran wire brush over engine block connection with negative battery cable, ran wire brush over bolt connecting negative battery cable to engine block, replaced starter, and replaced voltage regulator(Autozone employee suggested this). Still won't start, still completely dead.

Searched the internet and thought that maybe replacing the fusible link would fix the problem. Removed the fusible link wiring(a picture is here: ). There is a wire that connects into the voltage regulator that appears to become one with the fusible link(there is a rubber tab that both the voltage regulator wire and the fusible link join into). On the one end of the fusible link after the rubber tab, there is only wire exiting the rubber tab. On the other end of the fusible link before the rubber tab, the fusible link and the wire running to the voltage regulator are separate.

How do I replace the fusible link, do I have to replace each and every one of wires shown in the picture above? Can I go to an auto parts store and get all of the above wires? Or can I somehow separate the fusible link from the wire running to the voltage regulator where they join at the rubber tab?

Any help is greatly appreciated.

 

The harness in the picture is called the alternator wiring harness.
The wire that is the fusible link is easy to test. Grasp the wire and tug on it. If it streches or feels spongy then it's bad and needs to be replaced.
Only the fusible link needs to be replaced, not all of the wires.
The link is more than likely a 16 ga. You can get these from the parts store. Cut out the old piece. The correct way to install the new link is to solder the joints and cover them with heat shrink tubing but regular crimp on butt connectors will work too.

 

Thanks for the reply. I replaced the fusible link, still completely dead. Could the solenoid be bad? Any other ideas?

 

Invest in a test light or multi-meter and start at the battery checking for voltage. A wiring schematic would be helpful, but essentailly you need to progress to the fusebox in the cab and find where the interuption is.

It could also be the cab ground as well. Make sure there is a clean ground path from the cab (under the cowl) to the engine and from the engine to the battery.

 

Does that mean you pulled the terminals, wire brushed the posts, wire brushed the inside of the terminals & clamped them tight?

Also... When you had the battery charged; how long before you tried using it? Did they load test it or just charge it?

Sounds like a bad/dead battery or bad connections. Somethings not right.... Try another "known good" battery and work from there.

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Just to be sure, I replaced the negative battery cable, I replaced the solenoid, and I replaced the cable running from the solenoid to the starter. I thorougly ran a wire brush over the engine block connection with the negative battery cable, I thoroughly ran a wire brush over both ends of the positive battery cable, I brushed the battery posts thoroughly again, I tightened the cable connections with the battery posts, and the battery is reading 12.4 on the multimeter.

The negative battery cable connection with the engine block is dirty, but I don't know how to get that cleaner. Maybe I need to buy some cleaner.

I don't think I'll be able to test back to the cab for a short as I don't know how to do that.

I will take the battery back to Autozone and get them to load test it. Maybe I'll buy a new battery just to see if that is the problem.

Am about ready to give up, I don't have any other ideas.

 

Just to be sure you have the power connections correct on the solenoid. Take a look at this link: Ford Truck Enthusiasts Forums - View Single Post - Need help Hooking starter back up

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Thanks for the assistance.

Yes, the connections on the solenoid are the same as that link.

I believe that I am getting continuity on the multimeter at the starter. One multimeter probe was on the cable connection at the starter for the cable running from the solenoid to the starter. The other probe was on the body of the starter. The ohm reading on the multimeter is reading 0. The multimeter reads as open loop with the probes not touching anything, so I believe there is continuity at the starter.

 

So you have a multimeter. Put it on DC volts, the negative lead on ground and start moving the positive lead.

 

Don't just start buying parts and hope you luck out and buy the right one. That's called "Easter Egging", and it can get very expensive. Since you have a multimeter, start at the battery and measure post to post. !2V or more should be fine. Now, leaving the meter lead on the positive terminal, test to any engine ground. You should have the same voltage. Work your way with the negative meter lead all the way to the starter. Any voltage drop means you have a poor ground connection. After you have tested the negative (ground) side to engine, starter, body, etc. and have no voltage drop, then do the same with the positive meter lead. Leave the negative lead on the battery and measure voltage at the starter (big wire), fuse block (some will have voltage and some will not until the key is turned on). Do your headlights come on? If not you likely have a bad ground somewhere. If NOTHING is working, there aren't many places that could be the problem.. Most often it is a bad ground, not a bad positive circuit. Just go one step at a time and make sure each leg of your journey gives you the same voltage.

After you're all done with this part, try turning on the headlights. If they come on, measure the voltage with them on. It shouldn't drop much. Then try the starter. If voltage drops way off and the starter doesn't turn, you have a bad connection or a bad starter. You should hear the starter solenoid click loudly. If not, you have a problem with the ignition switch, start relay or solenoid. Electricity is not a mystery, you just have to be thorough. Start at the source (battery) and end at the device you are trying to power.

It seems easy when you've been an electrician for 40+ years (like me) but the bottom line is finding where you are losing the voltage. A wiring diagram is very helpful, but can be confusing until you get the hang of it. The object is to get power where you want it when you want it. Lights first, ignition second, starter third, everything else last.

 

Just want to stress that I am an absolute beginner at this, no experience at all.

Battery dc voltage is measuring 12.38.

I put the positive multimeter lead on the positive post of the battery. I put the negative multimeter lead on the body and got 12.38, on the engine block and got 12.38, on the starter and got 12.38, and on the negative cable of the solenoid and got 12.38.

You say do the same with the negative lead. I don't know what this means? Put the negative lead of the multimeter on the negative post of the battery? I did that and put the positive lead of the multimeter on the body/engine block/starter/positive cable of solenoid and I get a reading of 0 volts.

Nothing is working. No headlights, no interior lights, won't start.

 

I put the negative lead of the multimeter on ground and the positive lead of the multimeter on the positive battery post and got 12.38. I put the negative lead of the multimeter on ground and the positive lead of the multimeter on the engine block and got 0. I put the negative lead of the multimeter on ground and the positive lead of the multimeter on the starter and got 0. I put the negative lead of the multimeter on ground and the positive lead of the multimeter on the positive cable of the solenoid and got 12.38.

 

Maybe not the answer, but advice all the same.

Have you enlisted any assistance from you STATE chapter? I am sure there are fello FTE members that can help and maybe a phone call is all it takes. Hit up your state chapter and get some local advice.

I have in state FTE guys helping me and we all get together and wrench fest a rig ever now and then.

Out last group project was a 4' lift on my F250.

Stay with it and stay motivated, its got to be a wiring issue, hang in there.

 

I don't know where the contact information is for in-state(Cincinnati, Ohio)FTE members?

Maybe it is the main battery fuse, I didn't think of that. There are several wires running into a box on the driver's side front fender wall. Am going to try and open up that box to see what is in there. Don't know where(or if)there is an engine fuse box. There is a fuse box located underneath the steering wheel(sort of)above the brake and gas pedals. I looked at that, but there is nothing on there related to the battery, just the radio and other interior-related things I think.

 

Put in a new battery(which I will return since the battery is not the problem)reading 12.74, and still won't start. Will check the fuse box under the steering wheel again. The box on the driver's side fender was just a housing for a connector that some wires ran into, no fuses inside that box.