Hello, I'm new on forums and not too savvy so excuse the lack of know how. I am working on my 1979 f100 I6, no ac, manual 3 speed. I recently replaced the voltage regulator, battery, alternator and all battery cables to include from the starter to the starter solenoid because the truck is not charging. So with that being said I obviously have other issues. I have tested the components individually and determined they are functioning as they should. I have read that fusible links would cause the no charging issue but am at a loss as to the wiring my truck has. It was my understanding that there should be a fusible link between the alternator and solenoid but seem to have more and dont see visible damage. I would greatly appreciate all the help I can get. I have posted pictures of the wiring...

 

I recommend you purchase the shop manuals and the electrical schematics for your truck. You should be able to find them on the internet. It's almost impossible to properly troubleshoot vehicle electrical systems without the schematic diagrams. The diagrams identify the color of each wire, along with where and how they connect. Your truck's wiring looks to be very clean, and that will be a big help. You may need to use a multimeter to measure voltage and/or resistance. It doesn't have to be fancy for basic troubleshooting. It can be analog or digital. Don't be scared to make basic measurements. We're only talking about 12-14 Volts here. Do NOT attempt to make resistance measurements with the battery connected! The Ohmmeter will supply its own power.

Fusible links may not show any visual evidence of having failed. Check them with the Ohmmeter. It will read infinity for an open circuit, and very low (near zero) resistance for a good one. Disconnect one end before measuring.

 

Your fusible links are the red and orange rubber U shaped ones....that even say fusible on them. I can seem them in the pics. And the orange one with a wing on it. Grab a wire on each end of the body and see if they are "stretchy", if they stretch they are bad. That one with the inline glass fuse holder is a PO added one tap in.

Wiring diagrams start on post #10 https://www.ford-trucks.com/forums/1...then-some.html

Normally a faulty voltage regulator or a alternator is the problem , but you have already replaced those parts. But did you get them to bench test the new alternator before you walked out the store...its have been known to happen.

Check for any thing unplugged, not looking to be in good shape, melted wires, blown fuses, ark and spark sign. Was it working and then you worked on it added anything like off road lights or a stereo and then things quite? Hooked up the battery backwards, or a back wards wire jump start attempt?

 

Used OEM Parts Guy, thank you. I will check for the wires to be stretchy. I did not have the parts store check the alternator but I did use a jumper on the voltage regulator harness to test if alternator loaded up to the max output, so I know the alternator is good. Additionally I replaced all battery cables and do not see any wires that are stripped of the sheathing nor that are disconnected. I noticed that the truck wasn't charging after I cleaned and replaced cooling components. (I had the truck running for a while) After about an hour of running the truck it wouldn't start. I went and bought a new battery and verified 12.6 volts by multimeter across the posts put it in the truck and decided to make sure it was being charged. It was not... Being that my electrical experience is very limited I decided to buy the alternator and a new voltage regulator as the truck was previously parked for over 20 years.

 

I have a Haynes manual and have looked at the schematics. I have been able to identify the fusible links, so I suppose my real question is, if I have already replaced the other components should my issue be with the fusible links? I have found no other frayed wires or disconnected wires. Additionally I have cleaned the ground to the block and starter, as well as where the voltage regulator mounts.

 

I am not a real sparky guy either, but I have been known to grab a hot wire every now and again. Sounds like you have al the elec component bases covered.

 

So by that logic I am left with the fusible links as the origin of my issue??

 

keep in mind that even new parts can be bad. Since full-fielding the alt causes it to charge, that proves out several things. If you measured charging voltage at the battery, that proves the fusible link between alt and bat + is fine. I'm guessing bad new regulator or wiring related to the regulator...here is a troubleshooting chart from the factory service manual...

 

Thanks for providing the troubleshooting test from the service manual. I did measure battery and etc.. Below are my results. Keep in mind this is my first adventure with charging systems and any additional tips are greatly appreciated. It is also worth mentioning that I "bench tested" the regulator. I basically ensured that there was resistance at each terminal, not sure how accurate that is...

 

Thanks for providing the troubleshooting test from the service manual. I did measure battery and etc.. Below are my results. Keep in mind this is my first adventure with charging systems and any additional tips are greatly appreciated. It is also worth mentioning that I "bench tested" the regulator. I basically ensured that there was resistance at each terminal, not sure how accurate that is...

 

Well according to the troubleshooting chart "fusible" links are at the top of the list in primary checks. And dlburch says "If you measured charging voltage at the battery, that proves the fusible link between alt and bat + is fine." Time to walk the troubleshooting blocks step by step.

 

So I checked the resistance on the fusible links and all read close to 0, no infinity readings. I also pulled off the connections from the back of my alternator to check for broken, frayed or burnt wires (none found). Additionally I checked resistance from F terminal on voltage regulator harness to ground on alternator and found no issues either. I am at a loss and am unsure about how to proceed.

 

did you follow the troubleshooting steps above? if so, post your results for each step...if not...follow the troubleshooting steps above...

 

I measured 3.8 on multimeter when testing the resistance between F on regulator harness and ground to alternator. This was while truck was not running. I did the same test while running and it measured between 10.2 and 14.3. I did not find any messed up wires and fusible links measured 0.6, 0.7, 0.6.

 

Hey Andy. Follow the heavy black wire off the solenoid , it should come to a 3 way connection. Check this connection out carefully. If it’s not good it will prevent charging. I had this problem on my 1979 F250 4x4 a few years ago.