Engine won’t Turn Off!!!
Tuned
Joined: May 2017
Posts: 414
Likes: 40
From: C-town,MD
The diode is a one way electrical switch basically. It's probably bad. I'm pretty sure someone makes a kit for swapping a 3G alternator on our trucks. I put a GM alternator on my truck because at the time the 3G alternator didn't exist
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New User
Joined: May 2020
Posts: 7
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but what would be the point in doing this? It’s not like I need a larger alternator
Lead Driver
Joined: Jul 2017
Posts: 9,577
Likes: 1,161
From: San Jose, CA
Maybe you don't, but the previous owner either felt that an upgraded alternator would be a good idea, or someone convinced them of it. Lots of potential reasons actually.
When I upgraded my original 55a version for a 105a version it still had an external regulator and like in DirtyFerd's case, the 3G was not around yet.
The 100a version was actually an option on some of our trucks too, so it's not like it was not something Ford never imagined. It's a pretty standard practice.
In most cases I'd have to say it's not the extra power of an internally regulated alternator that is desired, but the seemingly simpler wiring. One less component out on the fender, and fewer wires strung around the compartment.
However, the starter cranking when you connected the battery has nothing to do with the alternator. Not unless the wiring is totally butchered.
Power is getting to the Red w/blue wire on the starter relay, or the relay itself is bad.
The alternator feeding back through the Green w/red wire could possibly be doing it, if the diode has gone bad, but only if the ignition switch is bad too. I've installed dozens of 3G's and never added a diode and never had any feedback issues. Might be the way they wired it, or it might still be a problem with the ignition switch and/or it's wiring.
I know you've replaced the relay/solenoid and the ignition switch already, but it's still possible they're faulty.
You might just remove that tape around the diode (or did you do that already and that's how you found it?) and see what's going on there.
If you disconnect the green wire then the alternator will not charge, but you can also test the theory that the alternator is doing something and causing the engine to keep running when you turn off the key.
You might just look for some other oddities in wiring that the PO left you too. Can you post up some more pics, perhaps of the area around the battery and starter relay? Is the old voltage regulator and wiring gone completely? I think your '75 would still have been up by the side of the radiator, correct?
I wonder what other gems the PO has left to surprise you when digging?
Next time you get it running and it won't turn off with the key, pull the small Brown wire off of the starter relay to make sure there is no feedback through that wire to the ignition coil.
Good luck.
Paul
When I upgraded my original 55a version for a 105a version it still had an external regulator and like in DirtyFerd's case, the 3G was not around yet.
The 100a version was actually an option on some of our trucks too, so it's not like it was not something Ford never imagined. It's a pretty standard practice.
In most cases I'd have to say it's not the extra power of an internally regulated alternator that is desired, but the seemingly simpler wiring. One less component out on the fender, and fewer wires strung around the compartment.
However, the starter cranking when you connected the battery has nothing to do with the alternator. Not unless the wiring is totally butchered.
Power is getting to the Red w/blue wire on the starter relay, or the relay itself is bad.
The alternator feeding back through the Green w/red wire could possibly be doing it, if the diode has gone bad, but only if the ignition switch is bad too. I've installed dozens of 3G's and never added a diode and never had any feedback issues. Might be the way they wired it, or it might still be a problem with the ignition switch and/or it's wiring.
I know you've replaced the relay/solenoid and the ignition switch already, but it's still possible they're faulty.
You might just remove that tape around the diode (or did you do that already and that's how you found it?) and see what's going on there.
If you disconnect the green wire then the alternator will not charge, but you can also test the theory that the alternator is doing something and causing the engine to keep running when you turn off the key.
You might just look for some other oddities in wiring that the PO left you too. Can you post up some more pics, perhaps of the area around the battery and starter relay? Is the old voltage regulator and wiring gone completely? I think your '75 would still have been up by the side of the radiator, correct?
I wonder what other gems the PO has left to surprise you when digging?
Next time you get it running and it won't turn off with the key, pull the small Brown wire off of the starter relay to make sure there is no feedback through that wire to the ignition coil.
Good luck.
Paul
Tuned
Joined: May 2017
Posts: 414
Likes: 40
From: C-town,MD
My stock alternator was only like 37 amps. I bumped it up to a 78 with the delco. It's better if you want to upgrade any electrical such as headlights, stereo, or an electric fan. Maybe the voltage regulator went out on the PO and he figured this was an easy upgrade for future projects.
Thread Starter
|
New User
Joined: May 2020
Posts: 7
Likes: 0
Maybe you don't, but the previous owner either felt that an upgraded alternator would be a good idea, or someone convinced them of it. Lots of potential reasons actually.
When I upgraded my original 55a version for a 105a version it still had an external regulator and like in DirtyFerd's case, the 3G was not around yet.
The 100a version was actually an option on some of our trucks too, so it's not like it was not something Ford never imagined. It's a pretty standard practice.
In most cases I'd have to say it's not the extra power of an internally regulated alternator that is desired, but the seemingly simpler wiring. One less component out on the fender, and fewer wires strung around the compartment.
However, the starter cranking when you connected the battery has nothing to do with the alternator. Not unless the wiring is totally butchered.
Power is getting to the Red w/blue wire on the starter relay, or the relay itself is bad.
The alternator feeding back through the Green w/red wire could possibly be doing it, if the diode has gone bad, but only if the ignition switch is bad too. I've installed dozens of 3G's and never added a diode and never had any feedback issues. Might be the way they wired it, or it might still be a problem with the ignition switch and/or it's wiring.
I know you've replaced the relay/solenoid and the ignition switch already, but it's still possible they're faulty.
You might just remove that tape around the diode (or did you do that already and that's how you found it?) and see what's going on there.
If you disconnect the green wire then the alternator will not charge, but you can also test the theory that the alternator is doing something and causing the engine to keep running when you turn off the key.
You might just look for some other oddities in wiring that the PO left you too. Can you post up some more pics, perhaps of the area around the battery and starter relay? Is the old voltage regulator and wiring gone completely? I think your '75 would still have been up by the side of the radiator, correct?
I wonder what other gems the PO has left to surprise you when digging?
Next time you get it running and it won't turn off with the key, pull the small Brown wire off of the starter relay to make sure there is no feedback through that wire to the ignition coil.
Good luck.
Paul
When I upgraded my original 55a version for a 105a version it still had an external regulator and like in DirtyFerd's case, the 3G was not around yet.
The 100a version was actually an option on some of our trucks too, so it's not like it was not something Ford never imagined. It's a pretty standard practice.
In most cases I'd have to say it's not the extra power of an internally regulated alternator that is desired, but the seemingly simpler wiring. One less component out on the fender, and fewer wires strung around the compartment.
However, the starter cranking when you connected the battery has nothing to do with the alternator. Not unless the wiring is totally butchered.
Power is getting to the Red w/blue wire on the starter relay, or the relay itself is bad.
The alternator feeding back through the Green w/red wire could possibly be doing it, if the diode has gone bad, but only if the ignition switch is bad too. I've installed dozens of 3G's and never added a diode and never had any feedback issues. Might be the way they wired it, or it might still be a problem with the ignition switch and/or it's wiring.
I know you've replaced the relay/solenoid and the ignition switch already, but it's still possible they're faulty.
You might just remove that tape around the diode (or did you do that already and that's how you found it?) and see what's going on there.
If you disconnect the green wire then the alternator will not charge, but you can also test the theory that the alternator is doing something and causing the engine to keep running when you turn off the key.
You might just look for some other oddities in wiring that the PO left you too. Can you post up some more pics, perhaps of the area around the battery and starter relay? Is the old voltage regulator and wiring gone completely? I think your '75 would still have been up by the side of the radiator, correct?
I wonder what other gems the PO has left to surprise you when digging?
Next time you get it running and it won't turn off with the key, pull the small Brown wire off of the starter relay to make sure there is no feedback through that wire to the ignition coil.
Good luck.
Paul
thanks man I really appreciate it. I will give this a try and see what happens
Junior User
Joined: Jan 2020
Posts: 66
Likes: 3
If you are still having this issue, unhook your battery completely. Go to your starter solenoid, unhook the wire that is on the opposite side of where your positive wire is attached possibly is brown, this should be your wire from the ignition. Make sure you cover the end with either tape or something to protect it. Install both battery cables. Let me know what happens. I can tell you exactly what it is based on the results. It may try to start, if so, easy fix. If it doesn't, well... Let's hope it does, but I do know what that can be as well.
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