Alternator or Voltage regulator
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Laughing Gas
Joined: Jun 2016
Posts: 892
Likes: 233
From: Kattarp, Helsingborg, Swe
Alternator or Voltage regulator
I was out driving the other day, running some errands, when I noticed that my pickup didn’t have the normal “pepp” in the starter. I suspected it wasn’t charging, but I didn’t have anything with me to confirm. I made it home, but when I tried starting it again, it wouldn’t turn over. I checked the battery, and it was at about 9 volts. I put it on charge over night, and she started right back up, but checking the voltage it only reads about 12.5 volts and it’s declining as it’s running.
now, how do I check it it’s the alternator or the voltage regulator, or something else?
now, how do I check it it’s the alternator or the voltage regulator, or something else?
Cargo Master
Joined: Mar 2008
Posts: 2,569
Likes: 207
From: Washington
Here's good info on doing a full field test from 1TonBaseCamp
https://www.ford-trucks.com/forums/1...regulator.html
If the alternator is bad you should consider doing a 3G conversion. It might be cheaper to get a brand new 3G alternator than a very old 1G alternator that's been rebuilt so many times. Be careful when shopping as some are "compatible" with a 1G, but not really a 1G alternator.
I got my 3G at a junkyard. But if I was buying new I would research a small case 95 amp 3G alternator. Seems more practical for most folks. The junkyard did not have any of these when I was buying mine. I am not sure if the small case 95 amp cost more.
The large case would be available anywhere, so you could do a parking lot repair, compared to something that needs to be shipped. I am not a fan of one wire alternators, plus a replacement would require shipping.
The original 1G is a solid and reliable alternator. But the 3G is a giant leap forward in technology and power output. It really just comes down to what you needs are, or what your future needs will be.
Jim
https://www.ford-trucks.com/forums/1...regulator.html
If the alternator is bad you should consider doing a 3G conversion. It might be cheaper to get a brand new 3G alternator than a very old 1G alternator that's been rebuilt so many times. Be careful when shopping as some are "compatible" with a 1G, but not really a 1G alternator.
I got my 3G at a junkyard. But if I was buying new I would research a small case 95 amp 3G alternator. Seems more practical for most folks. The junkyard did not have any of these when I was buying mine. I am not sure if the small case 95 amp cost more.
The large case would be available anywhere, so you could do a parking lot repair, compared to something that needs to be shipped. I am not a fan of one wire alternators, plus a replacement would require shipping.
The original 1G is a solid and reliable alternator. But the 3G is a giant leap forward in technology and power output. It really just comes down to what you needs are, or what your future needs will be.
Jim
Logistics Pro
Joined: Jun 2003
Posts: 3,921
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FWIW, a charging system will not charge a dead/junk battery.
Pull the plug off of the regulator, jump the A and F terminals, start the engine and measure voltage at the battery. This jump method bypasses the regulator and the alt should produce wide open voltage. This will let you know if the alternator is good.
You may still need further investigation but this will eliminate a bad alternator.
Pull the plug off of the regulator, jump the A and F terminals, start the engine and measure voltage at the battery. This jump method bypasses the regulator and the alt should produce wide open voltage. This will let you know if the alternator is good.
You may still need further investigation but this will eliminate a bad alternator.
Thread Starter
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Laughing Gas
Joined: Jun 2016
Posts: 892
Likes: 233
From: Kattarp, Helsingborg, Swe
It seems that the alternator is not putting out any voltage. It is over 50 years old, so maybe no wonder… the regulator has been replaced at some point in the past, but who knows when. I’m sort of infavor of keeping things as original as possible (also a stingy booger), so I am going to first try and replace the brushes and see if that wakes the alternator. If that doesn’t work, then I’ll look into replacement with something else.
Cargo Master
Joined: Mar 2008
Posts: 2,569
Likes: 207
From: Washington
It seems that the alternator is not putting out any voltage. It is over 50 years old, so maybe no wonder… the regulator has been replaced at some point in the past, but who knows when. I’m sort of infavor of keeping things as original as possible (also a stingy booger), so I am going to first try and replace the brushes and see if that wakes the alternator. If that doesn’t work, then I’ll look into replacement with something else.
I prefer to rebuild my own stuff, as then I know the history. Buying overhaul or rebuilt often means just getting someone else headaches. The overhaul part might only have new brushes swap in, which is something you can do yourself.
Thoughts:
If the brass part, where the brushes ride, is worn, you won't get full life out of the rebuild, but I would still run it as is.
Look for rub marks, rotor to stator. Rubbing means it wont work.
After you're done, take it to an auto parts store and have it tested. This will tell you if all the diodes are good.
From a cost point of view, I would also stop at brushes, unless you want to keep original parts on your truck.
Good luck, Jim
Last edited by JimsRebel; Jan 11, 2026 at 09:24 AM.
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