Alternator not charging
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New User
Joined: Oct 2012
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Alternator not charging
I have a 66 with a 390 few weeks ago while driving home I noticed my headlights were dimmer than usual and then the truck died. Figured the alternator was bad got a jump start and got her home. Replaced the alternator, battery and fuse regulator just to be proactive but when I tested it I'm not getting over 12 volts I've double and triple checked the wiring still no luck heard it could be bad diode? Does anyone have any ideas for I am a novice mechanic thank you in advance.
Tuned
Joined: Dec 2004
Posts: 340
Likes: 8
From: Rock Hill, SC
Is the voltage regulator good? You can run a jumper from the Batt. terminal on the alternator to the field and see if starts charging. If it does you have a bad regulator or a fuse/broken wire in the circuit.
Lead Driver
Joined: Apr 2011
Posts: 6,399
Likes: 40
From: El Dorado, Arkansas
Make sure your battery cables are good and that you have good connections at each end.
I don't know if you have the old points type regulator or a more modern solid-state voltage regulator (?). Points type will have a thick cover on top of it. The top cover on a solid-state voltage regulator will be about 3/4" thick.
You can take your alternator to the parts store and they will test it for free, to see if it's good.
I was battling the 60 amp alternator in my '69 F-100 --flickering headlights, battery draining. I finally pitched it and installed a Ford 3G 130 amp alternator from a '94 Mustang (wrecking yard donor). My truck no longer has any charging issues. Just at idle, the 3G is putting out 75 amps. I got the alternator, primary alternator wire, 2-plug harness to the alternator, 175 amp mega fuse and two lower alternator brackets from Bumpside trucks with a 300 (to combine into one, longer bracket) for around $50.00.
The 3G alternator has an internal voltage regulator so, the external regulator and associated wiring to it can be done away with.
I don't know if you have the old points type regulator or a more modern solid-state voltage regulator (?). Points type will have a thick cover on top of it. The top cover on a solid-state voltage regulator will be about 3/4" thick.
You can take your alternator to the parts store and they will test it for free, to see if it's good.
I was battling the 60 amp alternator in my '69 F-100 --flickering headlights, battery draining. I finally pitched it and installed a Ford 3G 130 amp alternator from a '94 Mustang (wrecking yard donor). My truck no longer has any charging issues. Just at idle, the 3G is putting out 75 amps. I got the alternator, primary alternator wire, 2-plug harness to the alternator, 175 amp mega fuse and two lower alternator brackets from Bumpside trucks with a 300 (to combine into one, longer bracket) for around $50.00.
The 3G alternator has an internal voltage regulator so, the external regulator and associated wiring to it can be done away with.
Lead Driver
Joined: Jul 2011
Posts: 8,679
Likes: 191
From: On the Edge of the Desert
I did the 3G upgrade after I dropped a wrench and fried my old alternator.
I highly recommend doing it. Very easy swap, minimal wiring involved, cleans up the engine bay. And if you don't need the extra drag of the 130 amp model, there is a 95amp model too.
I highly recommend doing it. Very easy swap, minimal wiring involved, cleans up the engine bay. And if you don't need the extra drag of the 130 amp model, there is a 95amp model too.
Ford Parts Specialist
Joined: Nov 2006
Posts: 88,826
Likes: 785
From: Simi Valley, CA
If the original regulator is still in place, look on its cover to see if it has any dents in it.
The points were notorious for sticking, so people rapped on the cover with their knuckles or screw driver handles in an effort to unstick the points.
Lead Driver
Joined: Apr 2011
Posts: 6,399
Likes: 40
From: El Dorado, Arkansas
1982: FoMoCo replaced the points type regulator with an electronic regulator that has MOTORCRAFT embossed on it.
If the original regulator is still in place, look on its cover to see if it has any dents in it.
The points were notorious for sticking, so people rapped on the cover with their knuckles or screw driver handles in an effort to unstick the points.
If the original regulator is still in place, look on its cover to see if it has any dents in it.
The points were notorious for sticking, so people rapped on the cover with their knuckles or screw driver handles in an effort to unstick the points.
This is all the stuff that was removed when I swapped to the Ford 3G alternator.
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