Alt light on/off
Posting Guru
Joined: Nov 2004
Posts: 1,137
Likes: 2
From: Asheville, NC
Have you got a volt meter? Have you got +12v at the big red wire on the alternator?
When the truck is not running, you should have around 12.6v across the battery.
When the truck is running at 1000 RPM or so, you should read 13-14 volts across the battery if the alternator is producing.
If you dont have power at the big red wire, you have a burned out fuse link, or possibly, you have wired the alternator to the starter side of your solenoid.
Check this all out, and be sure.
After it's all over, you will have fixed it yourself. Makes you feel good.
Best of luck.
When the truck is not running, you should have around 12.6v across the battery.
When the truck is running at 1000 RPM or so, you should read 13-14 volts across the battery if the alternator is producing.
If you dont have power at the big red wire, you have a burned out fuse link, or possibly, you have wired the alternator to the starter side of your solenoid.
Check this all out, and be sure.
After it's all over, you will have fixed it yourself. Makes you feel good.
Best of luck.
Senior User
Joined: Nov 2011
Posts: 261
Likes: 1
From: Colorado Springs
Heres the wiring as per my Ford truck manual, on the back of the alt. you should have the White with Black stripe going to the post marked STA at the top of the alt. The Black with Yellow stripe to the BATT. post about the 3 o'clock position. The White going to the post marked FLD,just inboard toward the center from the BATT. post, That leaves the Black with Red stripe going to the ground post at about the 4 o'clock position.
That ground goes from the alt to the engine usualy at the lower alt bracket. When you say the red lead I assume thats the one marked BATT. so that would be a good place measure the voltage. What rpm is your truck idling at ? What is the voltage on your battey when the the truck isn't running and how long ago was it new as they will loose charge after a while in my experience. A fully charged battery will read 12 volts but I'm pretty sure you knew that LOL. Just so you know alot of us feel your pain chasing the gremlins the pop up on our trucks and challenge our patience,skill and wallets.
That ground goes from the alt to the engine usualy at the lower alt bracket. When you say the red lead I assume thats the one marked BATT. so that would be a good place measure the voltage. What rpm is your truck idling at ? What is the voltage on your battey when the the truck isn't running and how long ago was it new as they will loose charge after a while in my experience. A fully charged battery will read 12 volts but I'm pretty sure you knew that LOL. Just so you know alot of us feel your pain chasing the gremlins the pop up on our trucks and challenge our patience,skill and wallets.
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Junior User
Joined: Dec 2011
Posts: 80
Likes: 0
Battery reads 12V when truck is off. from what your explaining about wiring, I beleive its wired up correctly. Truck is idle around 700 rpm. but I have been checking it at higher rpm and only 12.5 is coming off when running.
When you rev the engine the ALT light inside goes out, then comes back on when truck goes back to idle. wierd. I have not been able to check Volt Meter when rev'd up cuz I'm the only one working on it. Need to have the wife come out and help me...
When you rev the engine the ALT light inside goes out, then comes back on when truck goes back to idle. wierd. I have not been able to check Volt Meter when rev'd up cuz I'm the only one working on it. Need to have the wife come out and help me...
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Junior User
Joined: Dec 2011
Posts: 80
Likes: 0
Ok, reviewed wiring from above post (thanks! that helped!) BUT it did nothing. I had it wired right.
SO started taking off the tape on the wiring harness. MAN.. what a mess. SO am in the process of slicing in new wire for now to make it work. Then I'm going to but a wiring harness. But before that, going to check to see if any wires are grounding out. I have a feeling the person who owned in in AZ cobbled the wiring good. Might as well get started on a re-wire sooner then later.. Bummer.. not the plan, but thats always how it goes...
Thanks again for all the help guys. Appreciate you a ton...
SO started taking off the tape on the wiring harness. MAN.. what a mess. SO am in the process of slicing in new wire for now to make it work. Then I'm going to but a wiring harness. But before that, going to check to see if any wires are grounding out. I have a feeling the person who owned in in AZ cobbled the wiring good. Might as well get started on a re-wire sooner then later.. Bummer.. not the plan, but thats always how it goes...
Thanks again for all the help guys. Appreciate you a ton...
Senior User
Joined: Dec 2010
Posts: 400
Likes: 0
Well? Keep us posted on your progress and what you find out as it will be valuable info for someone in the future!..Good luck! PS, we feel your pain...lol.
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Posting Guru
Joined: Jan 2011
Posts: 1,670
Likes: 8
You could also make it simple and go to a 'one' wire internally regulated alt. Thus taking the original regulator out of the loop. BUT, than you would never know what the problem was and something you would always wonder about. It would most likely keep you up nights for years...... ;o) Doesn't mean you couldn't go back to the original one later down the road.
Posting Guru
Joined: Nov 2004
Posts: 1,137
Likes: 2
From: Asheville, NC
Personally, I dont want a GM alternator on my Ford.
Before I get hit with insult replies, I have 2 GM cars with this fine internally regulated alternator on them. Both are OEM units, and have been rebuilt: brushes and bearings, TWICE in the last 25 years. They are flawless. But, they arent on a Ford.
Has anybody reading this got a copy of the schematic for the alternator wiring harness that they can send to the OP, here? It's not that hard.
BTW: did you double check the connectors that the regulator attaches to? Doesent take much corrosion to make a bad connection there, either.
Before I get hit with insult replies, I have 2 GM cars with this fine internally regulated alternator on them. Both are OEM units, and have been rebuilt: brushes and bearings, TWICE in the last 25 years. They are flawless. But, they arent on a Ford.
Has anybody reading this got a copy of the schematic for the alternator wiring harness that they can send to the OP, here? It's not that hard.
BTW: did you double check the connectors that the regulator attaches to? Doesent take much corrosion to make a bad connection there, either.
Posting Guru
Joined: Jan 2011
Posts: 1,670
Likes: 8
This is true about corrosion. I think he mentioned cracks along the wire. Corrosion could have set in anywhere along that wire which would impare load carry. Possibly lay in some new wire temp to see if the problem goes away. If it does, wire can be made more permanent. I agree, GM product is not Ford. I just know some guys here have talked about doing it. Wish I were closer to help.
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Junior User
Joined: Dec 2011
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WOW, duginto the wiring on this. what a train wreck! some wires were just held together with elec tape. then the main black and yellow wire coming from cab were put together with a bolt, washer and nut combo with tape around it -(hillbilly). Its such a mess what is put together I dont know where to start.
Has 2 blck & Yell wires from cab to the bolt and wash. then the yellow wire from regulator to the bolt also. then another yellow wire from regulator harrness spliced into the wire going to the alot, which is also attached to the bolt,washer and nut combo. - What a mess.
does anyone know what wires should go where? should they all be connected together like that?
Has 2 blck & Yell wires from cab to the bolt and wash. then the yellow wire from regulator to the bolt also. then another yellow wire from regulator harrness spliced into the wire going to the alot, which is also attached to the bolt,washer and nut combo. - What a mess.
does anyone know what wires should go where? should they all be connected together like that?
Logistics Pro
Joined: Feb 2000
Posts: 3,565
Likes: 9
From: Sun River St. George
Alternator
OKAY! I think it is time for you to re-evaluate your situation. 45yo + wiring that has been jerry rigged, an electrical issue that is keeping you from operating your truck, time and money spent without positive results. You can easily install a FORD 3g one wire 100 amp alternator that will solve the charging issue permanently. The cost is in the neighborhood of what you are spending on your current system, will yeild positive results and get you back on the road. You can do this yourself and likley get your money back on the alt and regulator you already bought. I'd ask my parts guy for a remanufactured 3G Ford alternator then go here for a diagram http://i3.photobucket.com/albums/y99...lternator.jpeg or google 130 AMP Alternator Installation for 1965 Mustang. You can also do the cheeeveey deal, just don't get all choked up about Delco parts. Universal wiring harnesses are all over ebay and trucker magazines for cheap. I'd put one of those in your future. IMHO!
Posting Guru
Joined: Nov 2004
Posts: 1,137
Likes: 2
From: Asheville, NC
First, was this alternator ever really working and charging a battery?
I need to have a look at the charging system on his model truck. There may be a connection for 12v at the ignition switch when turned on that might be disconnected.
Sometimes this 12v supply excites the alternator. I like excited alternators.
I need to have a look at the charging system on his model truck. There may be a connection for 12v at the ignition switch when turned on that might be disconnected.
Sometimes this 12v supply excites the alternator. I like excited alternators.
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Junior User
Joined: Dec 2011
Posts: 80
Likes: 0
Ok, went to bone yard that I just learn about hear in northern MN. Guy had 9 1966 Custom Cab trucks sitting around. Found lots of parts I was going to buy! One truck had the correct cabling harness. I followed all wires to see how they were hooked up. Also robbed a close to mint dash bezel with all the gauges. Just got done taking it apart and cleaning it all up.
Spliced all wires and have alt back together. Just need 2 more connections for wires and will put back together and fire it up.
Also found wiring diagram on web and printed.
I'm excited to get back to this bone yard. These truck are barley robbed. 3 had perfect glass in them. One truck only had 32k on it. front end smash. the rest was in good shape. Sweet!
thanks all!
Spliced all wires and have alt back together. Just need 2 more connections for wires and will put back together and fire it up.
Also found wiring diagram on web and printed.
I'm excited to get back to this bone yard. These truck are barley robbed. 3 had perfect glass in them. One truck only had 32k on it. front end smash. the rest was in good shape. Sweet!
thanks all!