alternator/charging, need help quick!!!!!
Junior User
Joined: Mar 2001
Posts: 79
Likes: 0
From: Granger, IA
alternator/charging, need help quick!!!!!
I've got a 76 f150 with a 390 in it and while i was driving down the highway yesterday it started to die. To make this story short, i figured out that if i turned the radio, headlights and blower motor off it would run fine. So i put a new alternator and regulator in and it would run fine with any accesory turned on, problem is, the battery wouldn't charge back up after starting. I messed around in the electronics for awhile and got it to run fine and charge, but it has in the course of a few hours gone back to stumbling down the road with any electrical equipment on AND the battery won't charge. What did I screw up now?
New User
Joined: Jan 2008
Posts: 0
Likes: 24
alternator/charging, need help quick!!!!!
Do you have a volts/ohms meter?
You need one.
Set it at 20v DC setting.
Attach it to the battery leads and start the engine.
If the meter reads about 12v at idle, then when you rev the engine up the meter goes to say 15.5 volts,the alternator and voltage regulator are working.
Do you have a battery charger?
Yes, Use it to *fully charge* the battery and take it to an auto parts house to have them check its condition (free of charge, btw)
Dennis https://www.ford-trucks.com/user_gallery/sizeimage.php?&photoid=1733&.jpg
[i][font color=red]Calgary,Alberta,Canada[/font][i]
https://www.ford-trucks.com/user_gallery/sizeimage.php?&photoid=3140&.jpg
http://community.webshots.com/user/mil1ion
[font color=green] Please Don't Ask Me Any Tough Questions,
"I'm Saving My Memory For When I Develop Alzheimer's" [/font]
[font color=blue]78 F-150 429CJ,Silver,Explorer Pkg.
641/2-Mustang 260,Pre-World's Fair Car.
64-Fairlane500 S/C waiting for a 390-4spd.
68-Mustang 289-Sunlit Gold 80,892Mi
78-Buick LeSabre 403 4V
84 Volvo DL Wagon [/font]
You need one.
Set it at 20v DC setting.
Attach it to the battery leads and start the engine.
If the meter reads about 12v at idle, then when you rev the engine up the meter goes to say 15.5 volts,the alternator and voltage regulator are working.
Do you have a battery charger?
Yes, Use it to *fully charge* the battery and take it to an auto parts house to have them check its condition (free of charge, btw)
Dennis https://www.ford-trucks.com/user_gallery/sizeimage.php?&photoid=1733&.jpg
[i][font color=red]Calgary,Alberta,Canada[/font][i]
https://www.ford-trucks.com/user_gallery/sizeimage.php?&photoid=3140&.jpg
http://community.webshots.com/user/mil1ion
[font color=green] Please Don't Ask Me Any Tough Questions,
"I'm Saving My Memory For When I Develop Alzheimer's" [/font]
[font color=blue]78 F-150 429CJ,Silver,Explorer Pkg.
641/2-Mustang 260,Pre-World's Fair Car.
64-Fairlane500 S/C waiting for a 390-4spd.
68-Mustang 289-Sunlit Gold 80,892Mi
78-Buick LeSabre 403 4V
84 Volvo DL Wagon [/font]
Junior User
Joined: Mar 2001
Posts: 79
Likes: 0
From: Granger, IA
alternator/charging, need help quick!!!!!
Brand new battery today and i have a battery tester just like the on i use at an auto parts store. As for a multimeter, i was using it earlier today and i had around 12.5 volts, but no amps whatsoever. I know a fair bit about electrical stuff, but this has me totally lost.
Posting Guru
Joined: Jun 1999
Posts: 2,415
Likes: 3
From: Comox Valley, Canada
alternator/charging, need help quick!!!!!
12.5 volts when? Engine on or off? How did you measure the amps?
It sounds like the system isnt charging properly. Since you replaced the alt and reg we can assume they are good, of course this isnt always true as many people here have learned....new doesnt always mean good
That said how about a slipping alt belt or possibly bad positive/negative battery wires, or bad wiring to from alt and/or reg?
Also make sure the reg and alternator cases are grounded, can make a big difference if they arent.
Quick charging system check:
a) truck off approx 12 volts at battery - means battery is charged
b) truck running 13.5 to 14.5 volts at battery - means charging system is working at no load
c) turn headlights on voltage should drop then recover to 13.5 to 14.5 - means regulator is working as it senses increased demand and compensates for it
d) engine at approx 1500rpm 13.5 to 14.5 at battery; turn on accessories one at a time, headlights, heater fan, wipers; voltage shouldnt drop below 13 volts - means alternator can handle the largest load usually demanded of it, ie driving at night in the rain with the heater on
Sparky
It sounds like the system isnt charging properly. Since you replaced the alt and reg we can assume they are good, of course this isnt always true as many people here have learned....new doesnt always mean good
That said how about a slipping alt belt or possibly bad positive/negative battery wires, or bad wiring to from alt and/or reg?
Also make sure the reg and alternator cases are grounded, can make a big difference if they arent.
Quick charging system check:
a) truck off approx 12 volts at battery - means battery is charged
b) truck running 13.5 to 14.5 volts at battery - means charging system is working at no load
c) turn headlights on voltage should drop then recover to 13.5 to 14.5 - means regulator is working as it senses increased demand and compensates for it
d) engine at approx 1500rpm 13.5 to 14.5 at battery; turn on accessories one at a time, headlights, heater fan, wipers; voltage shouldnt drop below 13 volts - means alternator can handle the largest load usually demanded of it, ie driving at night in the rain with the heater on
Sparky
Junior User
Joined: Mar 2001
Posts: 79
Likes: 0
From: Granger, IA
alternator/charging, need help quick!!!!!
Looks like from the posts that my fear has come true. All of the major/easy to replace parts are new and still in good condition. The wiring didn't match with the Chilton's diagram and it is obvious that the wiring has been modified before. I'll go ahead and rewire the whole alternator circuit in the engine bay, any specifics that a Chilton's diagram might leave out or some other little detail that'll come back and haunt me later? Just like to know before I go "fixing" the wiring.
New User
Joined: Jan 2008
Posts: 0
Likes: 24
alternator/charging, need help quick!!!!!
I don't whether this will help you.
Let's hope so.
https://www.ford-trucks.com/user_gallery/sizeimage.php?&photoid=1730&.jpg
Dennis https://www.ford-trucks.com/user_gallery/sizeimage.php?&photoid=1733&.jpg
[i][font color=red]Calgary,Alberta,Canada[/font][i]
https://www.ford-trucks.com/user_gallery/sizeimage.php?&photoid=3180&.jpg
http://community.webshots.com/user/mil1ion
[font color=green] Please Don't Ask Me Any Tough Questions,
"I'm Saving My Memory For When I Develop Alzheimer's" [/font]
[font color=blue]78 F-150 429CJ,Silver,Explorer Pkg.
641/2-Mustang 260,Pre-World's Fair Car.
64-Fairlane500 S/C waiting for a 390-4spd.
68-Mustang 289-Sunlit Gold 80,892Mi
78-Buick LeSabre 403 4V
84 Volvo DL Wagon [/font]
Let's hope so.
https://www.ford-trucks.com/user_gallery/sizeimage.php?&photoid=1730&.jpg
Dennis https://www.ford-trucks.com/user_gallery/sizeimage.php?&photoid=1733&.jpg
[i][font color=red]Calgary,Alberta,Canada[/font][i]
https://www.ford-trucks.com/user_gallery/sizeimage.php?&photoid=3180&.jpg
http://community.webshots.com/user/mil1ion
[font color=green] Please Don't Ask Me Any Tough Questions,
"I'm Saving My Memory For When I Develop Alzheimer's" [/font]
[font color=blue]78 F-150 429CJ,Silver,Explorer Pkg.
641/2-Mustang 260,Pre-World's Fair Car.
64-Fairlane500 S/C waiting for a 390-4spd.
68-Mustang 289-Sunlit Gold 80,892Mi
78-Buick LeSabre 403 4V
84 Volvo DL Wagon [/font]
Trending Topics
Senior User
Joined: Nov 2001
Posts: 121
Likes: 0
alternator/charging, need help quick!!!!!
I know zero about electrics but had that happened to me--alternator quiting while driving. I watched my mechanic friend check out the charging before installing the new alternator and he checked every inch of the circuit and every connnection, especially going into the regulator, because he said he has seen lots of fords show poor/no charge from frayed, corroded wires and you couldnt assume it was the alternator. He checked alternator output by going around the regulator and the connecting harnass just to be sure it wasnt the regulator, which is usually the first place to look on Fords. if this is any help
FTE Stories
Ford Trucks for Ford Truck Enthusiasts
3 Best / 3 Worst Parts of Modern Ford Ownership
Brett Foote
10 Amazing Upgrades That Solve Common Ford Truck Owner Headaches
Pouria Savadkouei
Every 2026 Ford Engine Explained
Brett Foote
10 Ugly Ford Trucks That We Still Kinda Love
Joe Kucinski
10 Things Every Truck Owner NEEDS (2026 Edition)
Michael S. Palmer
Rezvani's Latest Post-Apocalyptic Monster Is a Ford F-150 Raptor Underneath
Verdad Gallardo
Top 10 Most Expensive Ford Trucks Ever Sold on Bring a Trailer
Joe Kucinski
2027 Ford Super Duty Buyer's Guide (Every Model, Engine, & Package)
Brett Foote
Top 10 Ford Truck Tragedies
Joe Kucinski
Postmaster
Joined: Apr 2000
Posts: 2,838
Likes: 6
From: SD
alternator/charging, need help quick!!!!!
I think the regulators are grounded through the mounting bolts, if I'm not mistaken. Might want to be sure the regulator has a good clean connection where it mounts to the body.
Just a thought.
Marty
Just a thought.
Marty
Lead Driver
Joined: Nov 2000
Posts: 6,636
Likes: 349
From: Albuquerque
alternator/charging, need help quick!!!!!
I've seen problems with the connector to the regulator getting a little crusty or loose. Wiggle it around while the engine is running to see if it picks up. Also I've read you can ruin the alternator by connecting the regulator up with the battery connected.
Good Luck,
Bear Tracks
Good Luck,
Bear Tracks