Alt charging woes
Thread Starter
|
New User
Joined: Jan 2012
Posts: 10
Likes: 0
Alt charging woes
I have a 77 f250 I just bought recently and everything seemed good but the old alternator wasn't charging (or so I thought). Truck would run until the battery died, I watched the gauge go from 9 volts and run down to 3 volts and the truck dies.
So I did a 3G swap today, following the diagrams on here, and the same thing happens...
Am I missing something?
So I did a 3G swap today, following the diagrams on here, and the same thing happens...
Am I missing something?
Posting Guru
Joined: Feb 2013
Posts: 1,323
Likes: 3
From: Sunny Florida
When you say 3G, what do you mean? I am assuming you are talking about what us car audio enthusiast call the big 3... alternator to positive, negative to frame, and block to frame. If so, what gauge wire did you use? If you did not do it, I would start there. Next would be the battery and alternator.
Thread Starter
|
New User
Joined: Jan 2012
Posts: 10
Likes: 0
When you say 3G, what do you mean? I am assuming you are talking about what us car audio enthusiast call the big 3... alternator to positive, negative to frame, and block to frame. If so, what gauge wire did you use? If you did not do it, I would start there. Next would be the battery and alternator.
Swap to the 3G 130 amp alt, used the wire that was attached to the alt.
It'll run with a little juice in the battery until that runs out.. It's a reman alt so I didn't have it tested, guess I should but as the pic shows it was rebuild/made 7/2012.. But does the same thing with the old alt on.. Just wondering if I missed something
Certified Thread Hijacker
Joined: Aug 2001
Posts: 14,441
Likes: 60
Yellow wire circles back and attaches at the cable lug on the back of the alternator.
Green/Red ties into the existing green/red or wired into a KEY-ON positive voltage source.
Without the green/red connected the alternator will not excite and begin charging.
If you did connect to the old green/red verify you have 12 volts with key-on. If not, trouble shoot the issue or use an alternate key-on source.
Josh
Certified Thread Hijacker
Joined: Aug 2001
Posts: 14,441
Likes: 60
When you say 3G, what do you mean? I am assuming you are talking about what us car audio enthusiast call the big 3... alternator to positive, negative to frame, and block to frame. If so, what gauge wire did you use? If you did not do it, I would start there. Next would be the battery and alternator.
1G: early 60s to 80
2G: early 80s to early 90s
3G: early 90s to early 00's
4G: Late 90s to current
6G: Late 90s to current
By far my favorite is the 3G. The 2G got a bad rap due to the alternator charging cable routing, but is actually similar to the 3G with lower amps.
4G is a goofball.
6G, is decent in theory, but a major dud, especially with diesels. I replaced the 6G in my 2006 Superduty with a 3G.
1G is adequate for old lighting, points etc. Once the headlights are upgraded, aftermarket stereo, electronic ignition, electric fans etc are added it cannot handle anything.
Josh
MSEE
Joined: Apr 2004
Posts: 10,386
Likes: 35
From: Austin, TX
I was going to make the exact same recommendation as Josh did. This is why it pays to understand why your original charging system was not working before performing any sort of upgrade.
Trending Topics
Posting Guru
Joined: Feb 2013
Posts: 1,323
Likes: 3
From: Sunny Florida
"G" refers to the generation of the Ford alternator and has nothing to do with cables.
1G: early 60s to 80
2G: early 80s to early 90s
3G: early 90s to early 00's
4G: Late 90s to current
6G: Late 90s to current
By far my favorite is the 3G. The 2G got a bad rap due to the alternator charging cable routing, but is actually similar to the 3G with lower amps.j
4G is a goofball.
6G, is decent in theory, but a major dud, especially with diesels. I replaced the 6G in my 2006 Superduty with a 3G.
1G is adequate for old lighting, points etc. Once the headlights are upgraded, aftermarket stereo, electronic ignition, electric fans etc are added it cannot handle anything.
Josh
1G: early 60s to 80
2G: early 80s to early 90s
3G: early 90s to early 00's
4G: Late 90s to current
6G: Late 90s to current
By far my favorite is the 3G. The 2G got a bad rap due to the alternator charging cable routing, but is actually similar to the 3G with lower amps.j
4G is a goofball.
6G, is decent in theory, but a major dud, especially with diesels. I replaced the 6G in my 2006 Superduty with a 3G.
1G is adequate for old lighting, points etc. Once the headlights are upgraded, aftermarket stereo, electronic ignition, electric fans etc are added it cannot handle anything.
Josh
Thanks for the info. I still recommend improving the you power and ground cables to at least 0 gauge for improved current flow. To give an example of what I am talking about, my Mustang is currently running a pair of Soundstream Human Reign amps that have a potential current draw of 360 amps. When listened to at moderate volumes I was experiencing major lights dimming. Improving the big three helped with this issue (did not solve it, a bigger alternator is needed for that much current) that existed even with the factory Mach audio.
FTE Stories
Ford Trucks for Ford Truck Enthusiasts
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
AEV FXL Super Duty - the Super Duty Raptor Ford Doesn't Make
Brett Foote
Lobo Vs Lobo: Proof the F-150 Lobo Should Be Even Lower!
Michael S. Palmer
Ford's 2001 Explorer Sportsman Concept Looks For a New Home
Verdad Gallardo
10 Best Ford Truck Engines We Miss the Most!
Joe Kucinski
2026 Shelby F-150 Off-Road: Better Than a Raptor R?
Brett Foote
2027 Super Duty Carhartt Package First Look: 12 Things You NEED to Know!
Michael S. Palmer
Posting Guru
Joined: Feb 2013
Posts: 1,323
Likes: 3
From: Sunny Florida
You have to think of it like this. The factory wiring in your truck has to run the interior and exterior lighting, the audio system, all accessories and wipers. If properly cabled, a reasonable amp (500 watts) requires 4 ga. power and ground wire. The factory wiring from your alternator to the battery is approx. 8 ga.. This basically creates a bottle necking effect when your electical system is trying to pull more current then your alternator can supply to the battery. Upgrading your alt to battery, battery to frame, amd block to frame cables allows your alt to do its job.
Thread Starter
|
New User
Joined: Jan 2012
Posts: 10
Likes: 0
Big cable to the Battery + or tied into the POS cable at the starter solenoid.
Yellow wire circles back and attaches at the cable lug on the back of the alternator.
Green/Red ties into the existing green/red or wired into a KEY-ON positive voltage source.
Without the green/red connected the alternator will not excite and begin charging.
If you did connect to the old green/red verify you have 12 volts with key-on. If not, trouble shoot the issue or use an alternate key-on source.
Josh
Yellow wire circles back and attaches at the cable lug on the back of the alternator.
Green/Red ties into the existing green/red or wired into a KEY-ON positive voltage source.
Without the green/red connected the alternator will not excite and begin charging.
If you did connect to the old green/red verify you have 12 volts with key-on. If not, trouble shoot the issue or use an alternate key-on source.
Josh
MSEE
Joined: Apr 2004
Posts: 10,386
Likes: 35
From: Austin, TX
Two big no-no's about this post:
Never load the 'I' terminal of the solenoid. With the key in RUN, this will change the voltage divider at the coil, and back-feed current through the ballast resistor.
Never run an engine with the battery disconnected. The battery acts as a current sink and provides some level of filtering for the alternator output; running the alternator without the load of the battery can let the output climb high enough to burn up any onboard electronics, including the ignition module. In some cases it can even burn out bulbs. The fact that the truck dies with the battery disconnected tells you nothing about the alternator; I don't know how that got to be such a heavily-circulated idea.
While it's still possible that you had two bad alternators, you still need to verify power coming out of the GREEN with RED stripe wire with the key in RUN. The 'I' terminal of the solenoid is not a 12-volt hot-in-RUN source. It's the start bypass circuit for the ignition coil. In RUN, you happen to see the voltage divider at the coil here. As I mentioned before, it's not meant to source current with the key in RUN.
While it's still possible that you had two bad alternators, you still need to verify power coming out of the GREEN with RED stripe wire with the key in RUN. The 'I' terminal of the solenoid is not a 12-volt hot-in-RUN source. It's the start bypass circuit for the ignition coil. In RUN, you happen to see the voltage divider at the coil here. As I mentioned before, it's not meant to source current with the key in RUN.
Certified Thread Hijacker
Joined: Aug 2001
Posts: 14,441
Likes: 60
Remove the positive battery cable and there is no longer any voltage on the green/red wire. And guess what, the alternator stops charging.
BTW, never do that trick. We drive Fords, not Chevy's
Josh
Thread
Thread Starter
Forum
Replies
Last Post
Sarco3
Pre-Power Stroke Diesel (7.3L IDI & 6.9L)
9
Mar 26, 2015 09:03 PM
elkarcher1716
1973 - 1979 F-100 & Larger F-Series Trucks
48
Apr 29, 2014 09:03 AM
Milwaukee1979F150
1999 - 2003 7.3L Power Stroke Diesel
26
Feb 9, 2012 01:13 AM