Charging issues

[jdm_sixtwo]

Alright I’m really out of ideas at this point. Truck was getting a random battery light and the code it threw was system voltage low. Set my SCT to show system voltage so I could always see it, and when it would trigger it was 11-12 volts monitored and only when cruising, at idle it would be 12.5, which is still low. Went ahead and changed alt with a OEM ford alt, cleaned all corrosion from battery terminals and wire brushed them, and redid several body grounds. Immediately I had 14 volts and figured all was well, but realized as I drove voltage got lower and lower, until batt light eventually comes on again. Now at idle it’s only making 13.5 cold at 13 warm, and cruising I’ll still get a battery light after 30 minutes. Battery is less than a year old continental, and tested fine on my old tester. Any ideas here? Kinda at a loss.

 

[wheelman55]

Maybe test the alternator? Good luck!

 

[jdm_sixtwo]

Maybe test the alternator? Good luck!

Tested good

 

[mprice1234]

I would look further into the battery; how new the battery is doesn't mean it hasn't gone bad.

 

[jdm_sixtwo]

I would look further into the battery; how new the battery is doesn't mean it hasn't gone bad.

I’ll probably steal a battery from something else and see, I think my battery tester sucks

 

[Chewie]

Alright I’m really out of ideas at this point. Truck was getting a random battery light and the code it threw was system voltage low. Set my SCT to show system voltage so I could always see it, and when it would trigger it was 11-12 volts monitored and only when cruising, at idle it would be 12.5, which is still low. Went ahead and changed alt with a OEM ford alt, cleaned all corrosion from battery terminals and wire brushed them, and redid several body grounds. Immediately I had 14 volts and figured all was well, but realized as I drove voltage got lower and lower, until batt light eventually comes on again. Now at idle it’s only making 13.5 cold at 13 warm, and cruising I’ll still get a battery light after 30 minutes. Battery is less than a year old continental, and tested fine on my old tester. Any ideas here? Kinda at a loss.

Might be a long shot, but just dealt with a similar situation on another vehicle of mine. Follow the charge wire from the alternator to all of its junctions until you get back to the battery. Since your alternator is testing good, the problem is between it and battery.

Mine ended up being a failed crimp at the starter solenoid where the charge wire just pulled out of the O-ring lug terminal. Drove me nuts for days since it looked good until I pulled on the wire to see if it was burnt anywhere and it ended up in my hand.

 

[jdm_sixtwo]

I’ll check it later. Sorta limped the truck along and I still can’t figure it out. Sometimes it’ll just give up on charging altogether and there’s no magnetic field around the alt, the rest of the time it’s just sorta weak. Almost like the PCM just forgets to command it to charge sometimes. At cold starts sometimes I have 14.1 and sometimes I have 12.9. No rhyme or reason to it. Totally stumped, and really bad timing because I’m really trying to sell the truck.

 

[jdm_sixtwo]

I’ll check it later. Sorta limped the truck along and I still can’t figure it out. Sometimes it’ll just give up on charging altogether and there’s no magnetic field around the alt, the rest of the time it’s just sorta weak. Almost like the PCM just forgets to command it to charge sometimes. At cold starts sometimes I have 14.1 and sometimes I have 12.9. No rhyme or reason to it. Totally stumped, and really bad timing because I’m really trying to sell the truck.

Checked. All cables down there are good.

 

[neovenator]

Is the battery under the warranty period? I would replace it, or pick up the Everlast batteries from Walmart. Batteries can fail and be defective, but it's pretty rare, but still possible

 

[jdm_sixtwo]

Might as well. Should be under warranty still. I’m gonna get my ForScan back from my buddy and test commanded vs actual voltage, and you can cross the command wire with the feed wire and see if the wiring is all good so I’ll do that too once I have the scanner. That’ll at least rule out PCM which is near impossible to find for my truck.