I have a 2013 F150 XL 3.7L with 139,00 miles. Since it still had the original alternator (which was working fine) I decided to change it anyway. I've been working in alternator/starter rebuild shops for 47 years and this has me puzzled. I bought a core from a junk yard so I could rebuild it ahead of time and swap it out in one day. The only regulator that's available are aftermarket ones. Even my Denso distributor doesn't sell it in OEM. I used an aftermarket regulator from a company that from past experience provides a good quality product. Did a total rebuild , bearing, brush holder, slip ring, rectifier and regulator. Put the new alternator on and now the voltage fluctuates between 13.5v to 14.4v ( I have a digital gauge in the dash ) and the battery light will occasionally flash and chime then go back out. Let the truck sit overnight hoping the BMS would reset but same problem this morning. Also disconnected the current sensor on the negative cable and made no difference. The alternator that I took off was working fine so I guess my next step is to put new bearings and brushes in it, reuse the OEM regulator and put it on to see if it makes a difference.

 

i assumed it was the "management system" that was doing all the work......... but you might be right on the REGULATOR being part of the problem.

 

I also want to add that I didn't have the battery disconnected. Since the output cable at the alternator has a big plastic insulator on it I just moved it out of the way when I took it off. If nobody comes up with a solution I'll post the outcome after I put the original alternator back on. You would think that if it's the regulator, everyone who buys a reman alternator from a parts store would have the same problem. I have had customers who claim that only an OEM alternator from the dealer would work on certain applications.

 

The alternators for these trucks do seem to be proprietary as far as working right, something about the smart regulator in them that after market hasn't figured out yet. The alts will charge but you're left with a glowing battery light. Common complaint over many forums.

 

I'm pretty much convinced the regulator is the problem since I wasn't having trouble before. The test bench we have at work is capable of checking PCM controlled alternators. I checked the junk yard core before rebuilding it and it didn't work. Nothing checked bad when the unit was disassembled so I had no choice but to use an aftermarket regulator. I'm off on Monday but I'm going to go in and freshen up my original one and put it back on. We'll see how that works out. P.S. I also checked the regulator plug. Cleaned it with contact cleaner and it was fully plugged in. At least it's easy to change. I also changed all the belts and tensioner while I was at it. The A/C stretch to fit belt was the worst part to change.

 

Changed the bearings and brushes on my original alternator and re used the OEM Denso regulator. Truck charges fine now. I'm waiting for a call from tech support for the aftermarket regulator that gave me trouble to see if they know of an issue. I'm also going to order another brand of regulator from another supplier and try it in the rebuilt alternator. Since it's so easy to change I'll go through the trouble of doing it to find out what does or doesn't work. That will help in the future if a customer has the same complaint. I'll post an update at a later date.

 

Good move and thumbs up on your effort understanding whats going on, for your sake as a repair shop, and for customer satisfaction.

 

Got around to installing a different manufacturers regulator in the rebuilt alternator, installed it and it works fine. It was so much easier to diagnose charging problems before they went to computer controlled systems. Only because I took off a working alternator did I suspect a problem with the rebuilt one when I put it on. The rebuilt one checked good on our test bench. I have to confess that there have been times when a customer returns a rebuilt alternator and it tests fine that we tell them they must have another problem. In all fairness I have to say that this particular regulator fits many different Ford applications and it may not be a problem on another vehicle. There's also a possibility that I simply had a defective regulator the first time but I doubt it since it was charging. The only problem was it made the BMS go out of wack. I've also had customers return rebuilt Ford alternators repeatedly that checked good. In those cases we usually give them a different unit to rule out the problem but they claim the only solution was to use an OEM Ford alternator. I was lucky because I started this only as preventative maintenance because of the milage on the truck. I knew I had a working alternator and having installed a digital voltmeter in the dash helped me to see what the charging voltage was. I purchased the core for $40 and put another $40 in parts and figured I'd save the original as a spare. What happens to the poor guy who really has an alternator fail, goes to the parts store and buys an exchange and still has a problem? When that one doesn't work he starts chasing a ghost that doesn't exist. I'm not saying that all rebuilt parts don't work ( the majority do ). All I'm saying is just because you replaced a part and it doesn't work don't start looking for another problem right away. Start trouble shooting the problem as you would have before.

 

Ford's better idea to maintain alternator sales well into the future? It's crazy I know but I've seen time and time and time again over and over ad nauseum. Something proprietary about that smart circuitry that eludes after market builders. Every single complaint I've come across was the battery light either staying on or flickering at times and every single time tested the alt was indeed charging per spec. Put an oem Ford alt on there and problem solved.

If I were to dig into the why, 1st thing I'd do is connect an o-scope and see what kind of waveform was emitting from a known good unit then compare it to one known malfunctioning. I'd be willing to bet $$$ there's some little glitch in the waveform that they programmed the IPC and/or BCM to monitor and gave it a very slim margin +/- and if it's not in that margin, BAMM battery light on.

Or perhaps there's a timed voltage jump/drop designed in for the IPC and/or BCM to monitor for such as a 3.14v dip in voltage every 50 revolutions or ahhhhhhh who knows, man Ford does some weird schit on the drawing board.

 

One outcome is that we are no longer going to use the regulator from the supplier that gave me the problem. I know that the second one works and will continue to use them.

 

Everything was working fine until I changed the battery. Got a good deal on a brand new battery and since mine was 3 years old I decided to replace it. As I mentioned before, I installed a digital voltmeter in place of the coin holder to better monitor the charging system. The original alternator problem was resolved as posted before and charging voltage was always steady. Put in the new battery and let the truck sit overnight like others have suggested. Coming home from work the next day I noticed the voltage would fluctuate from 14v down to 12.7 then after a few minutes would go back up. No warning lights like I had with the regulator problem. I disconnected the battery sensor coil on the negative battery cable after reading other posts. Charging voltage is steady now at 14v and no repeat of the problem since.

 

I had my OE 2013 battery replaced at my local Ford dealer thinking I'd have no troubles after. Boy was I wrong! Unplugging the BMS solved my issues.

 

The battery died in my 2013 F150 XL 5.0L a couple of months ago. It had a 3 year old 750 CCA, and I replaced it with an 850 CCA from O'Reillys. No problems, no warning lights and the BMS is still hooked up.

 

If it weren't for the digital voltmeter that I installed in the dash I would never have noticed any difference. No warning lights, just fluctuating voltage.

 

But is that fluctuating voltage an actual problem? If the battery stays charged, and doesn't overcharge, what problem would there be?

A few years back, I owned a new 2013 Silverado and the alternator would turn off while you were driving. On purpose, supposedly to save one one-thousandth of a percent on the gas mileage.