ive been searching the internet trying to figure out what the issue is with my truck (2018 3.0 powerstroke f150 lariet) and have found only one response to an electrical issue like mine. i got a "check charging system system" warning from my truck. its 5 years old so i assumed the battery was on its last leg. makes sense. i replaced the battery. new battery did not fix the issue. i drove is for a few hours hoping the codes would clear once the truck recognized the issue was resolved. it was not. i dropped it off at the dealership because i was leaving the country and i did not have time to work on it myself. dealership said "they think" it the alternator. the alternator was going to cost $1500!! and after diagnostics and installations it was going to cost me over $2200 for a new alternator. my motorcraft A/C went out at 65k miles and now my motorcraft alternator went out at 75k miles so i was about to be grossly overcharged for another garbage motocraft part with no warranty. so after much head ache i got the truck home and installed a duracraft with a lifetime warranty for $400.

ok, so heres the thing. the motorcraft alternator was consistently putting out overvoltage (up too 17.8 volts) it would go back to normal from time to time. the new duracraft alternator puts out maintained a consistent 14.3v but then shortly after install started the same behavior, putting out over votage over 17 volts again. i have forscan and there are multiple codes being thrown. Mass airflow senor "high voltage", air temperature sensor "low voltage" and glow plug "high voltage". several other codes are thrown here and there but after reset these 3 are the ones that always return.

the only response i have found to an issue like mine was that in newer vehicles the internal resistor in the alternator has been replaced by a computer monitoring system. but no solution was given.

i replaced the mass air flow sensor, (that what i could find same day) no change. given the situation and the temp sensor reading "low voltage" could the truck be upping the voltage to compensate for the temp sensor and applying over voltage to the rest of the system because of this??

any knowledge, expertise and advise greatly appreciated.

thank you

 

I'm not an expert. Newer alternators are controlled by the PCM.(a pulse width modulated signal that sets the output voltage) Something is causing the PCM to send the wrong control signal. Use Forscan to monitor all PIDs associated with voltage and charging. You may have to put a scope on the alternator control signal to see what's going on. The stupid dealership should have done this.

It may be as simple as the PCM getting bad voltage info due to a loose connection.But the fact that the Duralast alternator is also misbehaving points to something outside the alternator.

 

I appreciate the reply i tried watching any pids i could think might be relevant, I didn't see any helpful info. so here's the update. i put the motorcraft alternator back in, the codes were the same. so while trouble shooting i disconnected the wire going back to the air bags on my truck. the fuse wasn't blown but it was ringing out when i ohmed it to the frame. that cleared all the codes except these 2 codes

P065B:007-C - Generator 'A' control range/performance
and
P0625:007 - Generator field/F terminal circuit low

ok... so i figured maybe the old alternator was actually bad and i put the new duracraft alternator back in the truck. (as you can imagine im pretty damn good at replacing an alternator in a 3.0 powerstroke now) but the codes remain...

now... heres the wild thing. no overvoltage, except one time when i closed the hood of the truck. the truck started doing all the crazy stuff again and pumping out over voltage, i pulled the hood release... and it all stopped. yet to return. the "check charging system" and battery light are still there due to the codes but that hood insodent is the only time the overvoltage returned. ive been trying to trouble shoot the problem. my next step is to disconnect the hood latch sensor? kinda just stabbing at thin air at this point.

do you think that dead short could have killed the original alternator and then the new one possibly as well? as far as i can tell this is a communication error between the PCM and the alternator.

again any advice is appreciated

 

Since I have never troubleshot these types of alternators, I am little help. But I definitely would start with wiring diagrams. The hood slam incident points toward a wire rubbing against something and causing problems.

Hopefully others with firsthand experience will join the discussion.

 

The service manual for my 2016 Transit Connect explains the smart charging system. It's complicated. It involves the ABS module to determine vehicle speed.....who knew? I don't know if your truck uses the same system. It it does you will need more information to troubleshoot your alternator problem.

 

ok so i fixed it. all that head ache for a tiny little wire. long story short the communication wire going from the alternator to the PCM was broken. so i spliced in a new piece of wire and rerouted it.

i took alternator back out once again. i traced the communication wire from the alternator to the PCM. they were bunched in with a bunch of other wires in a main run. the run ran under the engine and through channels that were impossible to get too so i assumed the break had to be under there because that would be the hardest to fix so thats where it would be of course. i used an ohm meter to check the connection between the ALT connector and the PCM connector. there are 3 wire on the ALT connector so i tested all the wire ports on the PCM connector until i found all 3 wires. i got .5 ohms on 2 of them and .08M ohms on one of them. so thats the one that the problem. i traced the run to a point i could easily take the protective covering off and and find the correlating wire (in this case the red/white wire) then i cut the wire there and at the ALT connector. ohmed out from each cut spot back to the correlating connector to be sure the break was where i assumed it would be, then spliced in new wire and rerouted it. that wire now reads .3 ohms from connector to connector and all codes are cleared, no more overvoltage.

the dealership would have charged well over $3000 for a 10 cent fix so it was worth the effort.

thanks for your replies and trying to help.

hope this is helpful to someone else in the future.

 

EVEN MORE HELP FOR THOSE WITH OPTIONAL 2ND ALTERNATOR.

Battery Voltage Spike... | Ford Powerstroke Diesel Forum

QUOTE; Check your wire connections and continuity for a corroded or broken connection. A VOM will suffice. Alt. 1 to Alt.2 ..... Alternator / starter repair business do well with these things.
Check for a great repair shop near you. Driving at 17 volts will start blowing stuff, beginning with Bulbs and lights.


After replacing both alternators and batteries due to voltage spiking, because everything pointed to one of those options...I wasted about $1500 on unnecessary items..... If you have voltage spiking consistently then your alternator is working but not being regulated.... On my 2018 6.7 Diesel, i have 2 alternators, the plug on them has three pins, if you do not have the same voltage as the battery, or if the line sensing pin reads zero, then there is a break in the line somewhere. I pulled the plug out of the main alternator and my voltage went from 16 volts to 13.6 - 13.8 v, but if you run it this way the smaller amp alternator will overheat. When i plugged back in the drivers side bigger amp alternator i started getting spiking right away..

→→→→....common sense would say the internal regulator was bad....not true, it was that the line sensing wire was not telling the alternator the correct voltage or saying it had zero, demanding full production out of the main alternator. ▬ ↑↓↔

I jumped a wire from the line sensing wire on the passenger side, smaller alternator over to the drivers side alternator line sensing wire and guess what....it now is a stable output without replacing the whole harness or paying $2,000 to have Ford put a new harness in.... You could probably run a fused wire right to the alternator from the closest battery to get the same result....mind you I am not a ford mechanic although an NCCER mechanic with experience industrially, but for some reason the parts changers at the dealership in my town are clueless unless a scan tool holds their hand through the repair process.
What pisses me off is i see a ton of people having this problem and Ford acts like they have never heard of such a thing, but they have plenty of harnesses available for sale??? I have only 75k miles on my truck and already the transmission had issues at 58k miles which my local dealership said they couldn't find an issue with it....so 1 transmission rebuild 2 alternators and 2 batteries out of pocket because warranty only went until 60k miles, i have a truck that although the motor is amazing, i would never buy again. Thanks Ford for your phenomenal dealership service. 🖕

Dual Alternators???? | Ford Powerstroke Diesel Forum .....

I could guess dual alternators come in handy with extra lighting on the Tow Vehicle at night or day needs. Maybe even AC power? I used to work on Industrial floor scrubbers with twin Alternators, one regulated for 14 volts, the 2nd one unregulated for 36 volts AC. It ran the twin 36-volt Vacuum turbines to suck up the sludge. A Delco 14 v. with diodes and internal voltage regulator and a Motorola 36 volt. full wave unrectified. 1 amp per volt basically under load 32.
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I have high in gen 2 line and control module voltage 63 I have f750 took alt tested good but reading frequency and the alt shop can't test that he said there is wire that goes bad I also bought ford manual anything after 2000 rpm it's supposed to auto 13.5 volts there 9000 plus pages in book it's not best trying to read it all from phone I was trying to print it but to much data or not doing something I did read it's pcm controlled I can look at book I think it said pin one and 2 with fused jumper and scan than said test ohms to case and pin and trace the wires out I have the info on it but digging it may be different but it's probably a bad wire from what the last guy that was at alt shop he had similar issues I did see video of one coming up to engine the wires rub through or break

 

did you guys figure it out i got frequency 16 should be .9 or lower generator issue 63 .47 volt in pcm dash read 14.3 effect turbo reading pegged egt fuel psi i belive the voltage is causing phantom reading this does it with alt disconnect not sure how long would take reset unhooked and tests ok but he cant check frequency im leaning towards a wire issue or pcm or alt i just havent figured it out yet dealer said alt alt shop said he had one like it was out trick or treating the guy had found bad wire i have manual but really not a lot help to many pages lol f 750 2019

 

I sent my ecu out just to see if something was wrong with it they said it's software so idk it could be a bad wire i sent it off before knee surgery it's back just haven't put back in I would think if it's wire should be able to figure out we did have it reading beep on ohms just see if contact I also was reading could be from ficm but that seems for older than 19 may have injector causing or any thing that is giving power 63.47 volts I forget codes but heading to shop tmrw

 

Did you note what pins or wire colors I'm still trying to figure mine out I started with turbo full over boost reading then egts temps fuel rail psi started showing up thats about when I seen 63.47 volts I did see gen feild circuit high