Battery Light on

Eric Technician Illinois Posted   Latest   Edited  
Updated
Electrical
2015 Ford F-250 Super Duty XL 6.2L (6) 6-spd (6R140) — 1FTBF2A66FEC64860
P0625 — Generator Field/F Terminal Circuit Low
Battery Light On But System Charging

Ok this truck came in with the battery light illuminated but the system is charging at around 14.1 according to the voltage pid. New alternator installed and has this issue. I have verified and load tested with a 9006 bulb the battery cable at the alternator as well as circuit sdc14 red wire. Not sure as to what I should see on the Genmon and Gencom wires, I did scope them but do not have a reference to know if they are good bad or ugly. Or if I am just chasing my tail, currently I only have generic obd capabilities as our autel is dead and awaiting repairs.

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Interesting
Caleb Diagnostician
Indiana
Caleb
   

So the old alternator was charging but the battery light was on? Have you verified both wires are good from alternator to ECM??

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Eric Technician
Illinois
Eric
 

Both wires showed .5 ohm between the alternator and ecm. Yes same complaint with the original and this aftermarket replacement. I have run into the previous gen fords that had the ipc that kept the light on. But nothing on one this new.

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Glenn Owner/Technician
Texas
Glenn
 

Hi Eric, I recommend a new Motorcraft alternator. These systems are very picky about the regulators. Aftermarket is junk.

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Dan Owner/Technician
Texas
Dan
 

… I agree with Glenn. … Dan H. … Hobbs … South Texas …

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George Owner/Technician
Alabama
George
   

I don't agree…..Lets try a new motorcraft before we test the system…Sounds crazy Could be that's why rebuilt aftermarket has a bad name…..If it don't work put a OE on it…Turn in the 2…3…4. aftermarket that may still be good….

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Dan Owner/Technician
Texas
Dan
 

… I agreed with what Glenn said… and then you said you don't agree …but … then you said the same thing he did …put a Motorcraft on it … you lost me there with your reason that you don't agree with what he said… I'm confused with your disagreement… Dan H.

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Robert Technician
Michigan
Robert
   

I agree with a few quick tests on this system but probable is the regulator or is it ..Cant tell whats going on here from what is written ,Scanner says 14.1 v and scope says 10.2 and Ford default is 13.5 at I forget 2500 rpm regulator unplugged ….. p0625 and p0626 are the easy codes to check

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Eric Technician
Illinois
Eric
 

Sorry I didnt label the scope pictures very well. The left picture is the Genmon signal and the right it the Gencom signal.

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George Owner/Technician
Alabama
George
   

Dan…. That was a quote from what many say on many posts after several replacements…Sry for the confusion…I am sure Glenn meant use OE 1st

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Glenn Owner/Technician
Texas
Glenn
 

No worries George, When you quote something use “ quotation (double) marks" if it is someone else has said it before. If it is an original quote from you use ‘single’ marks. Using periods like…. means you are pausing briefly while writing, then you continue your thought. I am not an English major, but the English language is actually one of the most difficult on earth, so it is hard for many…

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Dan Owner/Technician
Texas
Dan
 

… Glenn … I reckon that means that I think a lot…lol… Dan H. … Hobbs … South Texas …

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Glenn Owner/Technician
Texas
Glenn
 

Dan, I know the feeling.

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Glenn Owner/Technician
Texas
Glenn
 

Hi Dan, His punctuation made his reply a bit confusing, but he disagrees. I'm not rattled much by others opinions. The Twilight Zone strikes again? LOL These ‘smart alternators’ are a crap shoot, especially on Fords. Often times OE is the only solution. (We've both seen it happen too many times). He (George L.) apparently puts a lot of faith in aftermarket electrical component. I disagree…

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George Owner/Technician
Alabama
George
 

Most of the time I have more faith in the rebuilt vs the person doing the testing.

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Kyle Mechanic
Illinois
Kyle
 

GENERALLY speaking on Fords you can short GENMON and GENCOM together with a paper clip with engine off. Start truck up while monitoring with a scanner and the waveforms should mirror each other for I think about 10-15 seconds or so until it trips a fault. If they mirror each other then you have confirmed your GENMON, GENCOM and PCM are all working as designed and your alternator would be at…

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Eric Technician
Illinois
Eric
 

Thanks for the information. I will give it a try if I get a chance to get back on it. My boss likes to punt jobs that he deems to difficult.

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Glenn Owner/Technician
Texas
Glenn
 

Hi Eric, I am sorry to hear that, but I also understand your boss is likely profit driven. He wants quick turn jobs with high profit margins. He does not realize he's cutting his own profits because he is avoiding being the “Go to Shop”. This may also depend on the customer base as well, some customers expect miracles and have no concept of diagnostics. It is likely the owner does know how to…

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Juan Owner/Technician
Georgia
Juan
 

same issue happened to us at our repair shop on a 2012 explorer, vehicle came in with a no charging complaint, it was verified . we replaced it with two AZ alternators and both had the same simptom as you do. we tested related wiring, did the battery reset and all pointed to the alternator. So we ordered a new motorcraft alternator and all was good.!

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Robert Technician
Michigan
Robert
 

Just throwing it out since I took a look .

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David Owner/Technician
Minnesota
David
 

I have seen wiring for the alternator get damaged in the plastic tray under the front of the oil pan, from what i remember they aren't in a loom running through it. I believe it is somewhat of a common area for the alternator wiring to get damaged on the superdutys at least with the diesel,not sure if it applies to the gas models. They will still charge with the wiring damaged but the computer…

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Glenn Owner/Technician
Texas
Glenn
 

Hi David, It is good you brought that up, these alternators have a default charging program and will charge without command or in the event of disrupted command from the ECM. It is part of Ford's strategy and usually the alternator will charge by default when the engine is accelerated as long as the brushes are good. In other words, alternator command plug can be disconnected and it will still…

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Paul Mechanic
Illinois
Paul
   

Ford's tend to default to a fixed charging voltage when PCM cannot gain control. Usually codes within 10 seconds after code clear and restart. You'll see it on the gen pids trying to control then just flat line. AZ remans have caused me nothing but trouble on Ford smart charging systems. Longest one went was 6 months, then the two replacements were both charging at 18 volts back to back. It's…

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Eric Technician
Illinois
Eric Update
 

Well as I figured the truck was shipped this afternoon, so I will probably never hear what the issue is. Thanks for all the responses it is greatly appreciated.

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