starting a new thread on this .



last week I gor a "service charging system now" message followed by a battery light that stays on.

battery charge voltage was in the 13.9 to 14.6 range, initially in the high 13's after startup and stabilizing at high 14's a few minutes after starting.

pulled both batteries to test and found the pax side battery had corrosion on positive terminal and as a result of that was not getting a charge...was sitting at a 10V rest voltage.

the only ford dealership in the county only had a appt 4 months out for electrical problems (dealersip does not like warranty work and would rather do oil changes all day long)

bought 2 new batteries

replaced both batteries.... "service charging system now" message followed by a battery light that stays on continues

on the advise of forum members, used forscan to reset the BMS. "service charging system now" message followed by a battery light that stays on continues

upon replacing the battery , noticed with hand held scanner that has alternator test/monitor feature...the voltage will spike to 15.1 occasionally. using forscan or forscan lite, voltage appears to be reported as an average in the low to mid 14's.

alll along the batteries are charging fully.

did some googling and found cases of bad primary alternator being the culpprit for cases in which there is wide primary voltage fluctuation...since mine spikes to 15.1 im wondering if this is my problem?

also found videos that isolates the problem to bad wiring on the lower pax side of engine that breaks due to how ford straps the wire loon down...a few videos show how to by pass the wire with a jumper to verify its a broken wire in the loom. this could also be my problem since their is some intermittent fluctuation going on.

cant wait for July 6 to resolve this and will have no choice but to throw parts at it.

if wiring problems cant be isolated, my plan is to replace the primary alternator.

I have forscan but dont have any base line numbers that I should compare.

again the batteries are being charged so not on the side of the road yet.

if anyone has any been there done this recommendations, would certainly appreciate it.

once I put forscan on it..I was able to read the error code "generator control circuit error"

I was also thinking of making a pair of alternator PCM extension cables so I could flip the PCM connections on both alternators.....my thoughts are if the message and light stops....this would verify its an alternator problem since the secondary does not normally come on line until high loads and if the primary was weak it wouldnt manifest an error during a low load state if alternator PCM connection was swapped. if the problem remains after swapping the PCM connections....that would lead me to believe its in the wiring circut of the primary alternator .

anyone have any tests or checks I can do before I go down this path of making PCM extension cables to swap primary/secondary alternator roles?

thanks for any help provided.

also, I can get an appt at a dealership 2 states away (90 minute drive) for early march. will likely have to leave it and get a rental. this will cost me time and money anyway so not concerned about spending some money to fix myself if all I need is a new primary alternator.

I dont think replacing the batteries will hurt my warranty case...not sure if I replace the primary alternator if that will hurt my warranty case.

thanks again

 

Started truck up today and got 14.3 volts right after startup

batteries are obviously charging

error message and battery light continues.

puzzling

 

Speakerfritz
You may need to remove the alternators and have them tested. You can blow/burn a positive diode and still get 14+ volts out of a unit and charge the battery until you shut it down. Then alternator slowly drains the battery, a new battery takes longer to drain, better reserve the an old battery. Take them to a alternator rebuild place and have them bench tested under load, a hand held tester cannot tell you if a single diode is bad. The battery light is an indication the something is not right with the alternator

Good luck
Smokeploe

 

Thanks for the reply.

I’ll look around for a shop that can do that.

I did test for a bad diode and got zero ac volts.

 

There is a wiring harness that runs under the engine, I think towards the front. There have been a couple of posts on that harness grounding out and causing gremlins. It might be worth your time to crawl under the truck and poke around.

 

tes, I saw a few videos about that

 

I've watched a few videos with a similar problem you are having. Like others have stated it could be the bad charging wire next to the oil pan passenger side. It would be odd for this issue to arise at such a low mileage though.

From my understanding if there is a chaffed/corroded wire the resistance of that wire drops therefore the alternator increases voltage then the PCM picks up the high voltage and throws the battery light.

 

Jump to the 2 minute mark. The Tech also mentions he has never replaced an alternator on a 6.7 it's always the wiring.

Here is the other location Jump to 6:45

 

In digging in to the wire looms today.

so far they look and test fine.

took it for a 30 minute ride and charge voltage is 14.25

no ac volts

will keep at it.

thanks everyone

 

You never mentioned what code you have?

 

Plus 10 characters

 

Plus 10 characters

 

Ode is a p0620

generator control circuit

it the spooky thing is I have a consistent +14.3 charge voltage at the batteries


Red wire on pax side alternator pcm connector matches charge voltage

no ac volts at all

 

Since it's a DC system, I wouldn't expect AC volts.

 

So my understanding is if there is a shorted diode, ac will show up at the battery posts indicating an alternator problem.

I tested for ac volts and got zero.