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Discussion Starter #1 (Edited)
Torque app reading low battery at 13.1v to 13.4v while driving, used to get 13.7v at idle. Alternator is within 4 years new, batteries are 1 year new. Seems like i have a grounding issue by my readings but trying to narrow it down. Below are the steps i've taken that leads me to believe i at least have an issue on the drivers side. I thought i had read threads and had a straight line testing procedure... but now i'm not so sure.

I started up the truck, waited a few min to let glow plugs go out... and i used my meter to check a few things.

Volt checks while running: (after cleaning posts and cable ends at battery, cleaning alt + post/end) (with car off both batteries are 12.7 before testing)
-Torque app reading is 13.1v to 13.2v.
-Back of alternator to ground of pass battery: 13.69v <--- Means alternator output is correct.
-------Here is where the head scratching starts and the... i thought i had a plan thought begins. Then the... f-it... lets just clean ALL the grounds!!!)-------
-Passenger battery reading between both posts: 13.61v <---- Ground to battery should be checked? (****, should of checked to another ground to verify voltage input?)
-Positive of pass battery to alternator case: 13.62v <--- this leads me to believe the input of for the battery is low? Since altern positive to ground post of driver battery was 13.69v. Or middle device does not have a good ground?
-Driver battery reading between both posts:13.57 <---Battery input is not where it should be. Need to search threads on connectivity between them? Or middle device does not have a good ground?
-Positive of driver battery to alternator case:13.58 <--- this leads me to believe the input of for the battery is low? Since altern + to ground post of battery was 13.69v

Any thoughts would be appreciated, i could just go and clean ALL the grounds on the frame and block. I just thought i could "test" to the problem. Found this setup on a different thread, Adding it for reference...(deleted as it was a "want to do" drawing). Found another, if i'm reading this right... it can be bad grounds at the pass and/or driver battery. Since the problem goes downhill from the alt, + of alt ---> pass battery ---> drivers batt. Right?

767938
 

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I would measure voltage drop on the grounds -- pretty easy todo
key off, and use the starter jumper wire on the RH fender

Measure from the engine block or the alternator case -- from each negative post(actual), while cranking
only need to turn a couple of revolutions
You are measuring voltage loss in the cable and connections, so you should see less than 0.5 volts on the meter
anything more and there is resistance in a connection

You can test the positive the same way, but need to connect the meter at the starter post

The battery system is connected in parallel, so each battery shares the load -- but the RH battery is connected directly to the starter, so it will take a little more hit
the LH battery is the supply for the computers and a supplement to the starting circuit

The alternator is connected to the RH battery and the LH battery gets charge from the cross over cable
there is a fusable link in the alternator wire that can give trouble sometimes
you can measure the drop on that one by connecting at the alternator output post and the RH battery B+ post
 

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Discussion Starter #3 (Edited)
Edit... I had a drop (didnt record the number, so im not going to memory make one up) from the + of the alternator to + of pass battery. I took apart the ground at the bottom of the block and cleaned it up. Now from the same link i drop ".07v". Now from the + of the alternator to + of drivers battery i get a total drop of .12v. Since the first jump is .07v and combined i'm at .12v the second segment has a loss of .05. Of course i didnt verify and go + batt to + batt... that would of been logical but whatever its not where the issue lies. .12v is not bad. Torque app shows 13.1v to 13.4 fluctuating. I've read up on all ground locations from video below, so i'm going to clean those as well. interested in ground connections G100 and G101 for sure.

1/2 of this is also in case anyone else has this problem.

Found this to help wrap my head around what you asked:

 

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Discussion Starter #4
Ok, update...with one question. Both batteries and alternator run at 13.8v after start+90 seconds, steady. FICM reads 48v and 13.v (which this whole time have been minimum 12.5). But my PID for battery voltage still jumps from 13.2 to 13.6 volts at idle. Every 1 or 2 seconds it will go in between 13.2 to 13.4... 13.2.. 13.6... I've cleaned all the ground connections and positive at alternator and batteries, there is .05v loss from the + of the alternator to drivers battery + which is good as i understand it. My only next step as a "test" is to see if the volts jump during key on engine off, maybe something is vibrating.

Two of the many grounds i cleaned were G100 and G101, which included FICM/PCM ground to body. As a test i did run a spare ground cable from both G100 and G101 to the battery ground, but it did not help stabilize the PID voltage. Is there a schematic or picture of where to check the other end of these connections? I feel i need to find the other end of the connection to verify. I cant seem to find it.

Thanks in advance for any assistance....
 

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I’ll try to type fast.

OBD reports up to 0.5v low, channel dependent. Fluctuations like that is usually due to the alternator, rebuilt ones live in dog years. It ain’t four years new.
 

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Discussion Starter #6 (Edited)
Oh snap.. thats your video! ok, just to wrap my head around it... if i do not see fluctuations in voltage from + alternator and - batt (driver and pass), could that still be alternator? The only reading i have that bounces is from the torque app reading. Also, from your video.. i saw that the threads on the the body bolts make the ground connections. I only cleaned the face of the ends/bolt but not the threads. Worth going back for those? From the video i think i should... I feel like i'm being a bit paranoid really, but the fluctuation makes me think there is a ground or some sort of connection barely hanging on and i'll be camping somewhere far when it finally goes!

edit: I do have my original alt somewhere... i'll try do dig it up. Dreading the belt tab thing already....
 

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The way you're describing the alternator seems like the voltage mine puts out 13.4 - 13.9. I think you're fine, but what are you looking for? A steady 13.7? Also, the grounds you clean, were they corroded or dirty? I think you're fine becasue I replaced an alternator that went bad with a Motocraft OEM, it read 12.9 to 13.1, didn't like the low voltage and put did a warranty swap to get the same thing, bought a Auto Zone alternator and that's the one I see 13.4 to 13.9. I still have the Motocraft OEM as a spare. I bought that Autozone alternator 7 years ago and its still strong. I have not deciphered the charging algorithm, but the truck will cycle the alternator charge on and off.

Have you removed the alternator and cleaned the alternator to manifold connection? One guy was having voltage problems and the bolts were loose.
 

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Discussion Starter #8 (Edited)
I'm looking for 13.7v steady, I have captures of at least being steady at 13.4v at idle, just 2 weeks ago on the torque app. Last weekend i was driving and i would bounce between 13.1 and 13.4 at speed with about 1.5k RPMs, i thought i should be higher. When i first started taking a look at the issue and got greedy wanting 13.7v for my troubles, but now i'm back to settling to a stable 13.4v. Specially sine after the work i've done has gotten to 13.8 at the alternator and both batteries at idle, with the 140amp alt.

No, when i took the chassis/4 body/2block/battery+-/alternator+ connections there was not much corrosion if any, the block ground in the front was a bit dirty. But I will say it did help as it brought the loss of v down to the drivers side battery. Where now the drivers side battery reads the same as the passenger at idle.From what i gather with testing is that i have good connections to for alt and both batteries. I'm wondering if the issue for bouncing v reading is further down from the drivers battery to PCM + or -. Basically trying to find out what the next hop and where those cables are at.

I just read what i wrote... kinda feel like i might of caught a bit of 6.0 paranoia, and a little too much free time on my hands just thinking **** up. I'm going to take it for a drive tonight and see how it does, i will say i have not actually driven it since last weekend.. just tested. I did let it idle for a bit to charge batteries if i happen to start it. batteries ready about 12.66v after sitting overnight.


@TooManyToys Have not taken the time to thank you for your videos! Thanks for taking the time to make them, they've been great help.
 

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If you are not seeing a big variation alternator positive to alternator frame, it's not the alternator. It's how your PCM is reporting.

There's no algorithm with these trucks, with a single alt the gauge cluster turns the alternator on with key-on. With dual, the gauge cluster turns on the alternator through the PCM, the PCM decides which alternator to turn on with glow plugs on, and then both after the glow plugs turn off. Voltage output should be 14.2v cold, drops to 13.6-13.8v when the thermistor heats up. The alternator(s) is triggered on, it's up to the alternator's current output to what the voltage pressure will be, and again, hot it should be 13.8v or slightly below.

I'll give you another video you'll need to speed up. Start at 15:50. Never finished part 2.

 

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I guess the algorithm I think our Ecms must do to our trucks is like the three stage charge my solar system has where when the lead acid. batteries are dead it dumps the amps in, when it gets close, it lowers the amperage, and once it’s charged, it starts a float mode. The truck has got to do something like that to prevent overcharging the battery.

I think this jumping voltage is how the amperage is put in the batteries as the engine controls changes in rpms and power demands.
 

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With a 6.0, all voltage control is done by the voltage regulator in the alternator. The voltage regulator will adjust current output to maintain a voltage.

140a alternator testing.

 

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Discussion Starter #12
I see what you did there :D ----> (I'll give you another video you'll need to speed up. Start at 15:50. Never finished part 2. )

For work i watch a lot of training videos for certs etc... i've gotten used to doing 1.5 or 1.75 speed and still grasp. I do have to stop videos when i take pictures to reference in the garage as i hate trying to rewind videos through my phone. I'm going to watch the video then go for a spin. I'll take a vid of the dash on start process and driving, cold/warm... brush up on editing skills while i'm at it.
 

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ChrisSki, not the best graph to illustrate the compensation in most voltage regulators.

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I get the stuff about the temp compensation, rpms, and pulley size being different. In a solar battery system, all power is pulled from the batteries, and the panels provide enough power to replace what a battery loses. Similar to that, I think the electric power in our trucks comes from the battery, and the power from the alternator is regulated to recharge the battery.

With the amp meter hooked to the battery, the amps can just as well be pulled from the battery as being supplied by the alternator. Only way to really tell where these amps come from is to disconnect one of them, which for any modern vehicle, it’s not good.

I’m not explaining it very well, but I will try to find the article.

Another thing I recently found out is the myth of a parallel battery system pulling equally from both batteries. with two batteries like we have, it’s not terrible, but as you add more it gets much worst. The wires have so little resistance, our parts store ohm meters pick these up as a short, but it’s still there, and battery cells have a few times the resistance of the wires, so once ohms law is used, you can see most of the load is pulled from the battery with least resistance. So if cable length is not equal and crimping are not done well, and the right size wires are not used, the batteries can get killed even easier.
 

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Yeah, our system is not laid out really well. Usually, the connections have a higher resistance than the cable itself as you probably know. It's why I did the layovers and additions I showed in another video, but I was trying to not go down the resistance path at that time as many get lost, but I did later ...... and lost every one.

I use my Solar battery tester to check out batteries when I buy them and try to pair up two as close as possible at the store. It shows resistance and well as the other attributes.

2ga battery to battery was not the best situation, but some can theorize Ford didn't want to. That's another rabbit hole.
 

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Discussion Starter #16
Ok, so i came back from the drive... turned back around before i got to far. Driving down the freeway warmed up i was sitting at 13.1 to 13.2 volts. I then thought about turning on AC or headlights as they would draw more... the voltage would then drop to a range of 12.9v and 13.1v, i hit the AC and it hit 12.8v. I didnt want to keep driving away from home so i turned around. When i was almost home, i accelerated pretty good up a hill and the voltage did not change much past 13.1v or 13.2v. When i got home i jumped out before i shut it off and checked, 13.4v at idle at both batt and +att to - of pass batt and + alt to case of alt, asked someoen to rev it to 2k for me and it stayed at 13.4. The readings were stable even with increase in RPM, which maybe the system is not increasing requests properly? I did read the alt reduces after engine bay heat rises, but i dont think its to where i should get this low.

I also checked the loss from + of alt to the + of the drivers battery to see if there was a difference when it was hot, .04 loss. I'll post the link to video is a sec, i have to upload it.
 

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Only because I got bit on this recently, you should check the cal on your voltmeter.
 

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Discussion Starter #18
Ok, I noted the link to the video below. Its going up a hill i give it a little extra to see if i can see more volts, if volts are being requested properly. Volts is 2nd square on the top row going right to left. Revs is the 2nd square down on the first column. FICM is the 3rd column. At this point i was not testing headlights or AC. At one point it does dip to 12.9v. I'm going to try to replace this alt with my original, its been sitting around hopefully it still works to test. I think i will test with another meter to verify my findings, i've had it for a while.

 
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