Powerboost - Totally Dead

[dejoli]

1FTFW1ED5MFB74627

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[HammaMan]

turned 90 degrees from above....

Amazing what images can do eh? As I illustrated in the above image, match connector numbers like C1617c

 

[scott011422]

That’s odd. Can you take some more measurements for us? Something seems off

with the AUX battery disconnected

what is the voltage to each one of those posts?

 

[dejoli]

All are essentially 0 with the exception of the one indicated above at 12.8. Some will fluctuate from 0 to .01-.02. But that’s it.

 

[HammaMan]

Simplified. Your batt isolator is dead

As I stated, I'd took out my BCMC for easier access behind it -- wasn't difficult, need to take out the fender liner to make it easiest (4 connections and 2 christmas trees on the bottom of it). The B+ is where I tapped for my amplifier 2 gauge connection, required re-shaping the factory crimp as it protruded out far beyond what it needed to. Took out the isolator as well -- it just pulls straight out of the battery tray. It's just a few mosfets stuck to a heatsink, embedded in resin with a lin bus connection to control them. The isolator looks to be 8 gauge on 1 side and 6 gauge on the other. Its only purpose is to charge the big 12v battery -- that's it.

The busbar for the B+, DCDC, and Aux batt is the best location IMO for my amp as it's got direct access to the DCDC(aka alternator) and has an LFP batt connected to it via 4 gauge on the aux side and the big AGM sharing its post via the isolator.

 

[Papa Tiger]

F150 Powerboost 2nd battery problems in back of passenger seat - Search Videos (bing.com)

 

[scott011422]

Simplified. Your batt isolator is dead
View attachment 126561

I don’t disagree, but if the isolator is dead, and there is no aux batt. Where are the fans getting main battery voltage? I’m away from my diagrams till tomorrow.

 

[HammaMan]

I don’t disagree, but if the isolator is dead, and there is no aux batt. Where are the fans getting main battery voltage? I’m away from my diagrams till tomorrow.

Inconsistencies in wiring diagram, it says the 4th post goes to the fan aux box, which isn't populated. There's another wire coming off of the batt itself and it may be to power the PS or ABS even if the BCMC is lost totally. The wiring diagrams are wrong for some reason.

I do know for a fact about the B+, DCDC, and Aux wiring locations as I verified the physical layout.

 

[gb7FRz26]

A bunch of job 1 trucks like mine had fuses that weren't fully seated. Can't remember if mine was under the hood or passenger kick panel but one box was fine, the other one I pushed every single fuse in at least two or 3 mm, like they were just barely seated.
Just throwing that out in there in case. Does sound like your isolator though (sorry).

 

[Pierre.Granger]

Everyone here is doing a great job in trying to pitch in and solve this problem. My truck has been bricked in a similar fashion for three weeks at the dealer. I’m not upset. I know the technology in these things is pretty big. I have a model year 2024 F150 platinum plus waiting in Kansas City for delivery to Granger Ford. My biggest concern is whether we can get my truck running so I could either trade it in or have Ford buy it back. These are awesome trucks with a lot of technology unfortunately, they break down at the same time. Anyway, you guys are doing an amazing job being positive on the troubleshooting!

 

[scott011422]

My vin shows similar. Those two front terminals on mine go to the power steering.

I should have fans on that 4th lug. I have nothing there.

The other wires connected to the positive post of the battery go to the Flywheel starter and the BISG.

The only other thing to check would be the BMS on the battery. If the internal shunt went bad that battery would have lost its ground. Do a continuity check from the center lead post of the negative post on the battery to the chassis ground there by the battery. Make sure to leave everything connected on the negative post.

If that checks good, then that first terminal, C1617A, (B+) should have battery voltage on it. If you connect a jumper cable to that stud first, then connect it to the positive post of the battery, the truck should come alive. If so, Need that isolator.

 

[HammaMan]

The isolator can remain connected to the BCMC while being disconnected from the battery with the vehicle connector removed, you can then pull it out, pop off the cover and check for continuity at it directly.

My belief is that its mosfets are normally closed, but I have not verified this. Ford may have used normally open and just keep them powered closed via the connector. They should be closed at all times sans the rolling start so the connector may need to be plugged in for the verification.

 

[scott011422]

The isolator can remain connected to the BCMC while being disconnected from the battery with the vehicle connector removed, you can then pull it out, pop off the cover and check for continuity at it directly.

My belief is that its mosfets are normally closed, but I have not verified this. Ford may have used normally open and just keep them powered closed via the connector. They should be closed at all times sans the rolling start so the connector may need to be plugged in for the verification.

They are definitely normally closed. Remove the isolator and it still passes power.

 

[dejoli]

Got the truck to the dealer yesterday by pulling and charging the aux battery to 12+V. reconnected and started right up as it should. Will update this thread once a resolution since it appears multiple people have had or are having similar issues.

Appreciate the technology as well, just appreciate it more when it's working

 

[HammaMan]

I think you're the first isolator I can recall seeing die. That's why your situation is a bit different. Their default state is to pass power so for yours to fail open is really unusual.

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