Under hood / under bonnet fuse box help needed

[dkjau]

Help needed please
Working on a mates Sept 22 Everest today. Was tracing out aftermarket wiring for him as he is the new owner of a vehicle set up by someone else for off road camping etc.

Didn’t disconnect anything factory. Had doors, tailgate & bonnet open for a few hours. Went to start it & push to start, screen etc dead. No headlights, brake lights or central locking. Things you’d expect to work without accessories on.

Power to drivers seat all good. Battery at 12.6 volts no load. Came up to 12.75 on charger for 15 min but still no start up power to dash or push button. (Have since discovered earth clamp was on wrong side of BMS so hoping 8hr overnight solves issue.)

Trying to work out if it’s to do with BMS or something else. Fusebox under bonnet has power. Fusebox under steering column doesn’t appear to but that may be normal, no power to 12v pin on OBD connector. All four BCM fuses under the bonnet are fine.

Tried disconnect for a few minutes. Tried charging battery - though only discovered video on charging with neg clamp on chassis side of BMS this evening. Have left on charge for the night with charger neg to chassis earth lug.

New battery in key fob.

Anything I’ve missed if it does not start in morning?? Otherwise it’s a flatbed on Monday.

Has anyone ever taken top tray off the Fusebox to add wiring who can tell me what’s under there or how to get into it? After market wiring has been run under the fusebox. Don't think that's the issue, just wondering if moving it around while tracing where heavy duty cable runs has done anything.

Thanks

Dave

Sponsored

 

[dkjau]

Update. Didn't start up this morning. Checked every fuse in under bonnet/hood fuse box. Main fuse to cabin (large one at top of cabin fuse tray under console) is intact.

Seems to point to an issue with BCM either having gone into a low voltage shut down. Run out of other options. Cannot find a physical issue & didn't really do anything yesterday that would have caused it.

Interesting to note that original owner replaced battery when vehicle was less than 12 months old. Wondering if this has happened before.

DJ

 

[dkjau]

Started the morning with a rethink of what I did yesterday to try & work through the process and what may have been the issue. Metered every fuse again & had not missed anything yesterday. All intact. Very few with voltage though.

Kept coming back to the under bonnet/hood fuse box as it was the only piece of factory kit that I touched - and then only briefly.

Yesterday when chasing after market wiring I’d thought it would be easier to trace it and tidy it up if I could sort out what they’d run beneath the fuse box between it & the wheel arch.

I undid the three bolts circled in red in first post. Placed below again for reference.

The fusebox didn’t move so I did them back up. Felt soft to tighten but figured they may only be into plastic & didn’t want to overdo it. I worked in electronic engineering in product development for GMH in 90’s - wouldn’t have been surprised if they were into plastic.

Today in the shed with the help of an auto elec neighbour we worked through the process of elimination again.

With 2 sets of hands some things are easier- like Dan’s idea to bypass the box direct to left side kick panel wiring. Green on white power wire- directly to battery with some 4mm. We got back under column fusebox power & some functionality.

Figuring we’d come back to the under hood fuses again and not being a believer in coincidence we set about pulling the fuse box apart.

Once the two moulded bus fuses are off the front it was fiddly but working around all the locking clips the top tray finally came up.

The bottom side of the top was pins corresponding to fuses above. We metered some & they were straight through.

A dry joint on the board the fuses insert to?? Seemed unlikely. This Everest has done a lot of off-roading. Would have declared itself ages ago surely? Besides you couldn’t get to the board as the bolts had clip over keepers locking top to bottom without getting destructive.

I started looking at the connection from fuse tray to harness. Three plugs with a matrix of female terminals. It seemed the top just socketed into bottom.

One of the three had free play though. I mentioned it to Dan as it clicked into the base of the box. He wondered out loud.

Turns out the keeper on those bolts caused the issue. If you undo them, the keeper stops the bolt rising. All it cans do is push the multi-spade connector off the bottom of the fuse board. It clicks lightly into the bottom of the fuse box as it does it. The one that stayed loose was the giveaway!! Closest to the battery it was the one still connected giving power to drivers seat only.

Turns out there’s just enough free play in the three if you release them from the claws in the fuse box base to allow them to be inserted onto the fuse tray. (Also bottom of lower box is where you find the bolts retaining it to the wheel arch in case you’re wondering. B@$tard if a job if you do have to move it.)

Then you bolt the plug up to the base for all three. Captive steel nuts in plugs mean you can get them tight.

Drop the top tray back into its clips, replace bus relays onto side facing the motor & time to test.
The Everest lit up & started.

Was never to do with BMS or other straws we clutched at yesterday. It was exactly what it looked like. Lack of power to cabin. But not why I thought. No blown fuses. Just three 7mm bolts that if you ever undo them will kill power.

Nothing on the internet or manuals online, no YouTube that I can find that would have solved the problem so here’s my tale for the next poor sod who undoes this bolts.

Sorry. Haven’t found this problem or solution il on the internet or YouTube anywhere. Didn’t take pics. Detailed description should be enough.

cheers

Dave

 

[joprato]

Thanks for sharing ! Will definitely keep it in mind if I ever try and mess with some wiring on (hopefully not) my car

 

[superj]

Wow, what a bummer to have to figure out after an issue. I am glad you guys are good enough on electrical to have found it

Sponsored