FWC running lights issue

[BenW]

I have a 2022 Hawk side dinette on a 2018 Tundra double cab. I recently paid an experienced van electrician to install a Victron DC/DC charger, a 200ah SOK lithium battery, Victron solar controller, and Renogy panels. The DC charger is hooked to the truck via 4awg wire and a new Anderson connector + an additional connector specifically installed to provide power to the the running/marker lights. I brought it home yesterday and I thought everything was working great until I noticed after it got dark that the rear red LED running/marker lights were glowing even though the truck + truck headlights were off. I went outside and turned the headlights on and all of the driving lights came on but flickered. After turning the headlights off, the red running lights at the rear of the camper continued to dimly glow until I went into the camper and disconnected the battery via the big red switch you can see in the photo. What is going on here? I understand that with the new wiring done, there could be a bad connection now between the running lights and the truck but why would the battery connection have any impact on the rear red led lights?

I can see the green wire that is labeled "running lights" which was originally wired to the Atwood plug. It is now wired to a 5 amp inline fuse which is then wired to a new plug (I'm not sure of the type) installed specifically for the running lights. On the truck side, the new plug is now connected to the original wire installed by the FWC dealer which runs to the back of the truck and taps into the driver side truck marker light. This all makes sense given what I've read on this forum about the running lights. But again, where does the camper battery come into play here?

For the time being, I have taken out the 5 amp inline fuse which has killed all power to the running lights. The van electrical guy is out of town for the next two weeks and I have a trip coming up that I'd like the running lights to be working for. Any help you all can provide would be much appreciated!

 

[Jon R]

I’m guessing that you have the isolated version of the dc to dc charger and your electrical guy did not positively connect the ground of the truck to the ground of the camper. That has the effect of powering your running lights from the positive of one battery and the negative of another one, with no other connection between the batteries except a tiny level of stray current via the air or incidental structural contact. The LEDs glow from that timy level of current.

The charger will say “isolated” or “non-isolated” on the front. Another obvious way to identify it is the isolated one has four wire connections (two positive and two negstive) while the non-isolated one has three (two positive and one negative).

If you can confirm this is the case I can describe easy ways to fix it until your electrical guy does something more permanent.

 

[BenW]

Thanks for the quick response! I have the Orion XS 12/12-50A DC-DC Charger installed, which is non-isolated. I ordered it myself as I wanted the more compact size, heat reduction, and ability to directly take 4awg wiring.

 

[Jon R]

Well if it’s the non-isolated charger my theory above about why your running lights are behaving the way they are is not correct. Let me stew further upon this and I’ll post if I come up with any ideas. I suspect Vic and others will see this soon and may have suggestions.

 

[Jon R]

Set aside the details of the running light wiring for now. Can you describe the 12 volt negative wiring arrangement between the truck battery, the specific dc to dc charger connections, the camper battery, and the negative bus bars? Can you do the same for the positive?

 

[BenW]

Negative
Truck battery to Anderson connector to DC charger to camper battery
NOTE: Does not connect to negative bus bar.

Positive
Truck battery to Anderson connector to DC charger to camper battery

I don't understand why you wouldn't wire the the truck battery to the negative bus and then to the DC charger? That seems like it could cause an issue with the running lights since they are receiving power from the truck but grounded only to the camper at this point.

 

[Jon R]

Negative
Truck battery to Anderson connector to DC charger to camper battery
NOTE: Does not connect to negative bus bar.

Positive
Truck battery to Anderson connector to DC charger to camper battery

I don't understand why you wouldn't wire the the truck battery to the negative bus and then to the DC charger? That seems like it could cause an issue with the running lights since they are receiving power from the truck but grounded only to the camper at this point.

That’s why I wanted to better understand how it’s wired. If there is no connection of the camper negative bus bar to the camper battery negative terminal, none of the camper DC equipment would work. Did I understand your description correctly?

 

[PaulT]

It sounds like Jon may be right about the isolation & that the electrons for the marker lights arrive from the truck on the marker light wire but have to search for a return path via any camper ground conductive metals that are touching truck ground conductive metals.
As a clear return path was not provided, electrons must return by whatever path they can find. Without a gas tight path for return current, the return path is likely intermittent which could cause the computers in the truck issues. I have a 2010 Tundra double cab & the truck computers control just about everything with the lights.
It may be that not having a solid return path causes the truck computers to misread signals.
Try providing a good connection between truck & camper grounds with a separate wire to see how that affects the symptoms. Connect jumper cable negative cable from camper battery negative to good chassis ground on truck. Some small arcing may occur on connecting them so do it with truck parking lights off. The Tundra has a fuse in the circuit to the towing socket connector.
Turn on the truck’s parking lights & observe dim lights you reported in original posts.

Good luck. These can be a bear to diagnose.

Paul

 

[Jon R]

Same suggestion I was going to make, but with maybe a 10 amp fuse in line in case something wacky is going on.

 

[Vic Harder]

Good advice so far, and I'll add my recommendation to bring the 4AWG ground wire to the buss bar first before connecting to the DCDC.