2021 FC Blowing 2021 Silverado “Trailer Battery” Fuse

[Dr. Ohat]

Hi all,

Looking for some diagnostics help. 2021 25’ FB FC, 2021 Chevy Silverado LTZ. Getting ready for our 4th weekend trip, so still newbies.

Hooked up TT last night including 7-way plug, left 30amp shore power on; maybe that was my first mistake.

As we tried to depart today got a “running light out” warning on TV towing screen, and TT brakes were locked up, TT running lights were not working, but brakes and hazards were ok.

Checked all fuses on TV and found TV “Trailer Battery” 30amp box fuse blown. No other fuses on TV, TT or TT battery compartment blown.

Got 3 more 30amp box fuses for TV. Installed fuse, hooked up 7-way plug only (not rest of hitch stuff) all lights worked, no warnings on TV trailering page. Finished hooking up and got ready to pull out again, no brake lock ups, but then running lights not working again, and now TV trailering page says “no trailer hooked up”.

TV “Trailer Batter” 30 amp box fuse blown again. Different symptoms now as the 7-way is not registering at all on the TV.

Checked all fuses on TV, TT and TT battery compartment, no other issues.

Have replaced the TV fuse, but not hooking up again until i can determine what on the TT or TV is blowing that fuse. Not sure if that fuse is to protect the truck from the trailer or vice versa.

Any thoughts? Can still preserve the weekend trip!

Thanks,
Greg

[uncle_bob]

Hi

What's the year on the truck? Is your setup factory wired or is it aftermarket?

Bob

[tbrowne]

Blowing the fuse indicates there is a short in the wiring somewhere. Either in the truck or the trailer. Short circuits can be difficult to troubleshoot so a trip to your Chevrolet dealer might be the place to start. The truck is under warranty so the fix should be covered if it's the truck. If the dealer says the truck is OK then I'd let the Airstream dealer look at the trailer. Same deal - it's under warranty.

[Dr. Ohat]

Copy on short, hoping to work thru where it is. Going to try to hook up 7-way with a new fuse in the morning and work thru the 6 circuits 1 by 1 to hopefully see which is tripping the breaker. No issue with the TT not hooked up, so seems it is in the trailer.

Uncle Bob - 2021 with tow package factory installed, so it will run thru and test all the trailering lights, but right now with TV fuse blown the TV won’t even recognize that a TT is connective via 7 way.

[uncle_bob]

Hi

Did the cable to the 7 pin get smashed?

Bob

[Dr. Ohat]

Not that I am aware of or can see, only thought there is that it runs under the propane tank cover and under a small and sharp cut out on the bottom of that aluminum side. But so new it’s hard to believe that it could chaff that much already.

[Dr. Ohat]

Looked again and don’t see any damage to the pin or cable

[uncle_bob]

Originally Posted by Dr. Ohat

Looked again and don’t see any damage to the pin or cable

Hi

Ok, standard drill is to start at the truck and work from there. Plug in any of the normal "test plugs" that act like a trailer and see what it says. Make sure the fuse does not blow. If the fuse does blow then the problem is in the truck. If voltages are not showing up on the test plug, the problem is in the truck.

https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1

If that all works, next suspect is the 7 pin and cable on the trailer. Dive in to the DC bus in front of the trailer and disconnect the charge wire that goes to the 7 pin. Plug into the truck and see what happens. If things still go tilt, proceed to pull the other wires. The last wire you pull before the fuse stops blowing is the problem child.

Once you find the magic wire, track back to the light it's hooked to. It's a good bet you will find a loose wire nut (or something similar) right at the light. If it's the charge wire, you have something wrong with your DC setup ( like a dead trailer battery).

Bob

[Dr. Ohat]

Thanks Bob, used my 7 pin tester this morning again, not getting the readings per the lights that it should. 12V light is working on the tester and not blowing the fuse, but the other lights are not working as they should with turn signals, reverse, etc. Also seeing infinite resistance on the digital mtg on the 12v truck circuit. Truck is at the dealer to get checked out now, hopefully that is the issue. Digging in under the front bed now to open up access to the 12V distribution panel so I am ready to follow that thread as needed. Thanks, again, will update once i hear on the truck.

[uncle_bob]

Hi

One possibility is that a short in the trailer took the truck stuff out.

If you have a way to put a current limited signal into the 7 pin (there are a couple of ways ...) you might check and see what happens on each of the various pins. Not much else to do while waiting for the truck ....

Bob

[Dr. Ohat]

Bob,

Truck getting fixed with a new light and battery module. Can’t help worrying though that i still have an issue in the TT that will blow the fuse and fry the modules again. you mentioned putting a current limited signal into the 7-pin. I have digital multi-meter, but nothing more than that. What do you recommend to do this?

[uncle_bob]

Originally Posted by Dr. Ohat

Bob,

Truck getting fixed with a new light and battery module. Can’t help worrying though that i still have an issue in the TT that will blow the fuse and fry the modules again. you mentioned putting a current limited signal into the 7-pin. I have digital multi-meter, but nothing more than that. What do you recommend to do this?

Hi

I'd use a power supply with a current limit on it. It would also have meters so you could see exactly what was happening. You might have a buddy who's into electronics that could loan you one.

If that's not an option, you rig something with whatever you have. String something like a 12V light bulb in series with the supply ( battery charger, battery, ....). Probe each circuit on the 7 pin and see how much current is pulled.

The main gotcha is that something is loose. All is fine just sitting there in the driveway. As you bump down the road the wire hits this or that and there is a short. The module in the truck *should* be able to handle this with no problems ....

Bob

[Dr. Ohat]

Bob,
Thanks for the help. Had coachnet tech come take a look and confirmed a short in the brake circuit somewhere downstream of the dc power distribution panel, and he would not go further. Since it is new and under warranty I am going to have AS take care of it. Truck had two power modules replaced and I am not plugging in the AS again until it’s fixed. Really appreciate the help, i learned a lot on this one so will be a bit smarter next time!

[uncle_bob]

Hi

Pulling wheels to check wires to magnets is not a lot of fun ... It is something a local garage can do. Just how it gets covered under warranty is a "that depends" sort of thing. If the brake assembly is the issue, it has it's own warranty separate from the Airstream warranty.

My guess would be that there's a problem in the wiring rather than the brakes themselves.

Bob