Friday, June 2, 2023


Unprotected wiring in RV catches on fire. Is your RV next?

We wrote earlier about a Montana RVer whose fifth-wheel wiring caught fire, leading to his filing a class action lawsuit. The suit alleges that the manufacturer, Forest River, failed to install a circuit breaker on wiring running from the house batteries to the 7-pin connector box. It also states that the wiring was not properly protected, and that when a short occurred, lacking a circuit breaker, the wiring caught fire.

Happily, the owner spotted the fire and was able to avert a catastrophe by putting it out. The owner later found this was apparently not a random situation. He claims a newer model of the same rig also lacked a circuit breaker—leaving him open to a repeat performance. It raises a few questions all towable RV owners should be concerned about. Could your wiring catch fire? How can you find out if your rig could have a similar issue that could lead to a fire? If it does, what can you do to ensure your safety?

Why did the wiring catch fire?

In the RVer’s fifth wheel, wiring came from the house batteries to the 7-pin connector box. The 7-pin pigtail then allowed current from the tow vehicle charging system to charge the house batteries when the tow rig was running and connected to the trailer. The suit, Jay Nelson v. Forest River, filed in the U.S. District Court of Montana, essentially says that a short occurred when the “hot” wire from the house batteries chafed and came in contact with metal in the junction box.

What the safety standards say

RV manufacturers, including Forest River, who are members of the Recreation Vehicle Industry Association, agree to follow various safety standards. In this case, the ANSI/RVIA Standard for Low Voltage Systems is cited in the suit. The standard says, “All conductors shall be provided with overcurrent protection.” (3-1). Additionally, 3-2 says that such protection, “shall be rated not in excess of the conductors” used in the circuit. The suit alleges that NO circuit protection, neither fuse nor breaker, was installed.

Are there exceptions to where an RV manufacturer doesn’t need to install “overcurrent protection”? Yes, two exceptions are stated. Solar panel circuits don’t need a breaker or fuse, as long as the wiring ampacity is large enough to handle the maximum amount of current the panels could produce. The second exception is for “braking circuits, cranking circuits, circuits supplying lights subject to federal or state regulations, and pigtails of utilization equipment less than 10 inches in length…” Battery charging circuits don’t appear to fall under these exemptions.

The bottom line is this: If a short occurs in an “unprotected” circuit, it could lead to a fire in your RV. So how do you know if the wiring serving your 7-pin connector is safe? Here’s how we checked ours—and the principles are the same for all towables.

Safety at the start

To start, keep safety in mind. Since you’ll be poking around in circuitry, DISCONNECT the battery bank negative post clamp. Since we’re never sure of just how manufacturers wire their systems, it’s not a bad idea to disconnect from shore power and shut down solar power.

Chasing down wires

The search is on. You’ll start by chasing your 7-pin connector pigtail back from where it connects to your tow vehicle. Follow the pigtail back to the junction box. Here’s where Jay Nelson of lawsuit fame found his first issue. The junction box should be protected against the elements. His junction box resembled a common metal electrical box, like you might find inside a home. Unfortunately his was exposed to the weather—strike one, in his opinion.

wiring caught fire
Here’s what we found. Junction box to the left of two circuit breakers. The top breaker has one feed wire going into the junction box. R&T De Maris photo

Also running to the junction box will be a hot (positive) wire from the rig’s battery bank. Here’s where you’ll get to do a bit more physical wire tracing. Somewhere between where the battery hot wire connects to the pigtail wire that ultimately connects with your tow vehicle charge system SHOULD BE a circuit breaker, or (unlikely) a fuse. You can see in the photo a circuit breaker on our rig. One wire connected to “battery” side of the breaker is from the battery bank. The other terminal, typically labeled “aux” or “auxiliary,” leads to the tow vehicle charge wire in the 7-pin pigtail. Jay Nelson’s lawsuit says there was NO breaker in that line on his rig.

Got a breaker? Good! But check it, too

wiring caught fire
30A indicates 30 amp capacity for this breaker. R&T De Maris photo

Found that breaker? That’s a good start. Check the breaker for the rating—the maximum amount of current it will pass before opening and shutting down the circuit. That information will be printed on the side of the breaker. In our case, the breaker was a 30-amp unit. The size of the wire coming from the battery bank was 10 gauge. Similarly, the wire running from the breaker to the inside of the junction box was also 10 gauge.

The question now is, what does that battery bank “hot” wire connect to? You’ll need to pop the lid off the junction box to see. We had to fish out a lot of wires from the junction box, and identify the hot wire coming into the box—in our case, two wires attached to the hot wire: a black 10-gauge wire, and a blue 12-gauge wire. Assuming our manufacturer followed “traditional” wiring colors for the pigtail, that big black wire was the “hot” running out to the tow vehicle. This would be the one Jay Nelson says melted on his rig. The smaller blue would be electric brake circuitry. Presumably this one travels out to the emergency breakaway switch, shooting power to the brakes if the breakaway switch was tripped.

Is this hookup “code” legal?

In this hookup, these two wires are being protected by a 30-amp breaker. The ANSI/RVIA Standard tells us in Table 1 that 10-gauge wiring has an ampacity of 30 amps, while 12-gauge has a 20-amp limit. The 10-gauge charge wire is fine; but some might question the 12-gauge wiring being “protected” by a 30-amp breaker. There’s one of those exceptions—the blue wire for the “braking circuit” technically doesn’t require any over-current protection, so the design would seem legal.

How’s your wiring?

So how about your wiring? Is the wiring from the battery bank to your 7-pin pigtail protected by a circuit breaker? Is the wiring “downstream” from the circuit breaker big enough to handle the amount of current that the breaker will pass? If those two conditions aren’t met, then something will need to be done. You don’t want to risk having your wiring catch fire.

But what to do? If your RV is an “orphan,” that is, the original manufacturer is out of business, you’re definitely on your own. If the manufacturer is in business, our first advice is to call them and explain your findings. Ask them to fix the problem at their expense. If they refuse, you’re on your own—but you might consider shopping for an attorney.

Need to fix the wiring on your own? You’ll need to install either a new circuit breaker, or one sized to properly protect the wiring the battery bank is attached to. If you’re not sure of what you’re doing, by all means, hire capable help. A circuit breaker will need to be installed in a weather-safe way. In our rig, the pigtail junction box lies outside the rig, under the floor, but protected by a corrugated plastic underbelly shield.

Glad we looked at ours

wiring caught fire
R&T De Maris photo

Incidentally, we were happy that we went to the trouble of doing our own inspection. While the circuit breaker was there, and was sized appropriately, we still found problems that could have caused us grief. The circuit breaker shell was tightly mounted to the trailer frame. But for whatever reason, the actual breaker was completely detached from the shell. The wires to the breaker just held it in midair.

While not seemingly likely, if the breaker had twisted “just so,” the exposed terminal on the battery side could have come into contact with the frame, resulting in a short. Or, the guts of the breaker could have bounced back and into contact with the very nearby frame. Since “upstream” from the breaker is the battery itself, nothing would have stopped the current flow until the wire conductor itself melted, and fire was a real possibility. Inside the dead space underneath the rig, a fire could easily rip right into our bedroom. A trip to the auto parts house and an outlay of less than $10 bought us a new breaker and peace of mind.

An inspection will take a little time and effort, but knowing that your circuits are properly protected will help you sleep better. Don’t let unprotected wiring catch fire!



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1 month ago

My rockwood mini lite has the metal junction box and the circuit breakers outside the box. Located on the underside. I’m not particularly concerned about the metal jbox since it’s low voltage wiring. However leaving the circuit breaker terminals exposed does give me pause since I drive in the winter months which means salt and snow certainly splashes up there. I’m thinking about creating and installing some sort of a mud flap to mitigate that problem. Also i will make cleaning each terminal with contact cleaner part of my preventive maintenance regime.

Robin P
1 month ago

I’ll be checking this today and also replace the metal box with a weather proof one. Why would they use a traditional metal box knowing it’s exposed to the elements, cheap!

James Collins
1 month ago

The bottom line is electrical wiring needs more than just over current protection. It also needs protection from chaffing and abrasion, harsh chemicals and salts, hot surfaces, lack of support, over flexing and strain, chewing and gnawing from rodents. Even the 12V breakers pictured in the article have exposed unprotected attachment wire and cable connections. Ideally, nothing energized in the electrical circuit would be uninsulated or exposed such that it could become short circuited. Arcing and sparking alone can be enough to cause a fire without a circuit breaker or fuse ever opening up.

Neal Davis
1 month ago

Thank you! I’ll see how our Jeep is wired to tow.

1 month ago

On my 2017 Winnebago Trend (purchased May 2016) while under it (April 2018) I found that the 50-amp breaker had detached from its shell just like you found on yours. I also replaced it with a new breaker. All the wires were exposed to the elements but tucked up and attached to the cross frame.

Robert Pulliam
1 month ago

You stated the manufacturer followed normal procedure in the color codes of wire, but a black wire for hot is only used in AC wiring. Normal hot wire color in DC wiring is red, black is ground, other colors are used in auxiliary circuits but red is always hot or positive.

Bob M
1 month ago
Reply to  Robert Pulliam

In DC wiring if A black and white wire is used, then the black wire is hot. If a black and red wire are used, then red wire is hot.

Bob P
1 month ago
Reply to  Bob M

I stand corrected, in my 65 years of working on my own vehicles that’s a new one on me.

Mark Marder
1 month ago

Excellent and valuable article.. That junction box in my 5th wheel is exposed to the elements. How can that be solved? If it were totally sealed, would there be a heat problem? Does it need air circulation?

Bob M
1 month ago
Reply to  Mark Marder

You would have to use a waterproof box. Wires in the box should be stranded wire with no outer coating. What I mean by outer coating is for example, an extension cord that is orange. the orange is the outer jacket. Inside their are 3 wires, a black, white and a green. These 3 wires in a box will not heat up as long as there is no outer jacket around the wires in the box and controlled by the right size circuit breaker. The orange extension cord is only used as an example for understanding purposes.

1 month ago

Valuable article. To help follow along in the discussion, I suggest that when reprinted again, the article’s first picture have the wires passing outside the picture labeled to reflect the current flow either to or from the external component to which it leads.

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