Tuesday, March 21, 2023


My inverter only powers one outlet. How can I rewire it to add more?

Dear Dave, 
I have an inverter in my new camper and despite repeated requests I cannot get a wiring diagram for the camper. The inverter only seems to power one poorly placed plug—not even the one for the shaver in the bathroom! The inverter is basically useless. I’m planning on rewiring it. (I’m the son of an electrician and an electrical engineer—so I probably won’t electrocute myself. 🙂 ) But I wonder why the manufacturer won’t give me an electrical diagram. Apparently even the dealer can’t get one. Any helpful info? Thanks! —Tom, 2021 Heartland Mallard Pathfinder

Dear Tom,
This has been an issue for years as most manufacturers have a rough diagram that is a guide for the manufacturing process. However, the units are hand-built on the line and things change on a daily basis. Winnebago does have the best diagrams and 3D diagrams head and shoulders above the rest. But they still have some vague areas that are hard to determine where wires go.

Wiring diagram from Thor

Here is the wiring diagram I got from Thor when trying to put in a new set of lithium batteries and a new converter. I had better drawings on a napkin when I built my first garage!

I believe the dealer can get a generic set like this one, but it really doesn’t help much. Plus, most dealers don’t want the manufacturer to send drawings to customers as they want you to go to the dealer for repairs. And then there is the issue with liability for the manufacturer.

We had the same issue with the 2015 Thor Challenger with a 1800-watt inverter, trying to find what it powered.

We charged the batteries, unplugged the unit from shore power, and made sure the battery disconnect was in the closed position, which means it allows 12-volt power to go through. Then we took a noncontact voltage tester and GFCI plug-in tester and checked all the outlets. We found the residential refrigerator outlet was live, and the outlet for the outside TV, the bedroom TV, and the two outlets above the theater seats were all live as well. The outlet for the living room TV was not, as well as any other outlet in the kitchen, bathroom, or bedroom.


Recent article on inverters

I just posted an article about inverters and wiring routing, which you can find here.

By RVIA code, outlets that are within a close proximity of a water source such as the kitchen and bathroom need to be protected by a ground fault circuit interrupter (GFCI). So typically those outlets would not be connected to an inverter.

From what I can find on spec’s, the unit has a 1200-watt inverter and 110-watt solar panel. Most of the trailers come to the dealer with no batteries standard, so the dealer adds the batteries to match what the customer needs for power. If you have one group 24 battery, then I would believe you might only have enough 12-volt power to supply one outlet.

If you are planning to upgrade and add outlets to the inverter, check to see if the inverter has a pass-through feature. That means when the unit is connected to shoreline power, the inverter automatically switches and allows 120-volt power to pass through it to the outlets rather than draw from the battery.

I don’t think you will need a wiring diagram, as the current outlets are wired to the distribution center with residential-style Romex, which you are familiar with. Remove the wire from the circuit breaker it is connected to and use a certified junction box to run Romex to the inverter. You will find a wiring diagram in the previously mentioned post.

Note: I would not recommend this as a DIY project for the average RV owner that is not a licensed electrician. Just a disclaimer to CY(or M)A.

Good luck, and let us know how it comes out, with photos if possible.

 You might also enjoy this from Dave 

When plugged into 50-amp, why doesn’t inverter power some items?

Dear Dave,
We have a 2015 Fleetwood Bounder 35K and are having issues with the Magnum inverter. We are connected to 50-amp shore power. The following don’t work: auto steps, TVs, radio, one outlet under coach dash. What is wrong? Do you have any suggestions? We have replaced the Magnum remote control and it’s still not working. There is also a solar panel, but we can’t figure that out either. —Caren

Read Dave’s answer.

Dave Solberg is a leading expert in the RV industry and the author of the “RV Handbook.”

Read more from Dave here


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1 month ago

Same as Tommy – Used for purposes of short term boondocking, one simple way to be able to distribute the inverter’s 120v power output throughout the RV is to mount the inverter near it’s battery bank source and route the inverter’s output outside of the RV using a robust external extension cord fitted with an adapter plug fitting the RV’s exterior power inlet. In this manner your inverter’s power is distributed thruout the RV’s breaker panel. Before turning the inverter on you should turn off the breaker that powers the RV’s charger to avoid charging the batteries with their own power. And be mindful of the wattage you draw from your inverter. Just because the inverter’s power is now routed everywhere does not mean you can run everything.

Steve K
1 month ago

If you can find the output from the inverter you can tie it into the main power via an Automatic Transfer Switch similar to the WFCO T30. Just disconnect the shore power from the main panel, attach that to the normally connected (NC) input on the transfer switch. Then attach the inverter to the Normally Open (NO) input on the transfer switch. The output of the switch goes to the main power on your panel. If you have a converter (battery charger) on the main panel, disconnect that, add an inline breaker and connect it to the NC input on the switch. That way you do not try to charge the battery using the batteries own power. I have an on-board generator so I have 2 transfer switches. The shore and generator power go into the first switch, the output of that goes into the NC on the second switch along with the inverter. It’s nice not having to run the generator just to make a cup of coffee.

Thomas D
1 month ago

Your dads an electrician and a engineer and you write to dave? You PROBABLY WONT ELECTROCUTE YOURSELF.
Man, you didnt learn much at your fathers knee did you? Best if you stay away from electricity.
Call your dad!

Diane McGovern
1 month ago
Reply to  Thomas D

Hi, Thomas. I think Tom’s question was basically regarding where to obtain a wiring diagram. I doubt that his dad would have it. Just sayin’. Have a great day. 😀 –Diane at RVtravel.com

Dan M
1 month ago

My Grand Design Imagine XLS has an incorrect label on the breaker panel. I have a 12v fridge but one of the circuits was labeled fridge. I spoke with customer service to try and find out what that breaker actually went to and they had one of their engineers call me back. He apparently even asked around but no one in their engineering team even knew how they wired them. Their suggestion was to tell me to turn of the breakers and then go around the camper to see what turned off. They don’t even have plans in their design or engineering department for how they’re supposed to be wired. Eventually discovered that breaker powers the AC to DC converter which is why nothing appeared to turn off, because with it off the battery still powered everything 12v. It also turns out the fridge has an in line fuse somewhere because it doesn’t go to any of the 12v fuses. Very confusing and frustrating.

Jim Johnson
1 month ago

Easy inverter for small trailers that lack one-

Pretty much any trailer that has a factory installed TV antenna has a coax outlet with a built-in switch to send 12vdc power to the antenna’s amplifier. This outlet may or may not include an automotive style 12vdc power socket. If not, the socket version is inexpensive and a fairly simple swap.

The power socket will usually support 9 or 10 amps. Multiply the socket’s maximum amperage by 12 to convert to watts. This will be the maximum power that can safely be supplied. 100 watts is a pretty common size inverter. Don’t buy the cheapest inverter you can find. Such devices often do a poor job of creating a smooth and noise free alternating current. At the same time, you likely don’t have to buy a top of the line inverter either.

What can you do with 100 watts? – run a fan, a small TV, recharge cell phones or laptops. Lots of small devices that make dry camping more convenient.

Tommy Molnar
1 month ago

My answer to this problem was simple – to me. I ran a large extension cord from my inverter to the cord storage box (my trailer is old enough to have that storage spot), constructed a box to plug the extension cord into the shore power cord, and bingo. Power to all the ac outlets in my trailer. I’ve done this with two trailers over a 25 year period and have never had an issue of any kind.

Don H
1 month ago

I’m not sure what you think is wrong with that wiring diagram, Dave. It’s exactly what you would see for wiring a house…

Gordon den Otter
1 month ago

The diagram you show here is a typical architectural drawing. It ONLY shows which lights are controlled by which switches, and where the outlets go. It does not say or imply where the wires go. That is left to the electrician to figure out. As I’ve discovered in my own house, you’re even lucky if the electrician bothered to correctly label your breakers!

Bob p
1 month ago

Bounder doesn’t have wiring diagrams. When I called customer service to track down why my coach batteries were not being charged while driving by the relay that handles that chore, I was told that 6 teams take care of wiring units and all of them use their own technique for wiring. They said it was wired per the schematic but there wasn’t a wiring diagram showing where the particular wire was routed. I ran a new wire from the relay to the batteries, problem solved.

1 month ago

The first manufacturer to receive ISO certification will be the winner. Why RV manufacturers aren’t required to be presently is strange since vehicle manufacturers are.

Bob M
1 month ago
Reply to  volnavy007

ISO certification is voluntary. RV manufactures probably don’t have much documentation which would make it hard for them to get certified.

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