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Ask 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

Dear Caren,
Since you did not give the size of your Magnum inverter, there will be some assumptions here. But we should be able to point you in the right direction. According to several listings for used 2015-era Bounders, it looks like you have a 2000-watt version that will run several items from the house batteries and also is the charger for your batteries.

How the Magnum inverter operates

So let’s first look at how the Magnum inverter is designed to operate. When you are plugged into shoreline power, as you have indicated being 50 amp, the inverter goes into standby mode and just lets the 120-volt power pass through. At this time it also has a battery charger that provides a multi-stage charge to the batteries.

So, if you are plugged in, any 120-volt appliance or outlet such as the TV and the outlet under the coach dash should be working. I assume the auto steps you indicated are the entrance steps. Those are typically powered by a 12-volt battery and, in most cases, the engine battery. It has an automatic retract if the engine is started—which usually only works for about 2 days after the warranty runs out. The radio is typically powered by the house battery. So both of those should be working off the 12-volt system and not powered by the inverter.

When you are not plugged into shoreline power or the generator is not running, the inverter will draw 12-volt power from your house batteries and provide 120-volt power to specific outlets.

What to look at when plugged into shoreline power

So, if you are plugged into shoreline power, the first thing I would look at is the circuit breakers for the TV and outlets, and the 12-volt fuse for the steps and radio.

Next, take a look at your inverter. There is an AC in and AC out connection, as well as a red (12-volt positive) and black (12-volt negative) terminal.

When plugged into shoreline power, you should be able to use a non-contact voltage tester and verify the AC in and AC out.

You provided a list of things that are not working but not a list of things that are. I assume other 120-volt components are working, like the refrigerator. It looks like you have a residential model, from the brochures I was able to find, as well as the microwave oven. How about 12-volt functions such as the lights, vent fans, and water pump?

Other possibilities to check

Again, since the inverter should just be a pass-through, the 120-volt power should come in and go out and everything should work. If nothing worked, I would suspect the inverter has shut down and needs to be reset. You can verify this by looking at the inverter, which has an on/off button and green indicator light. If the light is not illuminated and you have 120-volt power coming in, it could be an AC overload condition that turned the inverter off or an internal fault, both of which can be reset.

If you have 120-volt power coming in and not out, and the green light is blinking, it means it is in search mode.

Research the inverter in the owner’s manual

I would suggest doing some research on how the inverter works and what it powers. You should have an owner’s manual. If not, you can download one here.

It is important to find out which outlets the inverter provides 120-volt power to and if it is actually getting 12-volt power from the battery. This needs to be done with the unit unplugged and with fully charged batteries. Keep in mind this inverter takes 12-volt power from the house batteries and supplies 120-volt power to specific outlets. It does not supply 12-volt power to any of the functions that is done through the batteries and 12-volt fuses. When you are connected to shoreline power, the inverter goes into standby mode and allows the 120-volt power to pass through to the distribution center. It also charges the batteries with a multi-stage charge.

The inverter remote

You indicated you replaced the remote. Typically this is just a display that tells what charge is coming in, what state of charge the batteries are in, and allows you to switch modes. It does not affect the operation or flow of power to components. Check out the manual to see the remote.

On the inverter, there will typically be a red (positive) and black (negative) cable coming from the battery. Verify with a volt meter that you are getting 12.6 volts to the inverter.

You can use a non-contact voltage tester to make sure there is 120-volt power coming out of the Romex wiring coming out of the AC exit port.

Residential refrigerator

Looking at several online videos, it looks as though your model came with a residential refrigerator. That means it needs 120-volt power either from shoreline or with a larger battery bank and inverter like the one you have. When you are not plugged into 120-volt shoreline power, open the refrigerator. If the light is on, it runs off the inverter and batteries. If not, you need to make sure you protect the food inside.

I think that if you spend some time figuring out what components are powered by the inverter and how it operates, you will be able to track down the non-working components and find they are probably not the inverter, but rather a fuse, circuit breaker, or even GFCI outlet tripped.

Solar panel

Also, I don’t think the solar panel has anything to do with your power issues as it’s simply a 12-volt charging system. And if it’s just one, it’s probably a small trickle charger to keep the batteries topped off when not plugged in.

Keep us informed and provide any information you can on the troubleshooting.

Dave Solberg is a leading expert in the RV industry and author of the “RV Handbook” as well as the Managing Editor of the RV Repair Club.

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Larry Lee
28 days ago

I have the same Magnum inverter you describe in the article. It has a small metal panel located just next to the 120 volt input & output cables. With the unit unplugged from shore power, you can easily remove this panel with a screwdriver and check the wirenut connections inside. Mine were poorly installed and black from overheating. Cutting off an inch or two to obtain good wires and properly installing the wirenuts solved my electrical problems.
Also, on my brand new 2014 Thor Tuscany xte 40EX the rearmost battery cable which at first glance appeared to be properly installed, was actually just placed down in the battery post and not actually connected! No wonder it was not charging correctly.
Manufacturing errors such as these are inexcusable in my view, but as owners we must be thorough in our routine inspections and trouble-shooting making no assumptions that the work has been done correctly.

Quin
28 days ago

Have the maintenance department check the supply tower. We recently changed spot within the same park and had similar issues. Simple fix.

Thomas D
29 days ago

You might mention that a non contact tester will not work on 12 volt DC also mmm

Steve
29 days ago

Most inverters only provide 120 v power to 1 leg of the system. A 50 amp trailer needs 2 hot legs to power everything. If they are relying on the inverter for power then they probably don’t have shore power which would power both hot legs of the system.

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