October 9, 2026 · 3 min read
What the converter and inverter actually do
The converter takes 120-volt shore power or generator power and turns it into 12-volt DC power. It runs your 12-volt items while you are plugged in and also charges the house battery. If it fails, the battery slowly drains even though you are connected to power, and nothing warns you until the lights start to fade.
An inverter does the opposite. It takes 12-volt power from your batteries and turns it into 120-volt household power so you can use outlets while boondocking. Many newer RVs have a combined inverter/charger that does both jobs, which means a single fault can affect charging and your outlets at the same time.
Warning signs your 12-volt system is not charging
The most common sign is a house battery that goes flat while the RV is plugged in. Other clues include interior lights that dim or flicker, a furnace fan that runs slowly or will not start, a water pump that sounds weak, slide-outs or jacks that move sluggishly, and control panels that reset or show error codes.
If you have a voltmeter or a monitor panel, check the battery voltage while plugged in. A working charger normally pushes the reading up to somewhere around 13 to 14 volts. If it sits at the battery's resting voltage or keeps dropping while you are connected, the battery is not being charged.
Listen and smell too. Many converters have a cooling fan, so a fan that never runs, runs constantly, or rattles is worth noting. A loud buzz, a hot plastic smell or scorch marks near the power centre mean you should unplug and stop using the system until it is inspected.
Safe checks before you call a shop
Start with the simple things. Confirm the campground pedestal or house outlet actually has power, and check the breaker there. Inside the RV, look at the 120-volt breaker panel for a tripped breaker feeding the converter, and reset any GFCI outlets. Then check the 12-volt fuse panel for blown fuses, including any reverse polarity fuses on the converter itself.
Make sure the battery disconnect switch is on and look at the battery terminals for corrosion or loose cables. A bad battery can look exactly like a bad converter, because a battery that will not hold a charge drains quickly no matter how well it is being fed. If your battery is several seasons old or was stored discharged over an Alberta winter, it may be the real problem.
If you switched to lithium batteries, confirm your converter or inverter/charger has a charging setting suited to them. Also remember that many lithium batteries should not be charged below freezing unless they have built-in cold protection, which matters on shoulder season trips around Calgary and into the mountains. Stop there. Opening the converter or working inside the power centre involves 120-volt power and is best left to a technician.
When to bring it to Horton in Calgary
If the basics check out and your battery still is not charging, it is time for proper testing. At Horton RV Services we can check charger output, test the battery under load, trace wiring and connections, and confirm whether the converter, inverter, battery or something in between is at fault, so you are not replacing parts on a guess.
Electrical problems are easier to sort out before a trip than at a campsite with a dead battery. If you are getting ready for the season, or you noticed charging issues on your last outing, book in and we will track it down. If the fault followed a collision, flood or storm, we can also document the damage for an insurance claim.
Common questions
Can I still use my RV if the converter is not working?
For a short time, yes, as long as your battery has charge. The 12-volt items will run off the battery until it drains, but nothing will recharge it. Expect lights, the furnace fan and the water pump to quit once the battery runs down, so get it checked before relying on the RV.
How do I know if it is the battery or the converter?
Check battery voltage while plugged in. If it rises to around 13 to 14 volts, the charger is probably working and the battery may be failing to hold a charge. If the voltage stays low while you are connected, the converter, a fuse or the wiring is more likely. A load test on the battery confirms it either way.
Why do my outlets not work when I am off shore power?
Regular outlets only work off-grid if your RV has an inverter and it is switched on. If it does, check that it is turned on, that the batteries have enough charge, and that you are not overloading it with a high-draw appliance. If it still shuts off or will not start, have the inverter tested.