Why Your RV Trips GFCI at Home But Not Campground: Complete Troubleshooting Guide

Short Answer

Since your motorhome trips house GFCIs even with the main breaker off but works fine on 30A campground pedestals and your generator, you likely have a ground fault in the shore power cord itself or the transfer switch/inlet connection. The fact that it happens with all your house GFCI outlets and even with the MH main breaker off points to a fault in the power cord or connection between the plug and your motorhome's electrical panel, not in your RV's internal wiring.

Understanding the Problem

Your situation is actually quite common and reveals an important distinction between campground pedestals and residential GFCI outlets. Most campground 30A pedestals don't have GFCI protection - they rely on your RV's internal GFCI outlets for protection. However, your house outlets are GFCI-protected and are detecting a ground fault that campground pedestals can't see.

Since you've confirmed the problem persists even with your MH's main breaker off, the issue isn't in your coach's 120V wiring system. Instead, there's likely a ground fault between your shore power inlet and the main panel. This could be in the shore power cord, the inlet connection, or the transfer switch if your motorhome has one. The adapters you tried aren't the issue since multiple GFCI outlets react the same way.

Common causes of ground faults in shore power systems include moisture intrusion, damaged insulation in the cord, or corrosion at connection points. Even a small amount of current leaking from hot or neutral to ground will trip a sensitive residential GFCI, which is designed to trip at 4-6 milliamps of ground fault current per NEC standards for Class A GFCIs used for personnel protection.

What You'll Need

For diagnosis, you'll need a digital multimeter capable of measuring resistance (ohms), and ideally a megohmmeter or insulation tester if you can borrow or rent one. You'll also want basic electrical tools including wire strippers, electrical tape, and possibly dielectric grease for connections.

If you find damaged wiring, you may need replacement shore power cord (typically 25-50 feet of 10 AWG 3-conductor with ground cable, costing $150-300), new inlet receptacle ($30-80), or electrical connectors and wire nuts for junction repairs. For transfer switch issues, replacement parts can range from $50-200 depending on your system.

WARNING: Shore power electrical work carries serious electrocution risk due to high amperage 120V circuits. Safety equipment is crucial: ensure you have a non-contact voltage tester, work gloves, and safety glasses. Never work on electrical systems while connected to shore power, and always verify power is off before beginning work. Even with power disconnected, stored energy in capacitors can present shock hazards.

How to Fix It

Start by completely disconnecting your shore power cord from both the motorhome and house outlet. Using your multimeter set to resistance mode, test between each conductor and ground at both ends of the cord with the cord completely disconnected from the RV. You should see infinite resistance (open circuit) between hot-to-ground and neutral-to-ground when nothing is connected. Hot-to-neutral should show infinite resistance when the cord is disconnected from all loads. Any measurable resistance indicates insulation breakdown.

Next, inspect your shore power inlet where the cord connects to your motorhome. Look for corrosion, burnt connections, or moisture damage. Remove the inlet cover and check all wire connections for tightness and signs of arcing or overheating. Clean any corrosion with electrical contact cleaner and ensure connections are tight.

If your motorhome has an automatic transfer switch, this is another common failure point. With shore power disconnected, check the transfer switch connections and look for any signs of moisture or damage. Some transfer switches have known issues with internal ground faults that only show up under certain conditions.

Test your findings by reconnecting the shore power cord to your motorhome (with main breaker still off) and carefully plug into a house GFCI outlet. If it still trips immediately, the fault is definitely in the cord or inlet connection. If it doesn't trip with the main breaker off, turn the main breaker on - if it then trips, the issue is in your electrical panel or transfer switch area.

Leave It to the Experts

If your multimeter testing reveals ground faults but you can't locate the specific problem area, it's time to call an RV electrical technician. Shore power systems carry significant current and improper repairs can create fire hazards or electrocution risks. Many RV dealerships and mobile RV repair services have the proper test equipment to quickly isolate ground faults.

Professional diagnosis typically costs $100-150 but can save you from expensive trial-and-error parts replacement. Technicians have specialized insulation testers that can pinpoint exactly where in your system the ground fault occurs, whether it's in the cord, connections, or transfer switch components.

Additionally, if the problem turns out to be in your home's electrical system rather than the RV (though less likely given your symptoms), you'll need a licensed electrician to address house wiring issues. Some insurance policies require professional electrical work for coverage, so check your policy before attempting major repairs.