So here's what's got me scratching my head... My Class A has this red fault light glaring at me from the power panel, but it's not a total blackout situation. AC is running fine (thank goodness!), but my fridge, microwave, and some outlets decided to take a vacation.
I already tried the usual suspects - reset every GFCI I could find inside and messed with the main power cord panel outside where shore power comes in. Still got that annoying red light mocking me.
This partial power thing is driving me nuts. What should I be checking next to get everything back online?
Red fault light with partial power loss often indicates tripped breaker, one leg of 50 amp service failed, or GFCI trip. Check all breakers in main panel and find hidden GFCI outlets. May indicate transfer switch issue if breakers are fine.
Your PWR Panel Red Fault Light indicates a 12V DC system problem that's preventing your inverter from powering your 120V outlets, refrigerator, and microwave. Since your AC still works (it runs directly off shore power), but your inverter-fed circuits don't, you likely have a blown fuse or breaker in your 12V system that controls the inverter operation. The fact that resetting GFCIs didn't help confirms this isn't a ground fault issue but rather a DC power supply problem to your inverter system.
The red fault light on your power panel is specifically designed to alert you when there's a problem with the 12V DC system that feeds your inverter. Your AC works because it connects directly to shore power through the transfer switch, bypassing the inverter entirely. However, your refrigerator (when in AC mode), microwave, and outlets rely on the inverter to convert 12V DC battery power to 120V AC power when not on shore power. When on shore power, these typically run directly through the transfer switch, bypassing the inverter.
Common causes include a blown 12V fuse that feeds the inverter control circuits, a tripped DC breaker, loose battery connections causing voltage drop, or the inverter itself going into protection mode due to overload or overheating. The inverter needs steady 12V power to operate its control circuits even when you're plugged into shore power. Without this DC control power, the inverter can't function properly, leaving those circuits dead.
Another possibility is that your converter/charger has failed. Since the converter/charger is what charges your batteries, its failure would prevent proper battery charging and maintaining the 12V system voltage needed for inverter operation. This creates a cascading failure where low battery voltage triggers the inverter's low-voltage protection, shutting down those circuits you mentioned.
For this diagnosis and repair, gather a digital multimeter to check 12V system voltage and continuity, a basic set of screwdrivers and wrenches for accessing electrical panels, a flashlight or headlamp for working in dark compartments, and potentially replacement fuses (typically 50-80+ amp ANL or MEGA fuses for inverter circuits, though specific types vary - check manufacturer specs). You'll also want electrical contact cleaner and a wire brush for cleaning any corroded connections you discover.
Have your RV owner's manual handy to locate the specific DC fuse panel and identify which fuses control your inverter system. Some Class A RVs have the DC fuses in the same panel as the AC breakers, while others have a separate 12V fuse block near the batteries or in a basement compartment.
Before beginning any electrical work, turn off the main DC disconnect switch for safety. Start by checking your battery voltage at the batteries themselves using your multimeter - you should see around 12.6V when not charging, or 13.6-14.4V when the converter is running (shore power must be connected to test converter operation). If voltage is below 12V, your batteries may be too discharged to run the inverter properly. Next, locate your DC fuse panel (often labeled and near your main electrical panel) and visually inspect all fuses, particularly any labeled "inverter," "converter," or "12V outlets."
Pull out each suspect fuse and check for continuity with your multimeter, or visually inspect blade fuses for a broken element. Pay special attention to higher-amp fuses (30-40 amp range) as these typically feed inverter systems. Replace any blown fuses with the exact same amperage rating. If fuses look good, check the main DC breaker that feeds your inverter - it may have tripped and need resetting.
If all fuses and breakers check out, examine your battery connections for corrosion or looseness. Clean corroded terminals with the wire brush and contact cleaner, then tighten connections snugly. Finally, check if your inverter has its own reset button or circuit breaker - many models have a red reset button on the unit itself that may need pressing after an overload condition.
After making any repairs, turn your power panel back on and check if the red fault light extinguishes and your outlets/appliances restore power. Test each circuit individually to ensure proper operation.
Call a professional RV technician if you find blown fuses that immediately blow again after replacement, as this indicates a short circuit that requires tracing and repair. Also seek professional help if your multimeter readings show proper 12V voltage everywhere but the inverter still won't operate - this could indicate internal inverter failure requiring replacement, which typically costs $300-800 plus labor.
If you discover severely corroded or melted wiring connections, stop your diagnosis immediately and call a pro, as this represents a fire hazard that needs expert attention. Additionally, if you're uncomfortable working with electrical systems or can't locate your DC fuse panel, it's better to have a qualified technician diagnose the issue rather than risk damaging expensive components through trial and error.
Help us improve this article by flagging technical issues or inaccuracies.
Was this guide helpful?
Try our free RV calculators and tools to help diagnose and plan your repairs.
Browse RV ToolsWeight calculator, electrical planner, propane estimator & more