An RV converter that's not charging the battery is most often caused by (1) a blown converter fuse or tripped breaker, (2) loose or corroded battery connections preventing charge from reaching the battery, (3) a deeply discharged or sulfated battery that the converter can no longer recover, or (4) a failed converter itself. A 5-minute multimeter test at the battery terminals will tell you which.
Most likely causes (in order of likelihood)
- Blown converter fuse or tripped breaker — always check first.
- Loose, corroded, or damaged battery connections.
- Deeply discharged or sulfated battery — most converters won't begin a charge cycle if voltage is below ~10.5V.
- Failed converter — internal component failure.
- Bad shore power connection — converter not receiving full AC voltage.
- Failed converter cooling fan causing thermal shutdown.
- Loose AC wiring to the converter.
Diagnostic steps (in order, free/cheap before expensive)
- With shore power plugged in and the RV powered, measure voltage directly at the battery terminals with a multimeter. You should read 13.2V-14.4V if the converter is charging. If you read battery resting voltage (12.0V-12.8V), the converter is not delivering charge.
- Check converter fuses and the AC breaker feeding the converter. Most converters have one or more 20-30A DC fuses on their output. Replace any blown fuse.
- Inspect battery terminals. Corrosion (the white/green crusty buildup) will block current flow even when everything else works. Clean terminals with a wire brush and apply terminal protectant.
- Verify shore power. Plug in a known-good appliance to confirm the pedestal is delivering full voltage. Check at the converter input if possible.
- Test battery health. A battery below 12.0V at rest may be deeply discharged or sulfated. Try charging with a portable smart charger — if it accepts a charge, the battery is OK and the converter is suspect. If it doesn't, the battery is dead.
- Listen for the converter cooling fan. If silent and the converter is warm, the fan may have failed causing thermal shutdown.
- If voltage at the battery is low, fuses are good, connections are clean, shore power is good, and the battery accepts a charge from another source — the converter has failed. Replacement is $150-$400 depending on amperage.
DIY vs. call a tech
All testing is DIY with a $20 multimeter. Converter replacement is intermediate DIY for anyone comfortable with 12V wiring and basic AC connections — most converters drop into the same physical space as the original.