ServiceNomad RV · Knowledge
RV AC Not Turning On
A completely dead AC unit—no fan, no hum, nothing—is almost always an electrical supply or control issue. RV air conditioners require two types of power: 120V AC (like a house outlet) to run the motor, and 12V DC (battery power) to run the thermostat and control board.
Check 120V AC Power Source
First, ensure your RV has 120V power. Is the microwave display on? If not, check your shore power pedestal breaker. It’s common for the 30-amp breaker at the pole to trip. If you are running on a generator, ensure the breakers ON THE GENERATOR ITSELF are not flipped off. Check your RV's main breaker panel inside. Locate the breaker labeled 'A/C' or 'Air Cond'. Flip it firmly OFF and then back ON. Sometimes a tripped breaker doesn't look tripped.
Thermostat and 12V Control
Your wall thermostat runs on 12V DC battery power (or internal AA batteries). If your RV house batteries are dead, the thermostat won't work, and it can't tell the AC to turn on. If the thermostat display is blank, replace its batteries or check your RV's 12V fuse panel for a blown fuse labeled 'Furnace/Thermostat'.
Control Board Fuse
There is often a hidden control box up inside the ceiling assembly (return air vent). Some models have a small glass fuse on this board. If that fuse blows, the unit is dead. This usually requires a technician to access, as it involves working near high-voltage wiring.
⚠️ Safety Notes
- Never work on AC wiring while plugged into shore power.
- Capacitors can hold a charge even when power is off.
Can't fix it yourself?
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