Troubleshooting guide
Dometic Single Zone LCD auto fan speed cycling
Dometic Single Zone LCD thermostat instructions say Auto fan varies by the difference between setpoint and room temperature: the fan runs HIGH when the difference is greater than 5 F, LOW when it is less than 4 F, and cycles with the thermostat.
Use this atlas to identify likely meaning and prepare for service. Shut off power, LP gas, fuel, or water when a listed appliance condition involves flame, gas smell, exhaust, generator shutdown, high temperature, moving jacks/slides, refrigerant, 120 VAC, control boards, repeated ignition failure, or a persistent lockout. Call the appliance maker, RV dealer, or a qualified RV technician for repair.
Owner-safe checklist
- Record selected mode, setpoint, room temperature, and whether Fan shows Lo, Hi, or Au.
- Treat normal Auto fan speed changes as expected when room temperature approaches the setpoint.
- Select Lo or Hi from normal fan controls only if continuous fan operation is desired.
- Call qualified RV HVAC service if the display mode changes but fan behavior never matches the thermostat selection.