RV OWNER’S FIELD GUIDE · APPLIANCES
Forced-Air Furnace Troubleshooting
Suburban and Atwood forced-air furnaces — the ducted heating system, not the water heater sharing the same brand name.
Blower Runs but No Heat
This isolates the fault to ignition, not the blower motor. Check LP supply pressure, the sail switch (which confirms airflow before allowing ignition — a common failure point), and the igniter/electrode assembly for carbon buildup or a cracked ceramic.
Furnace Won’t Start at All
Check 12V supply first — furnace ignition boards are voltage-sensitive and won’t attempt ignition below a threshold the thermostat display may not warn you about. After that, check the thermostat’s own battery or wiring and the door/limit switch, which shuts the unit down if a service door is ajar.
Weak or Uneven Heat Through the Ducts
Usually a duct or register obstruction rather than a furnace fault — check that nothing is blocking floor registers, and that the return air path to the furnace itself is clear. A furnace short-cycling (starting and stopping rapidly) instead points to the sail switch or a restricted exhaust, not the ductwork.