ServiceNomad RV · Knowledge
RV Fridge Only Works on Electric
When an RV refrigerator cools properly on electric mode but fails to cool on propane, the issue is isolated to the gas burner system or its associated controls. This is a common problem, especially if the refrigerator has been stored for months without use or if the RV has been towed over rough roads. Understanding the propane system's ignition sequence and common failure points helps you communicate effectively with a technician.
How Gas Mode Works
In gas mode, the refrigerator's control board opens a gas valve and energizes an igniter (either a spark electrode or glow-type igniter) to light a small propane burner at the base of the absorption cooling unit. The flame heats the boiler tube, driving the ammonia refrigerant through the cooling cycle. A flame sensor monitors the burner—if flame is detected, the gas valve stays open; if no flame is detected after several ignition attempts, the control board shuts down and may display a CHECK light. If gas mode isn't working, the burner isn't lighting, the flame isn't being detected, or gas isn't reaching the burner due to supply issues.
Ignition System Failures
The most common cause of gas-mode failure is a failed or misaligned igniter. Older refrigerators use a spark electrode that produces a visible spark to ignite the gas. The electrode can become carbon-fouled, corroded, or knocked out of position from road vibration. If the electrode gap is too wide or too narrow, ignition won't occur reliably. Newer refrigerators use a glow-bar or hot-surface igniter that glows red-hot to ignite the gas. These igniters can crack, develop high resistance, or fail electrically. A technician will test the igniter for proper operation—spark igniters should produce a strong blue spark, and glow igniters should glow visibly within seconds of power-on.
Burner Orifice and Gas Supply
Even with a functioning igniter, the burner won't light if gas isn't flowing. Common causes include a clogged burner orifice (often from insect nests—spiders love to build in burner tubes), a kinked or blocked gas line, low propane pressure (empty tank or failing regulator), or a failed gas valve on the refrigerator. A technician will verify gas supply by checking pressure at the refrigerator inlet (should be 11 inches water column) and testing the gas valve solenoid for proper operation (it should click audibly when energized). They'll also inspect and clean the burner orifice and tube, as even a small blockage can prevent ignition.
Flame Sensor and Detection Circuit
After ignition, the control board monitors a flame sensor (a metal probe positioned in the flame) to verify combustion. If the flame sensor is dirty, corroded, or improperly positioned, it won't detect the flame even if the burner is burning perfectly. The control board interprets this as 'no flame' and shuts off the gas valve after a few seconds. Cleaning the flame sensor with fine steel wool or emery cloth often restores function. The sensor must be positioned so the flame directly contacts it—if the flame is lazy, yellow, or blown to one side by wind, the sensor may not heat adequately. A baffle or improved venting can help stabilize the flame.
⚠️ Safety Notes
- If you smell propane near the refrigerator or inside the RV, immediately shut off the propane supply and ventilate the area before attempting diagnosis.
- Never use matches or lighters to check for gas flow at the burner—use a gas detector or have a technician perform this test safely.
💡 Prevention Tips
- Inspect and clean the refrigerator burner assembly annually, especially if the RV is stored outdoors where insects can access the vents.
- Test the refrigerator in gas mode before each trip to ensure it lights properly—don't wait until you're at camp without shore power.
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