RV furnace clicking but not igniting: causes and fixes

Common symptoms

• The fan runs and you hear fast ticking for several seconds, but no flame.
• Ticking, a quiet gap, more ticking, three rounds in all, then it gives up.
• The burner lights with a soft whoosh, then goes out a few seconds later.
• The fan runs, but you never hear any ticking.
• It lights on some tries and fails on others.
• The stove lights fine, but the furnace will not.

Quick checks before anything else

• A stove burner lights and holds a steady blue flame.
• The tank valve is fully open and the tank is not near empty.
• If you just refilled or swapped tanks, run a stove burner for a minute before you try the furnace.
• Battery voltage stays above 10.5 volts while the furnace fan runs.
• The air intake on the outside furnace vent is free of nests and snow.
• You reset the furnace once and listened to one full try.

Step-by-step: finding where ignition fails

When an RV furnace is not igniting or not lighting, the fan and the thermostat are already doing their job. The fault sits somewhere between “airflow proved” and “flame proved.” These steps find which part of that short window is failing.

1. Time one full try Reset the furnace and time one try. On a Suburban, the blower starts, the sail switch closes, and about 15 seconds of purge follow. Then the board opens the gas valve and sparks for about 7 seconds while it looks for flame. With no flame, it purges again and tries again. After three failed tries, it closes the gas valve and locks out. Atwood says to allow 30 seconds after the blower starts for the burner to light. Write down what you got: no ticking, ticking with no flame, or flame that dies.
2. Purge air from the gas line After a refill, a tank swap or long storage, the line can hold air. The furnace only sparks for a few seconds per try, so it can lock out before propane reaches the burner. Light a stove burner and let it run until the flame is steady, then reset the furnace. If it still will not light, do not keep cycling it: Atwood says that after three attempts with no ignition you should shut it down and call a service tech.
3. Check voltage while it tries to light The spark, the gas valve and the blower all run on 12V DC. Measure at the battery during a try. Suburban lists 10.5 volts as the minimum, and its fan control boards go into standby below 9.5 volts. Low voltage also slows the blower, and Suburban’s sail switch needs about 75% of normal blower speed to close. Then plug into shore power or run the generator and try again. If it lights now, the battery is the problem. See our RV battery and converter guide. Never run the furnace from a battery charger alone: Suburban warns some chargers put out more than 14.5 volts, which can damage the board.
4. No ticking at all: check the go-ahead circuit If the igniter is not clicking at all, the board has not been cleared to spark. It will not spark until the sail switch (the airflow paddle switch) and the limit switch (the overheat switch) both report OK. Suburban’s first check for “electrode not sparking” is voltage at the board after the blower reaches full speed, then continuity through those two switches. If the fan runs about 30 seconds and stops, that points to the sail switch, which we cover in RV furnace not working: 12 checks.
5. No ticking, switches OK: the electrode and its wire The electrode is a metal rod in a ceramic insulator that sits over the burner and makes the spark. With power and gas off, Suburban’s order is: check the wire connections at both ends, check the wire for continuity and replace it if open, then check the gap. The spark gap between the electrode and its ground should be 1/8 inch. Next, look for cracks in the electrode or carbon on its tip. If all of that checks out, Suburban says to replace the board, which is not field repairable.
6. Ticking but no gas: the gas valve If you hear the spark but the burner never lights, check whether the board sends 12V to the gas valve during the try. Suburban’s rule is simple. Voltage at the valve but no gas means a bad valve. No voltage means checking the wires and plug between board and valve, and if those are good, the board. Replacing a gas valve ends with a leak test, so we leave that to a tech.
7. Ticking, gas flowing, still no flame: pressure and burner Gas pressure is read with a manometer, a gauge that measures low gas pressure in inches of water column (WC). Suburban specifies 11 to 14 inches WC at the furnace and says the pressure should drop no more than 1/2 inch when the furnace starts. A bigger drop points to a bad regulator, a restricted or pinched line, or moisture. Atwood’s manuals call for 10 to 13 inches WC with all appliances running, read at a 1/8-inch test port. If pressure is good, Suburban says to look for a blocked burner orifice or burner and to check that the electrode sits about 1/4 inch above the burner slots.
8. Lights, then goes out in seconds: flame sensing Once the burner lights, the board must see the flame or it shuts the gas off. On many Suburban models it senses flame through the spark electrode, and others use a separate flame sensor. Suburban’s checks: the sensor sits in the inner blue cone of the flame, about 1/4 to 5/16 inch above the burner, with no carbon on it and tight wires at both ends. The flame itself should be hard blue. A tech can measure flame current with a microamp meter (a microamp is a millionth of an amp). Suburban wants at least 7 microamps within 7 seconds of lighting, and if that is good but it still drops out, the board is at fault.
9. Lights some tries, fails others Suburban blames occasional lockouts on gas pressure that dips when the furnace calls for heat (a weak tank regulator, a kinked line, or moisture), airflow that does not close the sail switch every time, or a dirty electrode and burner. To test the gas side, a tech can run the furnace from a separate upright tank and regulator, as Suburban’s manual describes. If it works that way, the RV’s gas system is at fault. Atwood’s owner manual says to shut the furnace down and call for service if it cycles erratically or is slow to light.

Suburban vs Atwood (Dometic) furnaces

Suburban. The service manual spells out electrode setup. The spark gap is 1/8 inch. On NT models the electrode sits 3/16 inch over the burner ports. Where there is a separate flame sensor, its gap to ground should be about twice the spark gap, 1/4 inch on park models. Sparking to the sensor damages the board. After the third failed try, fan control boards run the blower 3 more minutes and then stop.

Atwood (Dometic Hydroflame). Allow 30 seconds for the burner to light, and stop after three failed attempts. The board LED gives two codes that matter here. Two flashes with a 3-second pause is a flame sense fault, a “hard” lockout that waits for you to reset the thermostat or the furnace power switch. Three flashes is an ignition lockout, a “soft” lockout that the board retries on its own after one hour. The Atwood manuals we read do not list electrode gaps, so check your model’s service information or have a tech set it.

How the parts fit together is in our RV furnace repair guide.

When to call an RV tech

• The gas valve needs testing or replacing. Any gas fitting you open needs a leak test afterward.
• Gas pressure needs checking and you do not own a manometer.
• The electrode needs regapping and you cannot reach it without pulling the furnace.
• The board is the last suspect. Suburban boards are not field repairable.
• Flame current needs measuring.
• The burner is slow to light (delayed ignition), or you smell gas.

Common questions