Quick answer: A Suburban RV water heater not lighting almost always has one of three problems. Propane isn’t reaching the burner, the controls have less than 10.5 volts DC, or a safety device has shut the heater down. Check that the tank has water, purge air from the gas lines, check your battery, then reset the lockout.
Why won’t my Suburban RV water heater light?
Most no-light problems come down to three things. The burner has no propane, the controls have too little 12-volt power, or a safety device has shut the heater off. That safety device is either a DSI lockout or a tripped ECO (energy cut-off).
Run these three quick checks before anything else:
- Water: The tank is full of water.
- Propane: The tank valve is fully open and the air is purged from the lines.
- Power: The battery reads at least 10.5V and the fuses are good.
Suburban DSI (direct spark ignition) heaters try to light the burner. If it doesn’t light, the system tries two more times. After that, it goes into lockout and a red indicator light comes on, according to Suburban’s operation manual for the SW4D, SW6D, SW6DE, SW6DM and SW6DEM. A lockout is a symptom, not the cause. It tells you the heater tried three times and failed.
What symptom are you seeing?
Match your symptom below, then jump to the section that fits. The checks are listed in order from easiest to hardest.
| Symptom | Most likely cause | Where to start |
|---|---|---|
| No click and no flame | No 12V power or a bad igniter | 12-volt power section, then our guide on a Suburban igniter that isn’t clicking |
| Clicks but no flame | Air in the gas lines, no propane, or low voltage | Propane section, then 12-volt power section |
| Lights, then goes out | Flame sensing, electrode gap, low voltage under load, or low gas flow | “Why does it light and then go out?” |
| Red light on | DSI lockout after three failed tries | Reset section, then our Suburban DSI fault light guide |
| Works on electric, not on gas | A gas-side problem: propane, 12V controls, or ignition | Propane section, then 12-volt power section |
Why does my RV water heater work on electric but not on gas?
The electric element and the gas burner use separate parts. If you have hot water on electric, the tank is full of water. The problem is on the gas side. Check propane supply first, then 12-volt power to the controls, then ignition.
Is the tank full of water?
Never fire the heater with an empty tank. To check, pull open the lever on the pressure relief valve on the outside of the heater. If water flows out, the tank is full. If only air comes out, open a hot faucet inside the RV and let the tank fill until water runs steadily.
Then check the bypass valve. If it is still set to winterize, water goes around the heater instead of into it. Set it back to normal before you light anything.
Two warnings about water
- Dry firing: On pilot-model heaters, even a short run without a full tank can permanently open the high-limit switch in the thermostat assembly, per Camping World.
- Cold water into a hot tank: Adding cold water to a hot Suburban tank can crack its glass lining. If the bypass was in winterize mode while the heater ran, Camping World says to wait 60 to 120 minutes before refilling.
Is propane reaching the burner?
A heater that clicks but won’t light is often getting spark but no gas. Start with the basics:
- Confirm the propane tank or cylinder actually has gas in it.
- Open the container valve fully.
- Light a stove burner. If the stove won’t light either, the problem is your propane supply, not the water heater.
How do I get air out of my RV propane lines?
Air can get into the propane lines after you refill an ASME tank or swap a DOT cylinder. Lighting a stove burner and letting it run should purge most of the air, according to Camping World. Once the stove burns steadily, try the water heater again.
Be patient on the first start-up. Suburban’s manual notes that the first start-up may take several ignition cycles before all the air is purged from the gas lines. One lockout right after a refill is normal.
Check the lines, and stop if you smell gas
Look for kinked, crushed or damaged propane lines where you can see them. If you smell gas at any point, stop. Turn off the propane at the tank, don’t use any switches or flames, and follow the gas-safety steps in your heater’s manual.
Does the heater have enough 12-volt power?
Even a gas water heater needs 12-volt power. The circuit board, the igniter and the gas valve all run on it. Camping World notes that it takes at least 10.5 volts DC to hold open the coils on the gas valve. Low battery voltage is more common when dry camping.
Why weak voltage gives you a spark but no flame
A weak battery may still have enough power to make the igniter click. But when the gas valve tries to open at the same time, the voltage can drop below what the valve coils need. The result is a spark with no gas behind it, followed by lockout.
How to check 12-volt power
- Battery: Measure voltage at the battery with a multimeter. If it is low, charge it or plug into shore power, then try again.
- Fuses and breakers: Check the water heater fuse in your 12V panel and any related breakers. Blown fuses and tripped breakers can cut power to the controls.
- Wiring: Look for loose, corroded or damaged wires to the heater. Damaged wiring can cause a voltage drop even with a good battery.
How do you reset a Suburban water heater after lockout?
Suburban’s manual gives a simple reset for a DSI lockout. You use the water heater switch inside the RV. There is no separate button for this.
- Turn the water heater switch OFF.
- Wait at least five seconds.
- Turn the switch back ON.
- Listen for the clicks and watch the burner. The heater will try to light up to three times.
If you just refilled propane, repeat the reset a few times, because air may still be in the lines. If it keeps locking out after that, the reset isn’t the fix. Move on to the checks below. For what the red light can point to, see our Suburban DSI fault light guide.
Has the ECO or high-limit switch tripped?
The ECO (energy cut-off) is a safety switch that cuts power when the tank gets too hot. On SW6DE and SW6DEM models, Suburban’s manual says it trips above 180°F. A tripped ECO can stop the heater from working.
Where is the reset button on a Suburban RV water heater?
The lockout reset is just the ON/OFF switch inside the RV. The ECO is different. On SW6DE and SW6DEM models it has a manual reset button on the thermostat and ECO assembly, reached through the outside access door. The exact spot varies by model, so use the diagram in your model’s manual. Turn off power to the heater before you reach in.
The water must cool below 110°F before the manual reset button will push in. If it won’t stay in, give the tank more time to cool.
Decision rule: don’t keep resetting it
An ECO trips for a reason. Something let the water get too hot, such as a faulty thermostat or an overheating problem. If it trips again, stop resetting it. Camping World advises having an RV technician diagnose and reset a tripped ECO.
Why does it light and then go out?
If the burner lights for a few seconds and then shuts off, the heater usually can’t confirm the flame or can’t keep it going. Common causes include:
- Flame-sense problems: The board doesn’t detect the flame, so it shuts off the gas for safety.
- Electrode gap: The spark electrode gap has opened up or moved out of position.
- Low voltage under load: The battery holds up at first, then sags while the gas valve is open.
- Low gas flow: Air in the lines, a nearly empty tank, or a supply problem starves the flame.
What color should the flame be?
A healthy flame is mostly blue. A lazy, yellow flame suggests blocked air or poor gas flow. Either one can make the flame unstable and harder for the heater to sense.
What you can safely check yourself
With the heater switched off and fully cool, open the outside access door. Look into the burner area for debris, spider webs, insect nests or other blockages. Clear anything loose you can reach without taking parts apart.
Leave the gas valve, propane pressure and circuit board to a technician. These parts control gas flow, and mistakes can create a safety hazard.
When should you call an RV technician?
Stop troubleshooting and call a qualified RV technician if any of these apply:
- You smell propane.
- The ECO keeps tripping.
- The heater still locks out after you have confirmed water, propane and at least 10.5V.
- The gas valve needs testing.
- The LP regulator pressure needs checking.
Keep your heater’s model and serial number handy. You can find manuals and support from Suburban’s parent company, Airxcel, at RVComfort.com or by calling 423-775-2131. Always follow the manual for your exact model, because steps and reset locations can differ.
Frequently Asked Questions
Why does my Suburban water heater click but not light?
A Suburban water heater that clicks but won’t light is usually making a spark with no gas behind it. Common causes are air in the propane lines, an empty or closed tank, or low battery voltage. A weak battery can still power the igniter but drop below 10.5 volts when the gas valve tries to open.
What does the red light on a Suburban water heater mean?
The red light means the DSI system has gone into lockout. The heater tried to light the burner three times and failed. The light is a symptom, not the cause. Reset it by turning the switch off for at least five seconds, then find and fix the propane, power or ignition problem.
Is it normal for a Suburban water heater to lock out after a propane refill?
Yes, one lockout right after a refill is normal. Air can get into the lines when you refill an ASME tank or swap a DOT cylinder. Suburban’s manual notes the first start-up may take several ignition cycles. Run a stove burner to purge the air, then reset the heater a few times.
How many volts does a Suburban RV water heater need?
The controls need at least 10.5 volts DC to hold the gas valve coils open. The circuit board, igniter and gas valve all run on 12-volt power, even in gas mode. Check the battery with a multimeter, then check the water heater fuse, breakers and wiring for a voltage drop.
Can I light my RV water heater with no water in the tank?
No. Never fire the heater with an empty tank. On pilot-model heaters, even a short dry run can permanently open the high-limit switch. To check, pull the pressure relief valve lever. If only air comes out, open a hot faucet inside the RV and let the tank fill until water runs steadily.
What temperature does the Suburban water heater ECO trip at?
On Suburban SW6DE and SW6DEM models, the ECO trips when the water goes above 180°F. The water must cool below 110°F before the manual reset button will push in. If the ECO trips again after a reset, stop resetting it and have an RV technician find the cause.
