RV water heater not working on gas or electric: 11 checks in order

Common symptoms

• You open a hot faucet and only cold water comes out, on gas or electric.
• The heater works on propane but not on electric, or the other way around.
• A red light on the inside switch panel comes on a few seconds after you turn the heater on.
• A tankless heater goes out when you turn the faucet down.

Quick checks before anything else

• A hot faucet runs a steady stream with no sputtering air, so the heater is full.
• The bypass valves are set for normal use, not for winter storage.
• The propane tank has gas, its valve is open, and a stove burner lights.
• The gas switch or the electric switch (or both) is on.
• The water heater fuse on the 12V panel is good, and the battery reads about 12.6 volts.
• For electric heat, the RV has shore power and the water heater breaker is on.
• On a tankless unit, the hot faucet is open all the way.

What causes it?

• Bypass still in winter mode Water flows around the heater instead of through it, so you get cold water right away.
• No propane at the burner An empty tank, a closed valve, or air in the line after a refill makes the gas side lock out.
• No 12V power to the controls A blown fuse, a dead battery or a switch left off stops the gas side with no clicking at all.
• ECO tripped The ECO (energy cut-off) is a safety switch that cuts the heat when the water gets too hot.
• Burned-out electric element It works on gas but never on electric, often after the element ran in an empty tank.
• Too little flow on a tankless unit The burner only fires when enough hot water moves.

Step-by-step: getting your RV water heater working again

When your RV water heater is not working on gas or electric, we check water first, then gas, then power. A heater with no water in it can be damaged by the very fix you try.

1. Prove the tank is full Open a hot faucet and wait for a steady stream with no spitting air. If the heater sat unused for two weeks or more, first run the hot faucet at the kitchen sink for several minutes with no flame nearby. Suburban and Dometic both warn that flammable hydrogen gas can build up in an unused heater.

   

2. Set the bypass valves for normal use A bypass kit routes water around the heater for winterizing. Truma’s plumbing diagram shows the usual layout: a valve on the cold inlet, a valve on the hot outlet, and a bypass valve between them. For normal use, the inlet and outlet valves are open and the bypass is closed. Some RVs use one combined valve; check your RV’s manual. If the bypass was open, the tank may be empty, so repeat step 1 before you turn on any heat.
3. Confirm propane at the stove Check the tank level, open the tank valve all the way, and light a stove burner. If the stove lights but the water heater does not, and you just refilled or swapped tanks, there may be air in the line. Suburban says the first start-up can take several ignition tries to purge it. If the heater never clicks or never lights, see RV water heater igniter not clicking or won’t light on gas.
4. Check both switches Gas and electric usually have separate switches. On a Suburban with an electric element, the electric switch is behind the outside door in the lower left corner of the control housing. Dometic XT models have a gas switch and an electric switch. Girard and Furrion tankless units also have a power switch inside the outside compartment.
5. Check 12V power and the fuses The gas side needs 12V DC for its control board, even though it burns propane. Replace a blown water heater fuse on the 12V panel with one of the same rating. Dometic heaters also have a 2 amp fuse on the circuit board, and Dometic says never to use one larger than 3 amps. If a new fuse blows again, look for a short first. Never power the heater from a battery charger alone: Dometic, Girard and Truma all say not to, even for testing.

   

6. Reset a lockout or ECO once On a Suburban, clear a gas lockout by turning the switch off, waiting 5 seconds, and turning it on. Its red ECO button trips above 180°F and resets only once the water is below 110°F. On a Dometic XT, the red lamp means the gas side locked out after three tries. Fix the cause, then turn the switch off and on. After an overheat, Dometic says to leave it off at least 30 seconds. If the ECO trips again, Dometic points to a failed thermostat or one not touching the tank, which is a tech job.
7. Look for nests in the burner tube With the heater off and cool, open the outside door and look at the burner tube and vent. Dometic warns that spiders and mud wasps build nests in the burner tube, causing poor combustion and delayed ignition. A soft, lazy or very yellow flame is the sign. Suburban says that if you see soot anywhere on the heater, shut it down and call a qualified service person.
8. Works on gas but not on electric: check 120V First make sure 120V reaches the RV. If the wall outlets are dead too, see RV has no power when plugged in. Then check the water heater breaker and the electric switch. Suburban E models such as the SW6DE have a high-limit reset for the element too, which trips above 180°F and resets below 110°F. On a Dometic XT, reset the electric side by turning its switch off, then on.
9. Suspect a burned-out element If power, breaker, switch and reset are all good, the element has likely failed. Suburban calls switching on an electric heater before it is filled “by far the most common trouble” and says even brief operation without water burns out the element. Replacing it means draining the tank and working on 120V wiring, so turn the breaker off first or hand it to a tech. Dometic warns against aftermarket heating element add-ons, which can overheat the tank.
10. Tankless: give it enough flow Girard and Furrion ask for at least 0.8 gallons per minute (gpm) for each hot faucet, Suburban’s ST-42 and ST-60 need 0.7 gpm, and Truma’s AquaGo starts at about 0.4 gpm. Open the hot tap fully until hot water arrives. Suburban says not to use a shower head’s flow-stop button, because cutting the flow shuts the heater down. Girard and Furrion have a filter screen at the cold inlet, and Truma says to clean its inlet filter at least once a year. If the pump gives a weak or pulsing flow, see RV water pump runs but no water comes out.
11. Read the code if the panel shows one Girard and Furrion show codes such as E1 or En on the wall panel, and Truma’s AquaGo blinks a pattern on a red LED behind the outside door. Look yours up in our Girard and Furrion code list before you buy parts. Suburban tank heaters show no codes, and Dometic tank heaters only light a red lamp.

Suburban, Atwood and tankless: differences by model

Suburban SW6D family. These tank heaters show no codes. The burner tries three times, with a 15-second purge (a pause that lets old gas clear) before each spark on three-try systems, then locks out.

Atwood, now Dometic XT. Gas and electric can run together for faster heating, which hides a gas lockout: Dometic says the red lamp stays off while the electric side runs. If recovery seems slow, turn the electric switch off. If the lamp then lights, the gas side has locked out. For no heat at all, Dometic also lists supply voltage over 14 volts and a melted thermal cutoff from a blocked flue tube.

Tankless (Girard, Furrion, Truma). Most problems come down to flow, propane and 12V. Girard and Furrion shut off after 20 minutes of running and show En, and Truma shuts off below 10 volts or above 16.4 volts. How each part works is in our RV water heater repair guide.

When to call an RV tech

• The ECO trips again after a reset.
• A new fuse blows right away, which means a short in the wiring.
• The element needs replacing and you are not comfortable draining the tank and working on 120V.
• Propane and 12V are good and the gas side still locks out. Suburban tells owners not to try to repair the gas valve.
• A Dometic thermal cutoff has melted. The flue blockage must be cleared and the cutoff replaced.
• You see soot, a yellow flame, or water leaking from the tank body.

If the only problem is water dripping from the valve on the front of the heater, read why your RV water heater relief valve is leaking. Some dripping is normal.

Common questions