RV water heater not heating: The troubleshooting guide
When an RV water heater stops heating, the unit is usually not dead. The usual culprits are small: a flipped switch, a bypass valve still in winter mode, air in the propane line, or a safety reset that tripped and needs a press. The heater runs on two separate systems sharing one tank, propane and 120-volt electric, and they fail independently, so deciding which side is dead halves the search before any tool comes out.
By OriginRV. Last updated on Oct 2, 2026.
If the furnace also stopped working on gas, the shared part is the propane system rather than either appliance. See Two appliances stopped at once for why the two largest gas consumers fail first.
Start here: Match your heater to its fault
No hot water at all. It could be either side. Do the tank and valve checks first, they are free, then test each heat source in turn.
Works on propane, not electric. The fault is almost always electric-side: the element, a switch, or 120-volt power. The two systems share only the tank, so this split narrows the search fast.
Works on electric, not propane. The fault is almost always propane-side: no gas, air in the line, a dirty burner, or a safety lockout.
Warm but never hot. Usually a bypass valve left partially open, or cold water mixing into the hot line.
What is inside one
Almost every fault on this page sits in one of six parts, and a picture of them is worth more than the list.
The free checks: Tank, valves, and switches
Is the tank actually full?
If the RV was winterized and the drain plug or anode was left out, the tank is empty, and an empty tank burns out the electric element in seconds. Dometic's own manual warns that a dry element can burn out and void its warranty. A hot faucet will not tell you the truth here: if the bypass valves are still in winter mode, cold water crosses into the hot line and runs perfectly steady while the tank behind it is dry. So check the bypass setting first, then confirm the tank itself from the tank rather than the plumbing, by lifting the lever on the temperature and pressure relief valve on the heater's exterior face and letting water escape. Do that on a heater that has been off long enough to be cool: that lever discharges near-boiling water and steam from the face your hand is at, which is exactly why opening it is a safety test rather than routine maintenance. That is the one check that comes from the tank rather than from the plumbing around it.
Is the bypass still in winter mode?
If the RV was winterized, the bypass valves may still be set to route water around the heater. In that mode the heater never fills and you get cold water even though everything runs. On the common three-valve setup, two valves on the water lines and one on the bypass loop, normal operation is the two line valves open and the center bypass valve closed. If they are set the other way, flip them and give the heater time to fill.
Are the outside shower faucets off?
An outdoor shower with both faucets open can let cold water cross into the hot line and dilute the heat. Close them fully, both handles, then re-test.
Check both switches, including the hidden one
Many RV water heaters have an on-off rocker switch behind the exterior access door, on the face of the unit, separate from the indoor switch. It is easy to miss and a common reason a heater suddenly stops. Check the indoor switch and the one behind the access door before anything else.
The ECO reset: The fix you check before parts
Behind the same exterior access panel sits the emergency cutoff, or ECO, a high-limit safety switch that trips at about 180 degrees. It exists to shut the heat off when the thermostat fails closed and lets the water temperature climb unchecked. On a Suburban gas-electric unit there are two of them, one for the 120-volt element and one on the 12-volt side that feeds the gas valve, so a trip can kill either side or both. When one trips it stays tripped until somebody resets it, which is why a heater can simply stop working one day with no other symptom.
The temperatures are published, and they differ by brand and by heat source, which is why the reset behaves inconsistently from one RV to the next. Suburban states that a temperature above 180°F trips a manual reset on both the gas burner and the electric element, and that the reset will not hold until the water is back below 110°F. Atwood and Dometic put the gas side ECO at above 180°F, the electric side at above 170°F, and they fit a separate one-shot thermal cut-off that opens at 190°F when the flue or burner is blocked. That last one is a fuse, not a switch: it does not reset, it gets replaced. Dometic describes the consequence directly, that if the thermostat fails the ECO "will also lockout the Water Heater and a reset will be required."
Most units have a small reset button, often red, under the exterior access panel or on the thermostat assembly. Press and release it, and if the ECO was the problem, the heat comes back. The reset will not hold while the tank is hot: Suburban's manual puts the limit at about 110 degrees on its own units, so a Suburban button that refuses to click on a warm tank is behaving correctly, not failing. The figure is Suburban's, and the limits differ by brand. If it trips again right away once the water is cool, the real problem is upstream, usually a failed thermostat or heavy sediment, and the reset is a diagnostic result rather than a repair.
If it will not light on propane
Propane on and not empty? Open the tank valve fully. If the tank is low or just refilled, air in the line can stop ignition. A common trick: light a stove burner for a moment to bleed trapped air from the lines, then try the heater.
If it sparks and does not light, check the electrode gap before anything else. All three makers publish the same figure: Suburban and Atwood both specify 1/8 inch, and Dometic writes it as "0.125 in. (0.3175 cm)". A gap widened by heat, or a porcelain cracked by a knock, produces a spark that looks healthy in the dark and will not reliably light the burner. The manuals also tell you to clean carbon from the electrode while you are in there.
12-volt control power. The propane side runs on 12-volt DC for the ignition board, the spark, and the gas valve. A blown fuse kills propane ignition even while electric still works. Check the furnace and water heater fuse.
Can you hear the igniter clicking? If it clicks but no flame catches, the burner tube is likely dirty or blocked. If there is no click at all, suspect power, a fuse, or the board. If it clicks for a few seconds and then stops, that is a safety lockout: the unit did not detect a flame and is protecting itself. Turn the heater off for at least 30 seconds, then on again to reset it.
The flame color tells the story. When it runs, the flame should be a steady blue. A yellow or flickering flame means incomplete combustion, usually a dirty burner or a spider nest in the tube. Cleaning the burner tube is a routine owner job.
Why the flame color matters that much. Incomplete combustion produces carbon monoxide, and a water heater vents through the wall of the space you sleep in. A burner that is sooting, or a flue blocked by a nest or debris, sends that exhaust out beside whatever window or slideout is open. If you smell gas, shut it off at the tank, ventilate, and do not touch electrical switches or use a phone inside before you leave. If you find soot, stop using the propane side until somebody has looked at the flue.
If it will not heat on electric
120-volt power. Check the breaker and confirm you are on shore power or generator. No 120 volts, no heat.
Both switches on, and the ECO reset done. The indoor switch, the rocker behind the access door, and a reset high-limit covered all three quick fixes above.
The heating element. If power is present and the thermostat reads fine but the water stays cold, the element is the usual suspect. A dry-fired element, one that ran on an empty tank, can show telltale signs: a bulged or split sheath, blistering, or chalky white residue. Often it shows none of them, so a clean-looking sheath is not a pass: the element that ran dry frequently fails only on the continuity test below. It can be tested with a multimeter for continuity through the element and no continuity to the tank, and replaced for a modest part cost. When one element fails, replace it with the maker's own part. The maker's own part is the safe choice for the same reason the makers give about anodes: an aftermarket element can differ from the one the unit was built and approved around, and a maker is entitled to treat a part it did not supply as outside what it supports.
Gas works but electric does not almost always means the electric element or its 120-volt supply. The two systems share only the tank, so this split narrows it to the element, its wiring, and the electric-side thermostat.
Suburban vs Atwood: The two brands behave differently
The brand is on the heater's own data plate. On a unit whose label is gone, the anode is the tell, because the two are built differently: a Suburban drain fitting unscrews to reveal a sacrificial rod behind it, and an Atwood or Dometic has a plain drain plug with no rod at all. Which brand you have decides which parts exist and how the heater can fail. Suburban water heaters use a steel tank with a sacrificial anode rod. The rod protects the tank by corroding in its place, and it must be replaced as it wears, because an ignored anode leaves the steel tank exposed and the tank eventually corrodes. The anode screws into the tank and is a common leak point when cross-threaded or over-tightened, so install it cleanly with the correct tape. Atwood and Dometic heaters use an aluminum tank and a simple nylon drain plug, with no anode rod to maintain. The nylon plug can crack or wear over time, and these tanks take no anode rod: the tank is aluminium by design, so it drains through a plug rather than protecting itself with a sacrificial rod.
The two brands also differ in control layout. Suburban gas-electric models often carry two separate thermostats, one for the propane side and one for the electric side. That is why a Suburban can work on one heat source and fail on the other, and why it can overheat if the electric thermostat fails closed. Atwood units use a different thermostat and ECO arrangement. Knowing whether you have a Suburban or an Atwood tells the technician, or you, what parts to test and where the reset button lives.
Two things the makers say that are worth having exactly. Suburban publishes the interval twice and does not quite agree with itself: its operation manual says the anode "will deteriorate and because of this, we recommend it be replaced yearly", while its service manual gives a consumption test instead, recommending replacement "when consumption or weight loss is greater than 75%". The yearly one is the simpler of the two to follow, and it is the one to use if you are not going to weigh the rod, which is the only way to apply the other. Suburban also states plainly that "operating the Water Heater without the Anode voids Suburban's Limited Warranty". Read that as what it says: the rod is not an accessory, the warranty turns on it being fitted, and refitting one restores the protection the tank was missing rather than the season that has already passed. What it does to a claim for that season is a question only the maker can answer. And on the other side, adding an anode to an Atwood or Dometic tank is not merely unnecessary: Dometic writes that "replacing the Dometic drain plug with an Anode Rod will damage the coupling with cathodic action and product damage will result." That is the one to remember, because putting an anode in an aluminium tank is a common and well-meant mistake.
Overheating or lukewarm water
Overheating or the heater will not shut off. Usually a thermostat stuck closed, a build-up of sediment at the bottom of the tank, or the ECO not doing its job. The thermostat is set to open around 130 degrees and shut the element off, which is where Suburban sets it, and Atwood's manual gives 140 degrees for its own units; if it fails closed, the water keeps climbing until the ECO trip at roughly 180 degrees catches it. Heavy sediment at the tank bottom also traps heat and can trip the ECO, which is why flushing the tank is part of the fix. An anode that is fully consumed leaves the tank unprotected against corrosion, another reason to replace it when it is worn.
Warm but not hot. Usually a bypass valve partially open, a mix valve added in line, or cold water crossing in. A single-handle faucet left in the middle can pull from both lines at once.
Strange smells or soot. Heavy soot, or a flame that is not burning cleanly, means a combustion problem: stop using the propane side and have it looked at, because a combustion problem can become a safety problem. A rotten-egg smell is a different thing and usually not a fault at all: hydrogen sulfide comes out of the water supply reacting with the tank, and Dometic's manual covers flushing it out.
If you have a tankless heater
Tankless units fail differently, and they report what they think is wrong rather than leaving you to guess. Furrion's service manual documents the two codes owners see most. E1 is a flame sense fault during ignition, and the manual points first at fuel: confirm the gas valves are open, confirm there is fuel in the tank, and check the inlet pressure with the regulator. E5 is the air pressure switch, and it points at exhaust rather than gas: an obstruction in the exhaust, or high wind blowing directly at the exhaust, which the manual answers by moving or re-orienting the RV before restarting.
If a tankless unit runs but does not get hot, check the flow before the gas. These units need a minimum flow to fire at all, and Furrion publishes 0.32 gallons per minute as its figure. A single low-flow tap, a faucet aerator clogged with scale, or a restrictive shower head can sit below that, and the unit will sit there not heating while working correctly.
Winter is where they break. Furrion's instructions limit compressed air to 50 PSI when blowing the system out, and call for non-toxic antifreeze in the heater. The warning behind it is in the other makers' manuals too: water left in the heat exchanger freezes, expands, and splits the copper tube.
The pressure and temperature relief valve
This valve is a safety device and the manuals treat it as one. Suburban states it is designed to open if the water reaches 210°F or the pressure reaches 150 pounds. Atwood and Dometic state that it complies with ANSI Z21.22 and that the set pressure must not exceed 150 psi, with Dometic recommending a relief valve set to open at 100 to 125 psi on the cold inlet.
It is also meant to be operated. Dometic's instruction is that it be manually operated "at least once a year", and Furrion's is more specific: rotate the handle three to five times counterclockwise, and water from the drain hose proves it works. Suburban's version is to pull the handle and let water run until it stops, then release it and check that it snaps shut.
What you must not do is remove it or plug it, and every maker says so. Suburban prints "Do not remove or plug the relief valve." Dometic warns against operating it while the water is still hot. A dripping relief valve is usually doing its job, not failing; the documented cause is a missing air pocket in the tank, and the fix is to re-establish it rather than to plug the valve.
Owner-doable vs call a technician
You can reasonably replace the heating element, the thermostat, the ECO, the fuses, and the anode rod, and you can clean the burner. Tank level, bypass mode, both switches, the ECO reset and the element test are all within owner reach. You should hand off a tank leak, a failed gas valve, a bad circuit board, or anything inside the propane combustion chamber that you are not comfortable with. When a repair quote approaches the price of a new unit, ask what the labour is on its own, because most of that quote is the part and the access to reach it.
The rule that saves most owners
Work the free checks before you spend money: fill the tank, open the valves, find both switches, press the ECO reset, and test the element before replacing anything. The order is the diagnostic, not a sequence of guesses. One careful afternoon of these checks beats a replacement you did not need.
My heater works on propane but not electric. What does that tell me?
It isolates the fault to the electric side. Check the breaker, both switches, the ECO reset, and the 120-volt supply, then the heating element and its wiring. The propane system and the tank are fine, which is why the two-system split is the fastest diagnostic.
How do I test the RV water heater element with a multimeter?
Disconnect power first. Set the meter to ohms. Touch the probes to the two element terminals. A healthy element reads a low resistance and a dead one reads open, and the number to expect is arithmetic rather than a rule of thumb: ohms is volts squared over watts, so the 1,440 watt element this page quotes for a 120 volt unit should read about 10 ohms. A reading of 2 or 50 is not a healthy element with a tolerance, it is a different element or a different problem. Then touch one probe to a terminal and the other to the tank body, it should read open, and continuity there means the element has shorted and must be replaced. Match the wattage on the replacement to the original.
Why did my heater stop making hot water after winter storage?
Most common: the drain plug or anode was left out so the tank is empty, or the bypass valves were never returned to normal operation, or the electric element burned out because the heater ran dry. Check those three before anything else.
What is the ECO reset on an RV water heater?
The emergency cutoff is a high-limit safety switch that trips about 180 degrees. On a Suburban gas-electric unit there are two, one on the 120-volt element and one on the 12-volt side that feeds the gas valve, so a trip can kill either side or both. When it trips, that side goes dead until somebody resets it, often red and behind the exterior access panel, and the reset will not hold while the tank is hot: the water has to be below about 110 degrees. If it trips again once the water is cool, the thermostat or sediment is the real problem.
Can I run the water heater on propane while on shore power?
Yes, and on a combination gas-electric unit you can run both at once: Dometic's manual says the heater is designed to run on gas, electricity, or both, so running both is standard practice when you want hot water faster. The rule that matters either way is the same: never run the electric element with an empty tank.
Sources
- Suburban tank water heaters operation and maintenance guide, part 206244 (PDF, Suburban's own document library)
- Suburban water heater service manual (technician literature, released to service centres rather than published; no maker copy to link)
- Atwood water heater service manual, now Dometic (2004 edition; Dometic publishes operating instructions for these units, not this service manual; no maker copy to link)
- Dometic L.P. gas water heater manual
- Dometic XT 6 and 10 gallon water heater manual, for the statement that fitting an anode rod in place of the drain plug damages the coupling.
- Furrion tankless water heater troubleshooting and service manual, for the TANKLESS unit's relief valve test, the minimum flow rate, and the E1 and E5 code meanings. It is a tankless manual and does not cover the tank-style relief-valve check.