When an RV water heater is not working, most people assume it means a dead unit. It usually does not. The majority of no-hot-water problems trace to one small part, a flipped switch, a valve left in winter mode, or a safety reset that tripped and needs a press. This guide walks the system like a technician does: decide which side is broken, propane or electric, then work the cheap checks before anything expensive.
Last reviewed: Sep 21, 2026, against current Suburban and Atwood service guidance. We update these guides when real-world data changes.
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.
If the RV was winterized and the drain plug or anode was left out, the tank is empty. An empty tank can burn out the electric element in seconds. Open a hot faucet and confirm steady water; if it sputters and stops, the tank is empty. Never run the electric element with no water in the tank. This is the single most common winter-to-spring mistake, and it is the most expensive small error on this page.
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.
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.
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.
Behind the same exterior access panel sits the emergency cutoff, or ECO, a high-limit safety switch that shuts down the electric element if the water overheats, typically around 180 degrees. It exists to stop the element if the thermostat fails and lets the tank run away. When it trips, the electric side goes dead, and it stays dead until someone resets it, which is why a heater can simply stop working one day with no other symptom.
Most units have a small reset button, often red, under the exterior access panel or on the thermostat assembly. Press and release it. If the ECO was tripped, electric mode comes back immediately. If it trips again right away, the real problem is upstream, usually a failed thermostat or heavy sediment, and the reset is a diagnostic result, not a repair. Find the reset, learn what your heater's reset looks like, and put it in the routine so a tripped ECO never sends you shopping for parts you did not need.
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.
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 about 6 to 8 seconds then stops, that is a safety lockout: the unit did not detect a flame and is protecting itself. Turn the heater off, wait, 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, and one of the most common fixes in the trade.
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, shows the tell, bulging or chalky white residue on the element. 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, buy the same rating, do not guess wattage.
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.
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 an aftermarket anode rod installed in an Atwood aluminum tank can seize in the threads due to the metal reaction, so do not add one.
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.
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; 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. Usually a combustion problem, a dirty burner or a blocked vent. If you smell ammonia or see heavy soot, stop using the propane side and have it looked at, because a combustion problem can become a safety problem.
You can reasonably replace the heating element, the thermostat, the ECO, the fuses, and the anode rod, and you can clean the burner. The checks on this page, tank level, bypass mode, both switches, the ECO reset, and the element test, are all owner territory. 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 about the labor separately, because RVers replace these water heaters regularly.
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.
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.
Disconnect power first. Set the meter to ohms. Touch the probes to the two element terminals, a healthy element reads a low resistance, a dead one reads open. 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.
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.
The emergency cutoff is a high-limit safety switch that kills the electric element if the water overheats, usually around 180 degrees. When it trips, the electric side goes dead until someone presses the reset button, often red and located behind the exterior access panel. Pressing it often brings a dead electric heater back immediately; if it trips again, the thermostat or sediment is the real problem.
Yes, most units run one heat source at a time from the selector switch, and propane is the higher-output option. Running both at once on older units can draw more current, so follow your model's switch. The important rule is never run the electric element with an empty tank.