When an RV water heater not working on electric or gas fails in both modes at once, check the parts both modes share: 12V DC power, the control board fuse, the thermal cutoff and the ECO. Dometic's manual (October 2019) specifies a 2 amp board fuse and 10 to 14 VDC.
Figures checked September 2026. Part prices are retailer listings loaded on that date.
| What you see | Shared or one mode | Parts to suspect | Owner check or technician |
|---|---|---|---|
| Nothing on gas or electric, no lockout light | Shared | 12V supply, board fuse, wall switch | Owner: battery, fuse, switch |
| Both dead, came back after reseating board plugs | Shared | Loose board connector | Owner, power off |
| Both dead on Atwood/Dometic combo, light on | Shared | Thermal cutoff, ECO | Technician if cutoff is heat-damaged |
| Gas works, electric does not | Electric only | 120V breaker, element switch, relay, element | Owner to breaker; technician inside junction box |
| Electric works, gas does not | Gas only | LP supply, burner tube, electrode, gas valve | Owner to LP valve and burner tube; technician for valve |
Because on many combination units the electric side depends on the same 12V control circuit as the gas side. Atwood's January 2007 sequence for the GC6A-10E and GC10A-4E sends power for gas, electric or both through the thermostat and thermal cutoff, then uses a 12V board wire to close the 120V relay. Lose that path and both modes stop.
The Atwood service manual (page 25) also says that if the ECO or the gas valve coils are open, the board will not send power to the yellow relay wire, so the electric element never gets 120V even though shore power is fine. Its quick diagnostic also says to confirm the Molex connector is making contact.
Dometic's WH-6GEA works the same way in outline. Per Dometic's manual (Form 94035, October 2019, sections 5.1.2 and 6.1), the electric switch closes a relay that passes 110 VAC to the element, and the thermal cut-off sits in the power supply line. When the cut-off melts, the heater shuts down.
A common forum answer blames a burned-out element for losing both modes. Atwood's own sequence does not support that: the element sits only on the relay side, after the shared parts. Check the shared parts before buying an element.
Older Atwood units (3E and 9E and earlier) used two separate switches, one 12V DC for gas and one 120V AC for electric, per the same manual.
Start with 12V power and work toward the burner, one shared part at a time. Per Dometic's manual (October 2019, section 6.1), check the board fuse, then voltage above 14 or below 10 VDC, then debris in the burner and flue, then the thermal cut-off. Turn the heater off before you open anything.
For basics that apply to any tank, see our home water heater not working guide.
Most RV water heaters reset by turning the wall switch off, waiting, and turning it back on; some also have an ECO reset button. Per Suburban's operation guide (March 2023), switch off, wait five seconds and switch on. A thermal cutoff that has opened cannot be reset; it is replaced.
| Brand and model | Lockout reset | ECO | Thermal cutoff | Source |
|---|---|---|---|---|
| Suburban D, DE, DEL | Switch off 5 seconds, then on; 15 second purge before each of three tries | "Re-setable" high limit with reset button | Not described in these manuals | Suburban guide p. 5 (Mar 2023); service manual p. 21 |
| Dometic WH-6GA, WH-6GEA, WH-9GEA | Off then on; if the light stays on over 15 seconds, off for 5 minutes | Locks out; reset by cycling the switch after cooling (off 30 seconds) | Melts; must be replaced | Form 94035 §5.1, §5.2, §6.1 (Oct 2019) |
| Atwood GC6AA-10E, GC10A-4E | Switch off and on after the three-try lockout | Gas side opens above 180°F; electric side is a manual reset, trips above 170°F | One-shot, opens at 190°F | Atwood manual p. 12, p. 16 (1998 to 2007) |
Per Dometic, October 2019 (section 5.2), a high-temperature lockout means something overheated: let the water cool, find the cause, and only then reset. If it keeps locking out, call a technician.
The electric side has its own 120V supply, switch and element, so check those first. On a Suburban DE, the electric switch is behind the exterior access door in the lower left corner of the control housing, per Suburban's operation guide (March 2023, page 6). If it is off, the element never heats.
Checks in order:
Our thermostat replacement cost guide shows how thermostat pricing works for home units.
The gas side has its own supply, ignition and valve, and on a Dometic its lockout light can stay dark while electric is on. Per Dometic's manual (October 2019, section 5.1.3), a gas lockout does not light the lamp while electric mode runs. Turn electric off and the lamp shows the gas fault.
From there, per Suburban's service manual (page 14), the burner will not come on if the switch is off, the gas supply is empty or off, or the ECO reset button has tripped. Its troubleshooting chart puts correct gas pressure at 11 to 14 inches of water column. Dometic, October 2019, asks for 11 inches with three appliances running.
A first start after storage can take several ignition cycles to purge air from the gas line, per Suburban's March 2023 guide. Burner, gas valve and pressure work belong with a technician. Our gas water heater pilot and valve repair page explains the household versions of those parts.
Measure its resistance with power off: Suburban lists 10 ohms for its 1440 watt, 120 VAC element. Per the Suburban service manual (file dated February 2021, pages 18 and 19), an open reading means a failed element. Atwood's manual adds a second test: any continuity to the element flange means a short.
Suburban's manual says the most common electric failure is energizing the heater before it is filled, and that even brief dry operation burns out the element. Our element replacement cost guide covers the part and labor side for home tanks.
ECOs on these units reset; thermal cutoffs do not. The Dometic/Atwood 93866 thermal cutoff listed at $24.99 at Panther RV Products in September 2026, and Panther lists it for the WH-6GA, WH-6GEA, GC6AA-10E and GC10A-4E among others. A blown cutoff usually points to a burner or flue problem.
| Part | Listing 1 (Sep 2026) | Listing 2 (Sep 2026) |
|---|---|---|
| Dometic/Atwood 93866 thermal cut-off | $24.99, Panther RV Products | $32.99 for a 2-pack, United RV Parts |
| Dometic/Atwood 91447 thermostat/ECO | $20.00, Panther RV Products | $21.99, United RV Parts |
Per Camping World, July 2026, an RV thermostat runs $40 to $80 and an element $30 to $60 in parts. We found no dated, published hourly rate for RV technicians, so labor is not estimated here; it varies by shop. Our camper water heater repair costs page lists board and valve prices.
Atwood's manual says heat-damaged cutoffs are not warranty items, and that the burner, alignment and gas pressure should be checked before a new cutoff goes in. It also notes that a door grill installed with its wide aluminum band at the top can trap exhaust heat and trip the cutoff.
RV safety. If you smell gas, follow Suburban's guide (March 2023): get everyone out, shut off the gas at the container, and do not touch switches or start the engine or generator. Turn the breaker off before opening the 120V junction box.
Never energize the electric element on an empty tank, and take the bypass valve out of bypass before you switch on. Per Atwood's service manual (pages effective through 2007), if an element runs dry, let the tank cool for 2 to 3 hours before adding water, or it could collapse. Per Dometic, October 2019, if the heater sat unused for more than two weeks, run a hot faucet for several minutes first to clear any hydrogen.
Stop and call an RV technician if you see soot, smell propane, find a melted thermal cutoff, or the lockout returns after one reset.
| Situation | Usual call | Why |
|---|---|---|
| Fuse, connector, breaker or switch | Repair | Low-cost parts, owner-level checks |
| Thermal cutoff or ECO failed once | Repair, after finding the heat source | Dometic and Atwood both say remove the cause first |
| Element or thermostat failed | Repair | Parts priced above; see Camping World, July 2026 |
| Board failed and unit is old, or tank leaks | Compare with a new unit | See our RV water heater replacement prices |
Suburban's service manual shows a reset button on its thermostat and ECO assembly, with the controls at the front of the heater. Atwood's manual-reset electric ECO sits with the 120V parts on the back of the heater, inside the coach. Dometic's October 2019 manual resets lockouts with the wall switch.
On combination units that switch the element through a 12V relay, yes. Atwood's service manual shows the 4E and 10E board energizing the relay over a 12V wire, so without enough DC power, the relay does not pass 120V to the element.
Dometic's October 2019 manual says both modes can run together for quicker recovery, and Atwood says the same for its combination units. On a Dometic, the gas lockout light will not show while electric runs.
Dometic's manual says gas appliances must not run while the vehicle moves, because wind can push the flame back and trip the thermal cutoff, which then has to be replaced. Turn gas off at the tank before driving.
Independent Research
Published ranges for tank, tankless and heat pump replacement, the failures that justify a repair, and the ones that do not. Sourced, dated, and free to read.
