Atwood Water Heater Will Not Stay Lit

The Short Answer: An Atwood/Dometic that lights, then dies, is proving flame and losing it: low LP, a dirty or cracked sense electrode, an ECO, or a one-shot thermal fuse. Watch one trial. Click with no blue is a different page. If you smell propane, shut the bottles. Do not keep hitting the switch. Hire an RV tech.

Search Intent & The Real Problem

Tick, blue puff, dark. Or it runs a minute and the bay goes silent. People call that “won’t stay lit” and buy a 20–30 mV thermocouple for a board that does not use one. Modern Atwood (now Dometic) 6- and 10-gallon DSI heaters have no standing pilot: the board sparks, opens the solenoid, looks for flame on the same rod. Light-then-die is sense, fuel, or a cutoff. Click forever with no flame is Atwood clicking. Generic RV light-then-out covering Suburban too: fires up then goes out. This page is Atwood/Dometic stay-lit.

Electric still making heat means the tank can hold water. Stay on the LP path. Whole-box tree: Atwood troubleshooting. Residential millivolt stay-lit is not this board — won’t stay lit.

What other guides get wrong

They lead with “purge the gas line” on a heater that fired yesterday — do not purge fittings. They mix standing-pilot thermocouples with DSI flame rods. They tell you to jumper the Atwood thermal cutoff “just to test.” And they diagnose gas from the electric switch, so you replace a ~1400 W element because the flame will not hold.

Step-by-Step Troubleshooting

Step 1: Prove it is light-then-die, not click-no-light

• What to look for: Door badge G6, GC6, G10, GC10, WH-6, WH-10. Bypass in normal. Steady stream at a hot faucet. Electric switch off so you do not dry-fire the element. Coach skins (Forest River, Keystone, Thor) are still this heater — Forest River.
• Required tools: Flashlight, cabinet diagram, a hot faucet.

Step 2: LP that looks like a bad board

• What to look for: Bottles actually open. Automatic changeover sitting on two empties. Regulator icing after the furnace, fridge, and heater all drew at once — it lights, starves, lockouts. Other LP appliances dying in the same minute is the tank or regulator, not the DSI module. A cheap regulator that will not hold ~10–11 in. w.c. at the appliance (confirm the rating plate) will light a stove and still drop the water heater. Manometer work is licensed.
• Required tools: LP gauge, eyes on both bottles. No flare wrenches.

Do not crack a fitting to “see if you have gas.” Stove works and the Atwood dies = problem at the heater or a regulator that sags under load.

Step 3: One spark trial with bottles off, then one fire

• What to look for: Bottles off: you should still see/hear spark at the electrode (about a business-card gap). No spark: cracked ceramic, melted high-voltage lead, open thermal fuse, or a dead board. Spark with bottles off, flame with bottles on that dies in 3–8 seconds: the rod is not in the flame, the flame is lifting off the rod, soot, or a spider web in the burner tube. Do not keep cycling into lockout.
• Required tools: Eyes on the electrode with LP off. Interior gas switch.

Soot at the door or flame licking out of the tube is rollout. The next part that opens is often the thermal fuse. Clean with gas off. Do not sand a live electrode.

Step 4: ECO, empty tank, thermal fuse — the “it ran a minute” deaths

• What to look for: Winterize or bypass left on: tank empty, gas tries, high-limit or ECO opens, flame dies. Fill it. Electric ECO is the red or black button on the jacket thermostat — one press on a full tank, 120 V off first — Atwood reset. Electric-only death: Atwood electric. A brown sleeved thermal cutoff in the 12 V path is not that button; if it is open, find the heat, then replace the fuse — never jumper it. DSI lockout: cycle the interior gas switch 15–30 seconds once after a confirmed full tank and confirmed spark.
• Required tools: Full tank, then one reset. Finger, not tape.

Wind down an uncovered flue on a storage night will light, then cook the thermal fuse. Cover off, flue clear, then one trial.

Step 5: Electrode, flue, and a board that is actually dead

• What to look for: Rod cracked, gap huge, wire melted to the jacket, electrode not in the flame envelope. Mud dauber or bird in the exhaust. Water dripping into the burner from a P&T or a drain plug — shut LP; that is a leak, not an igniter — RV bottom leak. Board that clicks a relay and never holds the solenoid after a clean rod, a good fuse, and proven LP is replacement, with the Dometic harness, not a Suburban Phase 3 module — Suburban on gas only if the door says Suburban.
• Required tools: LP off before you touch the rod. The matching part number.

Do not convert “air in the line” into a loosened flare. Air after a bottle swap can delay the first light. It does not excuse a fifth trial into a bay that smells like propane.

When DIY Ends: Calling a Licensed Pro

You may confirm bottles, bypass, a full tank, and watch one spark trial with LP off. Stop at a propane smell, a repeating lockout, a thermal fuse you are tempted to jumper, gas-valve work, and any water in the burner box. A licensed RV tech with a manometer (~10–11 in. w.c. LP at the appliance — confirm the plate) and the correct Dometic board beats a melted harness from an Amazon module. Same-day if it smells.

Frequently Asked Questions

Q: Why won’t my Atwood water heater stay lit? A: Low LP, a dirty or cracked flame-sense electrode, an ECO or thermal fuse, or a DSI lockout. Watch one trial. Click with no flame is a different fault. If it dies again, hire an RV tech.

Q: Is it the thermocouple if my Atwood lights then goes out? A: Only on old standing-pilot Atwoods. Current DSI models use a spark electrode and a board, not a 20–30 mV thermocouple. Wrong part, still no heat.

Q: Can I keep cycling the Atwood switch until it stays lit? A: No. Each failed trial dumps unburned LP into the burner box. One cycle after you prove water, spark, and bottles. Repeating lockout is an RV-tech job.