Suburban Tankless Troubleshooting
The Short Answer: A Suburban Nautilus IW60 (on-demand) is not a 6-gallon SW6DE tank. No heat is almost always E1/E2 ignition, flow under ~0.5 GPM, dead 12-volt, an overheat E4/E5, or freeze damage in the small buffer. Photograph the interior control. Soft-reset once. Do not keep firing into a propane smell. Tank Suburbans: SW6DE.
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Search Intent & The Real Problem
The shower died. The coach brochure said Suburban. That badge covers tanks (SW6DE, SW10DE, Phase 3) and the Nautilus on-demand box (IW60 / IW60RL). Forums paste DSI-board steps onto a flow-activated heater that has no standing pilot and no tank ECO in the same place. Girard and Truma hide in the same bays — Girard troubleshooting, AquaGo. Read the rating plate on the door, not the dealer sticker.
What other guides get wrong
They treat Nautilus as an SW6DE with a fancier name. SW6DE stores six gallons; Nautilus fires on flow (~0.5 GPM) and, on RL models, has a small recirc tank that freezes if you skip winterize. They hunt a red ECO button that is not there. They tell you to keep cycling the faucet through an E4 overheat. And they skip 12-volt brownout: a Nautilus that “randomly” E1s at night is often a tired battery, not a gas valve.
Step-by-Step Troubleshooting
Step 1: Prove which Suburban you actually have
| What is in the bay | You want |
|---|---|
| 6- or 10-gallon tank, exterior grate, gas and/or electric switches inside | SW6DE, SW10DE, not working on gas |
| On-demand door, interior control center, fires only when a faucet is open | This page — Nautilus IW60 |
| Lippert/Girard panel, E1 on a different sticker | Girard |
| Truma drawer filter | AquaGo |
- What to look for: Model on the Suburban rating plate (IW60 vs SW6DE vs Phase 3). Interior On Demand Control Center present or not — some IW60s only have a switch-and-light and will not show E-codes.
- Required tools: Phone photo of the plate and the interior panel.
Step 2: Read the Nautilus code — do not guess
Codes below are the common IW60 map with control centers 161252 / 161253. Confirm your sticker. Switch-and-light units lock out with a steady lamp and no digit.
| Code | Meaning | First move |
|---|---|---|
| E1 | Ignition fault — no flame after two tries | LP, 12 V, spark, then lockout |
| E2 | Flame lost during a run | Same fuel/sense path as E1 |
| E3 | Flame sensed before ignition | Leave it off — false flame |
| E4 | Outlet NTC overheat (~194°F / 90°C) | Cool with flow; find why it flashed |
| E5 | Thermal switch open | Overheat limit — not a thermostat click |
| E6 | Air-pressure switch / fan | Exhaust, hose, blower — do not jumper |
| E7 | Inlet NTC open/short | Wiring, then probe |
| E9 | Water NTC open/short | Wiring, then probe |
| EC | Control communication | Cable, then licensed |
- What to look for: The letter twice. Photograph it before you cycle power. No code and no fan = flow, 12 V, or the exterior/interior switch.
- Required tools: Phone camera, flashlight.
E3 and a propane smell are not a reset. Shut bottles.
Step 3: 12 volt, LP, and 0.5 GPM — before parts
- What to look for: Coach battery / converter. Rest voltage around 12.6 V; these boards get stupid under ~10.5 V. Bottles open, regulator not icing, stove lights. Isolation / bypass in the normal path so the pump actually feeds the Nautilus. Inlet screen packed. A 0.4 GPM “water saver” head that never holds activation — burner cycles, shower pulses, then E1/E2.
- Required tools: DC meter if you are qualified. Eyes on bottles. Open a tub spout as a control. No union wrenches.
Nautilus wants LP near 11 in. w.c. at the appliance (plate often ~11–14 in. w.c.). House-tank numbers are different: NG ~3.5–7 in. w.c. / LP ~10–11 in. w.c. — confirm the rating plate. Manometer work is licensed. Do not crack a flare.
Rapid on/off with the pump cycling is often no accumulator, not a dead board. Air in the lines after a fill mimics “no ignition.” Bleed faucets; still do not purge LP fittings.
Step 4: E1 / E2 / E6 — ignition and air, not a tank DSI board
- What to look for: Fan spins, spark you can hear with bottles closed for a spark-only listen, then gas on for one trial. No spark = igniter or board. Spark, no flame = empty bottle, frozen regulator, or a valve that never opens. Flame, then E2 = flame rod, wind in the exhaust, low LP as the tank cools. E6: blocked exhaust, kinked pressure-switch hose, seized blower. Do not jumper the switch to “see if it fires.”
- Required tools: Ears at the exterior door. Bottles closed for spark-only.
Two failed trials and it lockouts. Soft-reset once (faucet off/on or switch off/on) after you fix fuel or 12 V. A third E1 is a tech, not a ritual. Tank-style click-no-light is a different electrode — Suburban igniter does not swap onto a Nautilus.
Step 5: Overheat, freeze, leaks, and a waterway that is actually done
- What to look for: E4/E5: setpoint cranked, low flow so the exchanger flashes, scale from hard-water parks, a failed NTC lying to the board. Let water run to cool, then one reset. IW60RL recirc tank cracked after a freeze — NHTSA-class failure if it was stored wet. Water in the cabinet at the relief, a fitting, or the exchanger. Scale that overheats into repeating E4.
- Required tools: Paper towel. 12 V off. If the board is wet, it stays off.
A cracked exchanger is replacement. There is no honest epoxy repair on a propane on-demand box in a wet bay. Reset procedure for tank Suburbans is a different button: Suburban RV reset.
When DIY Ends: Calling a Licensed Pro
You may photograph a code, confirm bottles and 12 V, clean an inlet screen with power off, open a tub to prove 0.5 GPM, and faucet-cycle once. Stop at a propane smell, E3, a wet board, gas-valve work, a jammed blower, repeating E1/E4, and any freeze-split RL tank. A mobile RV tech who stocks Nautilus probes, fans, and exchangers beats a fifth lockout and a bay full of unburned LP. Wrong SW6DE board in a Nautilus bay is how harnesses melt.
Frequently Asked Questions
Q: Why is my Suburban tankless water heater not working? A: E1/E2 ignition (LP, spark, 12 V), flow under about 0.5 GPM, E4/E5 overheat, a probe (E7/E9), or freeze damage on an IW60RL. No code and no fan is flow or power. Confirm it is not an SW6DE tank.
Q: What does an E1 code mean on a Suburban Nautilus? A: The board tried to light twice and did not prove flame. Bottles, regulator, 12 V, igniter, then the valve. One reset after you fix the cause. A repeat is licensed.
Q: Is a Suburban Nautilus the same as a Suburban SW6DE? A: No. Nautilus is on-demand propane (IW60). SW6DE is a 6-gallon tank with a different board and ECO. Order the rating-plate part, not the coach brand.