Suburban Tankless Troubleshooting
On this page (6 sections)
The Short Answer: Suburban’s Nautilus on-demand heater (IW60 series) fires only when hot water flows through it, and it needs 12-volt power and propane. When it will not heat, check that a hot tap is open wide enough to start it, that the battery is charged, and that propane reaches the coach, then read any code on the control panel. Repeated ignition failures, overheat codes, or a propane smell need an RV technician.
Make sure it is the Nautilus
Suburban makes both tank heaters (SW6DE, SW10DE and others) and the Nautilus on-demand heater. They are not interchangeable. The model label inside the outside access door shows which you have. If it is a tank model, see SW6DE or SW10DE troubleshooting instead.
How the Nautilus decides to fire
When water flow through the heater rises above its minimum, the control starts the combustion fan, proves airflow, sparks, and opens the gas valve. It modulates the flame to hit the set temperature. If flow drops below the minimum, it shuts off. That is why a low-flow shower head, a partly closed valve, or a clogged inlet screen can produce cold or pulsing water even though nothing is broken.
Some Nautilus installations have an interior control center with a display that shows letter-number codes; others have only a switch and an indicator light. Suburban has used different control panels over the years, so use the code chart in the manual for your model and control rather than a generic list. Codes that indicate ignition failure, flame loss, overheating, or an air-pressure (fan or vent) fault are common categories on these heaters.
Symptoms and where they point
| Symptom | Likely direction | Owner action |
|---|---|---|
| Nothing happens, no fan, no code | Not enough flow, switch off, no 12 V | Open a hot tap fully; check switch and battery |
| Fan runs, clicks, no flame, then a code | No propane, air in the line, ignition fault | Check cylinders and stove; one reset |
| Lights, then cuts out mid-shower | Flow dropping below minimum, low LP, flame sensing | Try a higher flow; note when it happens |
| Hot, then very hot, then off with a code | Overheat limit, scale, very low flow | Stop; let it cool; call |
| Code pointing to air or fan | Blocked exhaust or intake, fan fault | Look at the outside vent for obstructions |
| Water dripping from the cabinet | Fitting leak or freeze damage | Turn off water and the heater; call |
What you can check safely
- Flow. Open the hot tap fully at a sink or tub. If the heater fires there but not at the shower, the shower head or mixing valve is limiting flow.
- 12-volt power. Check the battery on the monitor panel. Low voltage causes failed ignitions and erratic shutdowns.
- Propane. Cylinder open and not empty; the stove lights.
- Bypass and fill. After winterizing, set the bypass back to normal and run water until there is no air.
- The outside vent. Look for insect nests, ice, or debris at the vent and intake.
- One reset. Turn the heater switch off and on once after fixing anything obvious. If the same code returns, stop.
What the technician will check
An RV technician will confirm LP pressure at the heater, inspect the igniter, flame sensor, gas valve, combustion fan, and air-pressure switch, and check the water-side sensors and flow sensor. On units used in hard-water areas, they may descale the heat exchanger. A frozen and split heat exchanger or water line is the main reason for replacing the heater; Nautilus units must be drained or protected for winter like any RV plumbing.
For other brands in the same kind of bay, see Girard tankless troubleshooting and Truma AquaGo problems.
Frequently Asked Questions
Q: Why does my shower go hot, cold, hot? A: Usually the flow is hovering around the heater’s minimum, so it keeps shutting off and restarting. Use a shower head and valve setting that keep a steady flow, and have the inlet screen checked if flow is weak at every tap.
Q: Can I reset the code by turning the power off? A: Cycling the switch once is reasonable after you fix an obvious cause like an empty cylinder. Repeated resets after ignition failures can send unburned propane into the burner, so stop and call a technician.
Manuals and supporting references
These links distinguish general safety information from model-specific documentation. A manual directory helps you locate your unit’s instructions; it does not establish that every model uses the same parts, codes, or test values.
- Suburban: service and support (opens in a new tab)Identify the appliance behind the RV badge and obtain its operating instructions.
- PG&E: recognizing and responding to a gas leak (opens in a new tab)Emergency actions for suspected fuel-gas leaks.
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