Suburban Water Heater: “DSI lockout”
warning RV water heater fault codes
What it means
Suburban gas (DSI) water heaters do not show a numeric fault code. When you flip the LP switch, a small panel indicator lights for roughly 15 seconds while the board purges the line and tries to light the burner about 3 times over the next ~6 seconds. If it never proves a flame, the board locks out LP operation for safety and the indicator light stays lit, signaling a failed-ignition lockout. A separate failure mode is no ignition attempt at all (light may not engage normally), which usually points to a tripped 12V high-limit/ECO, low battery voltage, or no spark.
Most likely causes
- Out of propane, closed tank valve, or tripped excess-flow (overfilled/valve opened too fast) starving gas flow most likely
- Low 12V DC supply (under ~12V) so the control board misfires common
- Dirty or insect-blocked burner tube / air intake preventing a clean flame common
- Failing or misadjusted spark electrode (no spark or weak spark) or fouled flame sense via the spark wire common
- Tripped 12V high-limit/ECO so the board never starts the ignition sequence less common
- Failed gas valve, circuit board, or LP regulator delivering wrong pressure less common
Safe checks you can do yourself
- Confirm there is propane in the tank, the tank valve is fully open, and another appliance (stove, furnace) lights normally to prove gas flow.
- Check the RV battery / 12V supply is at a healthy voltage; low voltage commonly causes intermittent no-light, especially when boondocking.
- Verify the dedicated 12V fuse for the water heater is good.
- Look at the outside burner area for insect nests, mud-dauber webs, or debris in the burner tube / air intake and gently clear it.
- Press the reset button(s) on the back of the water heater (the LP side reset is for the 12V/gas circuit), then retry.
- Confirm the tank is full of water before any heating attempt.
How to reset / clear DSI lockout
- Turn the LP switch OFF and wait at least 10 seconds, then turn it back ON to retry the ignition sequence.
- If an over-temperature (ECO/high-limit) trip is suspected, press both reset buttons on the rear of the water heater, then retry the LP switch.
- If the water is already hot, note the board may not attempt ignition until tank water drops below about 100°F.
When to call a technician
Call a certified RV tech if the unit still won't light after confirming gas, 12V power, and a clean burner — or if you suspect the gas valve, control board, regulator/gas pressure, or flame-sensing circuit. Propane pressure (about 11 inches water column) requires specialized tools to verify.
Applies to
SW6DE · SW6DEL · SW10DE · SW10DEL · SW12DE · SW16DE · Suburban DSI gas/electric RV water heaters (5-16 gal)
FAQ
What does Suburban Water Heater code "DSI lockout" mean?
Suburban gas (DSI) water heaters do not show a numeric fault code. When you flip the LP switch, a small panel indicator lights for roughly 15 seconds while the board purges the line and tries to light the burner about 3 times over the next ~6 seconds. If it never proves a flame, the board locks out LP operation for safety and the indicator light stays lit, signaling a failed-ignition lockout. A separate failure mode is no ignition attempt at all (light may not engage normally), which usually points to a tripped 12V high-limit/ECO, low battery voltage, or no spark.
How do I reset Suburban Water Heater DSI lockout?
Turn the LP switch OFF and wait at least 10 seconds, then turn it back ON to retry the ignition sequence. If an over-temperature (ECO/high-limit) trip is suspected, press both reset buttons on the rear of the water heater, then retry the LP switch. If the water is already hot, note the board may not attempt ignition until tank water drops below about 100°F.
What is the most common cause of DSI lockout on a Suburban Water Heater?
The most likely cause is out of propane, closed tank valve, or tripped excess-flow (overfilled/valve opened too fast) starving gas flow.
Related · Suburban water heater
On gas/electric (DE) models, the 120V electric heating circu… Electric element no heat
On gas/electric models, the 120V element produces no heat or… Gas ECO tripped
The gas-side ECO (Energy/Electric Cut Off, a high-limit ther… Gas valve won't open
The board is sequencing and spark is present, but the gas va… No reset light
On a DSI SW-series unit, the reset light failing to come on … No spark / no ignition
The control board is powered and attempting to light (reset …
Sources
- Water Heater Troubleshooting & Repair (Suburban), Version 1.3 — Troubleshooting LP Mode; Hi-Limit/ECO Switch and Thermostat Assembly (pp. 11-12) (Heartland Owners Forum (owner-compiled, references Suburban product docs))
- Suburban Water Heater Service Manual — DSI ignition / LP troubleshooting section (Suburban (hosted by My RV Works, Inc.))
Note: Suburban gas water heaters use a lockout LED/indicator behavior, not a numeric or blink-count fault code, so there is no 'code' to read — diagnosis is by symptom. The 3 light attempts / ~15-second indicator timing and the 10-second OFF reset are from the Heartland-compiled Suburban troubleshooting guide; exact panel-light wording varies by RV manufacturer's switch panel. Always cross-check the specific model's Suburban owner manual.
● Last verified 2026-06-29 · compiled from manufacturer documentation. Codes can vary by model year — always cross-check your unit’s manual.