DSI Fault / Lock-Out

Atwood Water Heater: “DSI Fault / Lock-Out”

warning RV water heater fault codes

Safety You are working around LP (propane) gas and a 12V/120V appliance. Smell for gas before and during testing; if you smell propane, stop, ventilate, and do not create sparks. Repeated manual re-tries dump raw gas into the burner chamber, so never bypass or jumper the ECO or thermal cut-off safety switches. The thermal cut-off trips near 190 F to prevent a fire from a blocked flue, so a part that keeps tripping signals a real overheating hazard, not a nuisance.

What it means

On Atwood DSI (Direct Spark Ignition) water heaters there is no multi-digit numeric code. Instead a single non-ignition (lock-out) lamp lights at the remote ON/OFF switch in the coach. When you switch the heater on, the control board energizes both the gas solenoid valve and the spark electrodes for a trial-for-ignition period of about 6 to 8 seconds. The board makes up to three ignition attempts; if a flame is not proven after the third try, the board stops and goes into lock-out, lighting the fault lamp. The lamp means the unit tried to fire and failed, OR a safety switch (ECO / thermal cut-off) has opened the circuit.

Most likely causes

Low LP gas supply or empty/closed tank, or incorrect gas manifold pressure (should be 11 inch water column under load) most likely
Low DC supply voltage to the board (needs about 10.5 VDC minimum) or weak/dead house battery common
Dirty, cracked, or mis-gapped spark electrodes (gap should be about 1/8 inch) so no spark is produced common
Blocked main burner tube or burner orifice (often spider webs / mud-wasp nests) so gas cannot reach the spark common
Loose, corroded, or open wiring at the ECO, solenoid valve, or the 4-pin connector on the circuit board common
Open ECO (energy cut-off) or open one-shot thermal cut-off fuse breaking the circuit to the board less common
Defective gas solenoid valve or defective circuit board less common

Safe checks you can do yourself

Confirm the LP tank has gas and the valve is open, and that another gas appliance (stove/furnace) lights normally to prove gas pressure and a primed line.
Check the house battery / 12V supply; a low battery can cause repeated lock-outs even when gas is fine.
Switch the water heater OFF, wait, then switch ON again and listen for the rapid clicking of the spark and watch for ignition within the first several seconds.
With power off, inspect the spark electrodes for soot, cracks in the ceramic, or a wrong gap (about 1/8 inch) and gently clean them.
Look into the burner tube and flue for spider webs, insect nests, or soot blocking gas flow or exhaust, and clean the burner tube with a brush (not compressed air).
Tug-test the spade connectors and the 4-pin plug at the circuit board, and check the green ground wire screwed to the flue box for a tight, corrosion-free connection.

How to reset / clear DSI Fault / Lock-Out

Turn the water heater OFF at the remote switch for about 30 seconds to clear the lock-out, then turn it back ON to start a fresh ignition sequence.
If it locks out again, correct the underlying cause (gas, battery, electrodes, blockage) before retrying rather than repeatedly cycling the switch.
If the one-shot thermal cut-off fuse has tripped from overheating, it is a sacrificial part and must be replaced (not reset) after the cause of overheating is removed.

When to call a technician

If gas, battery voltage, electrodes, and blockages all check out but the unit still locks out, or if the ECO/thermal cut-off keeps tripping, or if you smell gas or see scorching around the heater, stop and call a qualified RV technician.

Applies to

G6A-8E · GC6AA-10E · GCH6A-10E · GC10A-4E · GCH10A-4E · GC6AA-7E · GH6-8E · Dometic-branded equivalents (e.g. WH6GEA)

FAQ

What does Atwood Water Heater code "DSI Fault / Lock-Out" mean?

How do I reset Atwood Water Heater DSI Fault / Lock-Out?

Turn the water heater OFF at the remote switch for about 30 seconds to clear the lock-out, then turn it back ON to start a fresh ignition sequence. If it locks out again, correct the underlying cause (gas, battery, electrodes, blockage) before retrying rather than repeatedly cycling the switch. If the one-shot thermal cut-off fuse has tripped from overheating, it is a sacrificial part and must be replaced (not reset) after the cause of overheating is removed.

What is the most common cause of DSI Fault / Lock-Out on a Atwood Water Heater?

The most likely cause is low lp gas supply or empty/closed tank, or incorrect gas manifold pressure (should be 11 inch water column under load).

Related · Atwood water heater

ECO open / tripped
The ECO is a backup high-limit temperature switch wired in s… Gas & spark, no flame proven
A diagnostic sub-condition of the DSI lock-out: both gas and… Gas present, no spark
A diagnostic sub-condition of the DSI lock-out from the offi… No spark / no ignition
Dead unit with no spark at the electrode and no lockout-ligh… Spark present, no gas
A diagnostic sub-condition of the DSI lock-out from the offi… TCO (thermal cut-off) tripped
Current Atwood DSI water heaters have a one-shot thermal cut…

Sources

Atwood Water Heaters Service Manual (Electronic Ignition Models, DSI Sequence of Operation & Trouble Shooting Guide) — DSI Sequence of Operation (Circuit Board: 6-8 sec trial, 3 tries, lock-out + non-ignition lamp); Electronic Ignition Trouble Shooting Guide, effective 2/10/14 (Atwood Mobile Products LLC)
Atwood Water Heater Service Manual — Electronic Ignition / DSI section (Heartland Owners (hosted Atwood manual))

Note: Atwood/Dometic gas-absorption-style water heaters use a single steady lock-out lamp, NOT a counted blink/flash code like Atwood furnaces. Anyone expecting a numbered flash code on this water heater will not find one; the diagnosis is by sub-condition (spark/no spark, gas/no gas) per the trouble-shooting tables.

● Last verified 2026-06-29 · compiled from manufacturer documentation. Codes can vary by model year — always cross-check your unit’s manual.