TCO (thermal cut-off) tripped

Atwood Water Heater: “TCO (thermal cut-off) tripped”

danger RV water heater fault codes

Safety A tripped thermal cut-off means the heater actually overheated, which is a fire-risk condition usually caused by a blocked flue. Do not simply replace the part and run it; find and clear the blockage first. Work with LP off and power off, and never bypass the thermal cut-off.

What it means

Current Atwood DSI water heaters have a one-shot thermal cut-off device on the incoming power wire, connected to the thermostat. It is normally closed and feeds power to the thermostat/board. If excessive heat (around 190 F, typically from a blocked burner tube or flue tube) reaches it, it permanently opens and cuts power to the board, shutting the unit down. It is a sacrificial part like a fuse and must be replaced once tripped; the heater then shows no power / will not fire.

Most likely causes

Blocked main burner tube or flue tube (spider webs, mud-wasp nests, soot) causing flame/heat to roll out and overheat the cut-off most likely
Exhaust grille installed upside-down (wide aluminum band at top) trapping exhaust heat common
Genuine combustion overheating from misalignment or improper installation less common
Defective thermal cut-off device less common

Safe checks you can do yourself

With power off, inspect and clean the main burner tube and the flue tube for insect nests and soot (brush the burner tube, swab the flue).
Check the access-door grille orientation; the wide aluminum band should be at the BOTTOM, not the top.
With a multimeter, check continuity across the thermal cut-off; an open device with the unit cold confirms it has tripped and needs replacement.

How to reset / clear TCO (thermal cut-off) tripped

The thermal cut-off cannot be reset; it must be replaced after the cause of overheating is removed.
Clear all flue/burner obstructions and correct grille orientation before installing a new cut-off, then power up and test.

When to call a technician

If you cannot find the obstruction, if there is heat/scorch damage, or if a new thermal cut-off trips again, stop and call a qualified RV technician immediately.

Applies to

G6A-8E · GC6AA-10E · GCH6A-10E · GC10A-4E · GCH10A-4E

FAQ

What does Atwood Water Heater code "TCO (thermal cut-off) tripped" mean?

How do I reset Atwood Water Heater TCO (thermal cut-off) tripped?

The thermal cut-off cannot be reset; it must be replaced after the cause of overheating is removed. Clear all flue/burner obstructions and correct grille orientation before installing a new cut-off, then power up and test.

What is the most common cause of TCO (thermal cut-off) tripped on a Atwood Water Heater?

The most likely cause is blocked main burner tube or flue tube (spider webs, mud-wasp nests, soot) causing flame/heat to roll out and overheat the cut-off.

Related · Atwood water heater

DSI Fault / Lock-Out
On Atwood DSI (Direct Spark Ignition) water heaters there is… 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…

Sources

Atwood Water Heaters Service Manual (Thermal Cut-Off Device; DSI Sequence of Operation) — THERMAL CUT-OFF DEVICE section (one-shot, trips ~190F from blocked burner/flue, breaks circuit, sacrificial); DSI Sequence of Operation 'Thermal Cut-Off' (Atwood Mobile Products LLC)

Note: The thermal cut-off is distinct from the ECO: it is on the incoming power wire and is non-resettable. Trip temperature (~190 F) and details are from the Atwood manual; confirm against the specific unit.

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