HVAC Code Lookup

Trane Furnace Code E4.2

Safety fault

The flame roll-out limit switch has opened. Flame or hot combustion gas came out of the burner box instead of going up the heat exchanger, and the switch shut off all gas flow.

Manual wording: “Open roll-out limit switch”

Documented for: S8V2 two-stage induced draft furnaces (FNR-SVX003A control revision)

Likely causes, most common first

  1. Open roll-out limit switch
  2. Blocked or cracked heat exchanger
  3. Blocked vent or restricted combustion air
  4. Burner or gas pressure problem

What you can safely check yourself

  • Turn the furnace switch off and leave it off
  • If you smell gas or see soot, leave the house and call the gas utility from outside

When to call a technician

Call a technician immediately and do not run the furnace. The manual describes the roll-out device as a thermal control that opens the circuit to shut off all flow of gas; the manual-reset roll-out limit must be reset by a qualified servicer only after the cause is found.

A Trane furnace throwing this code repeatedly has a reason — clearing the code without fixing the cause just hides it.

Source

Other Trane codes