Rational Combi Oven Ignition Controller Error 18: Flame After Shutoff
Ignition controller error 18 on a gas SelfCookingCenter or iCombi oven means a flame current was measured ten seconds after the gas valve closed on the top hot air burner. Turn off the gas valve to the oven and avoid restarting it. Tell us the number and when you first saw it.
High: a critical gas error that can lock cooking and may involve a valve that does not close.
- Code
- Ignition controller error 18
- Maker
- Rational
- Equipment
- Combi ovens
- Applies to
- Automatic ignition controller (SCC / iCombi gas units)
What does Rational Ignition controller error 18 mean?
After a burner cycle ends and the gas valve closes, the flame should go out and the flame current should drop to nothing. The automatic ignition controller on gas Rational ovens checks this. Error 18 means flame current was still present ten seconds after the gas valve closed on the top hot air burner, which suggests a flame signal remained after the gas should have stopped. Each occurrence is logged as a critical gas error toward Service 140, and enough of them lock cooking. The reason can be a damaged electrode that holds a signal, a gas valve that closes slowly or sticks open, a controller that reports flame after shutoff, or gas pressure or connections feeding the burner unevenly. A valve that sticks open means gas is still reaching the burner, which is the reason a gas smell sends you out of the building. The signal can also be false, a wire or electrode problem that makes a dead burner look lit. Which of the two it is cannot be decided from the display, so a technician tests the valve and the signal separately.
Affected models and control systems
This applies to the automatic ignition controller on gas Rational SelfCookingCenter and iCombi ovens, per Technical Information TI_2220. Error 38 is the bottom burner counterpart on floor-standing models.
Code numbers and their meaning can change between control generations. We match the full model and control before acting on a code.
What you may notice
- Ignition controller error 18 on the display
- Burner lockout after a cycle ends
- A Service 140 message after repeated errors
- Cooking blocked on the oven
Possible causes
Listed in Rational's documentation
- Flame signal that lingers because the top electrode is damaged
- Top burner gas valve that closes slowly or sticks open
- Top burner ignition controller that reports flame after shutoff
- Gas pressure or connections feeding the top burner unevenly
Other likely causes — what usually sits behind Ignition controller error 18 on this control. A technician confirms which one it is before any part is replaced.
- Carbon bridge on the electrode that conducts after the flame is out
- Valve spring weakened so the valve closes late
- Gas supply pressure that surges when other appliances shut off
Safe checks before calling for service
- Turn off the gas valve to the oven.
- Any gas smell means leaving the building and phoning the utility from outside, away from switches.
- Do not keep restarting the oven.
- Tell us the number and when you first saw it. Leave the panels and the burner area closed.
How a technician diagnoses Ignition controller error 18
- Read the error log and the Service 140 count.
- Check supply pressure and connections with the oven off.
- Inspect the electrode, ceramic and sensing wire on the top burner.
- Test whether the gas valve closes promptly and seals.
- Measure the flame current signal after shutoff.
- Replace the failed part and run a full cycle with a gas leak check.
- A valve that closes slowly or sticks open is a gas safety issue that needs test equipment.
- Electrode and igniter checks happen near hot parts and high-voltage ignition circuits.
- Repeated restarts add to the Service 140 count and can lock the oven for cooking.
How Ignition controller error 18 differs from similar codes
Error 18 is flame after shutoff on the top burner. Error 17 is flame before gas opens, and error 38 is the bottom burner version of this one.
Technical reference
- Document
- Technical Information TI_2220 New gas service messages 140
- Edition
- TI_2220_en-GB V02.1, 05/2023 (sheet dated 21/09/2022, series 2022/20)
- Models / control
- Automatic ignition controller (SCC / iCombi gas units)
- Section
- Trigger criteria and warning levels, printed pp. 1-2 of 4 (Service 140.4 / 140.8); ignition controller error list 17, 18, 22, 37, 38, 42 on p. 3-4 near the end of the sheet
- Checked
- October 2026
We use the maker's document to read the code and do not reproduce it. Always confirm the complete model and control before applying these steps.
Related Rational combi oven error codes
Does error 18 mean gas is still flowing?
It may, or the signal may be false. Shut the gas and have it tested.
How is it different from error 17?
Error 17 is flame detected before the valve opens, while 18 is flame detected after it closes.
Will the oven cook again by itself?
Not once Service 140 has locked it.
Need help with Rational Ignition controller error 18?
A technician confirms the cause on site and gives you the price in writing before any work starts.