Honeywell 7800 Series Burner Control (RM7800 / RM7840)
Honeywell 7800 Series Burner Control (RM7800 / RM7840) *Flame Detected*: Flame Detected
The control saw an unexpected flame signal while the shutter was open during prepurge, which causes the burner control to lock out.
- Code
- *Flame Detected*
- Name
- Flame Detected
- Controller
- Honeywell 7800 Series Burner Control (RM7800 / RM7840)
- Type
- Flame failure
- What it does
- Lockout: the control shuts down and stays off until it is reset
- Risk
- RED Specialist territory
- Reset
- Needs a manual reset
- Source
- The manufacturer's manual (subscribers see which manual and page)
Updated July 22, 2026
How to fix it
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- What to do next, in plain words
- Which manufacturer manual it comes from, linked
- The 4 common causes listed for this code
- The step by step check for this problem, one check at a time
- Booking a live video call with Ben, a master booth technician ($250/hr, paid per call)
Questions about this code
What does Honeywell 7800 Series Burner Control (RM7800 / RM7840) *Flame Detected* mean?
The control saw an unexpected flame signal while the shutter was open during prepurge, which causes the burner control to lock out.
Is Honeywell 7800 Series Burner Control (RM7800 / RM7840) *Flame Detected* dangerous?
It is graded red, specialist territory: it involves a burner, gas, flame or safety lockout, so leave the repair to a qualified technician.
How do I fix Honeywell 7800 Series Burner Control (RM7800 / RM7840) *Flame Detected*?
The manual's fix and the step by step check for this code are in WERCS Diagnose, plans from $49 a month. For help right now, WERCS answers 24/7 at (877) 489-3727.
Other Honeywell 7800 Series Burner Control (RM7800 / RM7840) codes
All 8 Honeywell 7800 Series Burner Control (RM7800 / RM7840) codes · Every fault code