Fireye NX6300 (Nexus) fault F66: Flame Test
The controller regularly checks that its flame input reads "no flame" when it should, using the scanner shutter or the detector’s own self-check. F66 means that test failed, so the controller can no longer trust the flame input. Left alone, a failing UV tube can show flame that is not there.
Diagnose this with AI
Try Free Boiler Diagnostic Upload a keypad photo, the fault history or a parameter export from your Fireye NX6300 (Nexus). InduQT compares the evidence and suggests the next useful checks.
When it happens
- Any status where the dark check runs; with shuttered or self-check scanners this includes firing
Reading the subset
| Subset | What it tells you |
|---|---|
| 1 | Shutter not detected (shuttered UV) |
| 2 | Flame input circuit failure |
| 3 | Input stuck on, or terminals short-circuited |
| 1xx / 2xx | Self-check detector on flame 1 or flame 2 (when the scanner option is set for it), followed by the codes below |
| +1 | CANbus time-out: check wiring |
| +2 to +4 | Detector memory fault: replace the detector |
| +5, +6 | Detector internal fault: replace the detector |
| +7 | Shutter or dark check failed, or UV tube failed: check the detector out of the burner |
Where it sits in the burner
Supervised functions: Flame supervision, Controller self-checks.
| Component | Signals to look at | How it fails |
|---|---|---|
| Flame scanner (UV / IR) | Flame signal | Detector or amplifier ageing; Electrical noise on signal wiring; Dirty or fogged scanner sight path; Scanner no longer sighted on the flame root |
| Flame amplifier / flame input | Flame signal | Detector or amplifier ageing; Electrical noise on signal wiring; Wrong detector, amplifier or configuration |
| Controller communication network | Burner sequence state | Communication wiring fault; Electrical noise on signal wiring |
Likely causes and checks
1UV tube failing or shutter stuck
- Points to it
- Subset 1 or +7; may be preceded by F11 events.
- Check
- Test the scanner outside the burner as the manual directs; replace if the dark check still fails.
2Flame input wiring short
- Points to it
- Subset 3; after wiring work or cable damage.
- Check
- Check the scanner cable and terminals for shorts.
3Self-check detector fault
- Points to it
- Subsets x02–x06.
- Check
- The manual directs replacing the detector for memory or internal faults.
4CANbus to the detector
- Points to it
- Subset x01.
- Check
- Check CANbus wiring to the detector.
Telling it apart
- F66 is the controller’s test of the flame input; F11 is a flame actually being registered at the wrong time.
Evidence to collect
- Subset
- Scanner model and option setting
- Any recent F11 events in the log
Work on fuel trains, burners, pressure vessels and electrical equipment must be done by qualified personnel following the manufacturer’s documentation and local codes. Never bypass a safety device or interlock.