3 flashes pause 4 flashes
Thermistor out of range
This code typically points to
- Sensor reading outside valid range
- Poor sensor placement (manual warns nuisance 'out of frame' faults if outdoor-air thermistor is not placed properly under the base pan)
Next checks to confirm
- Verify sensor placement
- Verify actual thermistor resistance vs temperature
Escalation
Repeated fault after proper placement points toward sensor/control issue.
Reset behavior
No public reset timing documented in install/start-up manual.
Service Soon
Schedule repair