Corrective Action - Crest Audio FBN0751 Service Manual

3
Troubleshooting
Table 3A Troubleshooting Chart - No Display
FAULT
- No 120 vac supplied to unit.
No Display
- No voltage through the switch.
- Bad display board.
- Bad main control board.
- Blown fuse.
- Main control board temperature set point
satisfied.
- Remote thermostat satisfied.
No Burner
- Outside air temperature above Warm
Operation
Weather Shutdown (WWSD) set point for
main control board.
- Unit locked out on fault.
- Ramp delay active.
Unit Does Not
Modulate
Up to 100%
- Boiler controlled by BMS.
38
CAUSE

CORRECTIVE ACTION

• Check external line switch, fuse, or breaker.
• Check position of ON/OFF switch. Turn switch to the
ON position.
• Check 120 vac through the ON/OFF switch.
• Check wiring harness connection between display
board and main control
harness at both points.
• Replace switch.
• Replace board.
• Replace the main control board.
• Replace fuse F2 on the main control board, see
page 37 of this manual.
• Review temperature setting.
• Review remote thermostat setting.
• Check location of outside air sensor.
resistance of outdoor air sensor and compare to Table
3C on page 39 of this manual.
• Consult display for specific fault.
descriptions on page 41 of this manual for corrective
actions.
• Check ramp delay parameter settings. Optional PC
software required.
• Turn ramp delay feature off. See page 20 of this
manual for instructions on how to turn this feature off.
• Check BMS parameter settings.
Service Manual
board. Connect
Check
Refer to fault