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13 Troubleshooting (continued)
Table 13A Troubleshooting Chart - No Display
FAULT CAUSE CORRECTIVE ACTION
No Display
- No 120 VAC supplied to unit. • Check external line switch, fuse, or breaker.
• Check wiring harness connection between display
board and main control board. Connect
harness at both points.
- Bad display board. • Replace board.
- Bad main control board. • Replace the main control board.
- Blown fuse. • Replace fuse F3 on the main control board, see
page 58 of this manual.
No Burner
Operation
- Tank temperature set point satisfied. • Review temperature setting.
- Unit locked out on fault. • Consult display for specific fault. Refer to fault
descriptions on page 62 of this manual for corrective
actions.
Unit Does Not
Modulate
Above 50%
- Flue sensor open.
• Verify that the flue sensor is located in the flue outlet.
• Check wiring connections at the flue sensor.
• Check the resistance of the flue sensor and compare
to Table 3C on page 60 of this manual.
Installation & Service Manual
TM