TM
Installation & Service Manual
13 Troubleshooting (continued)
Table 13A Troubleshooting Chart - No Display
FAULT | CAUSE |
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| - No 120 VAC supplied to unit. | • | Check external line switch, fuse, or breaker. |
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| • Check | wiring | harness | connection | between | display | |
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| board | and | main | control board. Connect | ||
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| harness at both points. |
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No Display |
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- Bad display board. | • | Replace board. |
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| - Bad main control board. | • | Replace the main control board. |
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| - Blown fuse. | • | Replace fuse F3 on the main control board, see | |||||
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| page 58 of this manual. |
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| - Tank temperature set point satisfied. | • | Review temperature setting. |
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No Burner |
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Operation | - Unit locked out on fault. | • | Consult display for specific fault. | Refer | to fault | |||
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| descriptions on page 62 of this manual for corrective | |||||
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| - Flue sensor open. | • | Verify that the flue sensor is located in the flue outlet. | |||||
Unit Does Not |
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Modulate |
| • | Check wiring connections at the flue sensor. |
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Above 50% |
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| • | Check the resistance of the flue sensor and compare | ||||||
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| to Table 3C on page 60 of this manual. |
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59 
