HVAC 73 B DISPLAYING BLINK CODES 1. Activate the diagnostic mode. 2. Press the AC button and keep it depressed for 5 seconds or more. 3. The recirculation LED will glow for 5 seconds and be OFF for 5 seconds to confirm that the blink codes will be displayed. 4. After this the recirculation LED will start giving out the blink codes. Pattern A Pattern B ON OFF Blink Code (1,2) 5 sec Start Pulse 5 sec 5 sec 5 sec Stop Pulse Pause after Blink Sequence AC Key pressed and held for 5 seconds to query faults NOTE All faults (permanent, temporary and history) shall be displayed by the control head. The user shall be able to distinguish the permanent and non-permanent (temporary/history) by erasing the faults after querying them once. C READING BLINK CODES A blink code sequence comprises of 2 blink patterns A and B in the sequence A,B. Blink pattern A and B is differentiated by the ON and OFF timing delays: a. Blink Pattern A has 1 second ON time and 1 second OFF time. b. Blink Pattern B has 0.5 seconds ON time and 0.5 seconds OFF time. c. Blink pattern A is followed by Blink Pattern B with a time delay of 2 seconds. A sample blink sequence (2, 2) is indicated as illustrated below. 1s 1s 0.5s 0.5s 2s Pattern A Pattern B Recirc LED Status ON OFF 1s
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