17
Four Flashes – Unit in Lockout From Failed Ignition/
Flame Loss – Unit Sparks but Doesn’t Ignite
The information below is related to situations where the unit is in lockout from failed
ignition or ame loss. The unit sparks but DOES NOT IGNITE:
Unit Sequence:
• Green light on, call for heat, 24 VAC at R & W terminals
• Power exhauster cycles on, start pre-purge, 24 VAC through pressure switch
and limits
• Igniter sparks, no ignition, no yellow ame sensor light
• Unit will cycle ve times in this manner, then the green light will ash four
times. Power exhauster will cycle off and fan motor will never cycle on.
Possible Causes:
• Gas valve in “off” position
• No 24 VAC from board to gas valve
• Loose wires
– Wire off gas valve
• Excessive inlet pressure
• Low or no gas pressure to inlet of valve (purge lines)
• Defective gas valve
– Verify and replace if required
• Defective board
– Now allowing ignition
– For more information on xing or replacing a defective board,
reference page 23.
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