13
One Flash – Pressure Switch Won’t Close
The below troubleshooting information is related to situations where the power
exhauster DOES cycle on:
Unit Sequence: Green light on, call for heat, 24 VAC at R & W, power exhauster
cycles on after approximately 30 seconds, Green light will give one ash.
• When there is a one ash troubleshooting code, it is indicating that the
pressure switch is not closing within 30 seconds of the power exhauster
being energized.
Possible Causes:
Blockage in tubing to pressure or venting is not allowing for a proper vacuum to pull
pressure switch contacts closed. To solve this issue, troubleshoot the units venting.
• Wire off pressure switch
• 24 VAC not coming from board
• Defective pressure switch
– If this is the case, verify the switch is defective and replace.
For more information, visit www.youtube.com/ModineHVAC and watch the
video on venting.
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