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Fan error
1. Is Combustion Air Blower operating?
Yes: -> 2.
No: -> 4.
2. Disconnect 4-wire harness from Combustion Air Blower. Does Combustion Air Blower speed increase?
Yes: -> 3.
No: Replace Combustion Air Blower.
3. Disconnect harness from Control Module J9. Continuity in each wire of 4-wire harness (yellow, red, white, black)?
Yes: Replace Control Module.
No: Replace harness.
4. Are 3-wire and 4-wire harnesses connected to Combustion Air Blower?
Yes: -> 5.
No: Connect harness.
5. Disconnect harness from Control Module J9. Measure voltage between J9-2 and J9-3. Is voltage 120 Vac ± 10%
Yes: -> 6.
No: Replace Control Module.
6. Disconnect 3-wire harness from Combustion Air Blower. Measure continuity in each wire. Continuity in each wire?
Yes: Replace Combustion Air Blower.
No: Replace harness
