Cause of error code A08

Blower speed does not reach speed calculated by Control Module.

Solution for error code A08

1. Is combustion air blower operating? 
Yes: -> 2 
No: -> 4

2. Disconnect 4-wire harnass 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 en 4-wire harnesses connected to combustion air blower? 
Yes: -> 5
No: Connect harness

5. Disconnect harness from control module J9 connector. Measure voltage between two pins, J9-2 and J9-3 on control module. Is voltage 120Vac=/-10% available? 
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 
No: Replace harness.