Daikin DP14UM Service Instructions Manual page 33

SERVICING
9. If the microamp reading is less than the minimum
specified, check for high resistance wiring
connections, the distance (3/16") between the sensor
and burner, flame sensor connections, dirty flame
sensor or poor grounding.
10. If no reading, check for continuity on all components
and if good - replace ignition control module.
NOTE: Contaminated fuel or combustion air can create a
nearly invisible coating on the flame sensor. This coating
works as an insulator causing a loss in the flame sense
signal. If this situation occurs the flame sensor must
be cleaned with steel wool. Do not use sandpaper, the
silicone in sandpaper will further contaminate the sensor.
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