Pioneer YN018GMFI16M2D Service Manual page 35

Pic 1: Measure the voltage of L2 to S (Vs), is it
moving alternately between positive value and
negative value?
PIC 3: IPM (For dual/tri/quad-zone)
PIC4: Main board LED when power on and unit standby.
PIC 5: check point bottom,
press 18 times for check how many indoor units are
connected.
PIC 2, Check the wiring.
PFC (quad-zone only)