Service DiagnosisDomestic Air Conditioner738.4.7 The communication fault between IPM and outdoor PCBOutdoor display LED1 flash 4 timesMethod of Communication is detected by checking the IPM module and the outdoor PCBMalfunctionDetectionMalfunction Ŷ The outdoor PCB broken leads to communication faultDecision Ŷ The IPM module broken leads to communication faultConditionsSupposed Ŷ The outdoor PCB is brokenCauses Ŷ The IPM module is brokenŶ Communication wiring disconnectedTroubleshooting * Caution Be sure to turn off power switch before connect or disconnect connector, orelse parts damage may be occurred.1) Check whether Terminal CN23 and CN24 on the outdoor mainboardCN10 and CN11 on IPM module2) Check whether the connected wire between IPM and outdoorAre they good?Electrify the machine again and turn iton, Check whether the voltage between1 and 2 of Terminal CN23 is aboutDC5V, Check whether the voltagebetween2 and 3 of Terminal CN23 isabout DC15V,Replace the outdoor mainboard with a new oneReplace the outdoor IPM modulewith a new one.YESNONOYESMalfunction unsolved1) Pull out and reinsert the terminals.2) Replace connected wire