Carrier 38MGR Series Service Manual

Carrier 38MGR Series Service Manual Manual pdf 31 page image

38MGR-04SM Specifications subject to change without notice. 31TROUBLESHOOTINGThis section provides the required flow charts to troubleshootproblems that may arise.NOTE: Information required in the diagnoses can be foundeither on the wiring diagrams or in the appendix.Required Tools:The following tools are needed when diagnosing the units:• Digital multimeter• Screw drivers (Phillips and straight head)• Needle-nose pliers• Refrigeration gaugesRecommended Steps1. Refer to the diagnostic hierarchy charts below and determine theproblem at hand.2. Go to the chart listed in the diagnostic hierarchy and follow thesteps in the chart for the selected problem.For the ease of service, the systems are equipped with diagnostic codedisplay LED’s on both the indoor and outdoor units. The outdoordiagnostic display is on the outdoor unit board and is limited to veryfew errors. The indoor diagnostic display is a combination of flashingLED’s on the display panel on the front of the unit. If possible alwayscheck the diagnostic codes displayed on the indoor unit first.Problems may occur that are not covered by a diagnostic code, but arecovered by the diagnostic flow charts. These problems are typical airconditioning mechanical or electrical issues that can be correctedusing standard air conditioning repair techniques.For problems requiring measurements at the control boards, note thefollowing:1. Always disconnect the main power.2. When possible check the outdoor board first.3. Start by removing the outdoor unit top cover.4. Reconnect the main power.5. Probe the outdoor board inputs and outputs with a digital multi-meter referring to the wiring diagrams.6. Connect the red probe to hot signal and the black probe to theground or negative.7. Note that some of the DC voltage signals are pulsating voltages forsignal. This pulse should be rapidly moving at all times when thereis a signal present.8. If it is necessary to check the indoor unit board, you must start bydisconnecting the main power.9. Remove the front cover of the unit and then control box cover.10. Carefully remove the indoor board from the control box. Place itface up on a plastic surface (not metal).11. Reconnect the main power and repeat steps 5, 6, and 7.12. Disconnect main power before reinstalling the board to avoid shockhazard and board damage.Outdoor Unit Digital DisplayA digital display is featured on the outdoor PCB. The LED displaysdifferent codes in the following situations:• Standby: “- -”• Compressor operation: the running frequency• Defrosting mode: “dF” or alternative displays between runningfrequency and “dF” (each appears for 0.5s)• Compressor pre-heating: “PH” or alternative displays betweenrunning frequency and “PH” (each appears for 0.5s)• Oil return process: “RO” or alternative displays between runningfrequency and “RO” (each appears for 0.5s)• Low ambient cooling mode: “LC” or alternative displays betweenrunning frequency and “LC” (each appears for 0.5s)• Forced cooling mode: the LED displays “FC” or alternativedisplays between running frequency and “FC” (each appears for0.5s)• PFC module protection occurs three times within 15 minutes: “E6”or alternates between displays of running frequency and “E6”(each appears for 0.5s)• In protection or malfunction, the LED displays an error code orprotection codeDiagnostic GuidesTable 31 — Outdoor Unit Error DisplayOUTDOOR UNIT DISPLAY LED STATUS INDOOR UNIT DISPLAYE0 Outdoor EEPROM malfunction F4E2 Communication malfunction between indoor and outdoor units E1E3 Communication malfunction between IPM board and outdoor main board — —E4 Open or short circuit of outdoor temperature sensor (T3,T4,T5,T2B) F2/F1/F3/F6E5 Voltage protection P1E6 PFC module protection — —E8 Outdoor fan speed has been out of control (Only for DC fan motor models) F5E9 Wrong wiring connection of 24K indoor unit — —F1 No A Indoor unit coil outlet temp. sensor or connector of sensor is defective — —F2 No B Indoor unit coil outlet temp. sensor or connector of sensor is defective — —F3 No C Indoor unit coil outlet temp. sensor or connector of sensor is defective — —F4 No D Indoor unit coil outlet temp. sensor or connector of sensor is defective — —F5 No E Indoor unit coil outlet temp. sensor or connector of sensor is defective — —F6 No F Indoor unit coil outlet temp. sensor or connector of sensor is defective — —P0 Temperature protection of compressor top P2P1 High pressure protection P2P2 Low pressure protection P2P3 Current protection of compressor F0P4 Temperature protection of compressor discharge — —P5 High temperature protection of condenser — —P6 IPM module protection P0LP Low ambient temperature protection — —