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GENERAL FAULT FINDING (ALL SYSTEMS)
CONDITION POSSIBLE CAUSE ACTION
A Indoor fan motor will not run No electric supply at socket or switched fuse box
Check fuse rating and replace if necessary. Check for
loose electrical connections
Unit wiring fault Check wiring and connections
Fan motor capacitor defective Replace if faulty
Fan motor defective Replace if faulty
Internal fuse blown Clear fault and replace fuse
B Inadequate cooling or heating Dirty evaporator fins/filter Clean if blocked
Evaporator motor not running As in section A
Refrigerant shortage or excess
Check for leaks. Repair, evacuate and recharge or
check for high head pressure and recover refrigerant
if necessary
Faulty or incorrectly set thermostat Replace if faulty
Dirty condenser Clean if necessary
Faulty compressor Replace
LP cutout circuit open (if LP fitted) Check as refrigerant shortage or excess
C Compressor and outdoor fan motor LP cutout circuit open (if LP fitted) Check as above
will not run
No electric supply at socket or switch fuse box
Check fuse rating and replace if necessary. Check for
loose electrical connection.
Unit wiring fault Check wiring and connections
Capacitor, thermostat, relay or overload defective Replace if faulty
Compressor failure Replace if faulty
Controls not set properly Check and rectify
Off cycle delay operating If applicable, wait 3 minutes
High condensate level detected See G
Compressor runs, outdoor fan doesn’t Pressure at sensor < 200psig Normal: or unit may be short of gas
D System runs for long periods and will Unit underrated for conditioned area Check heat load against capacity
not cycle Thermostat not operating correctly Check wiring, position of phial and operation
Refrigerant shortage
Check for leaks. Recover, repair, evacuate and
recharge
Indoor coil dry or partly sweating Dirty condenser Clean fins if necessary
E Indoor coil frosting Refrigerant shortage
Check for leaks. Recover, repair, evacuate and
recharge
Dirty evaporator fins/filter Clean if blocked
Running in cool ambient without a head pressure
controller
Fit head pressure controller
If room temperature is also low Thermostat set too low or cooling permanently Reset or replace
F Noisy unit Fan fouling cowl (outdoor unit) Realign fan
Worn motor bearing Replace motor
Casing or piping vibration Check cause and rectify
Loose parts or mounting Find and tighten
Bent fan blade Replace fan
G Water leaking from unit Blocked drain or filter Clear obstruction
Units with lift pump or condensate pump No supply to pump or loose connection Secure the supply
Pumping slowly Check drain pipes; if clear, replace pump
Pump windings shorted Replace pump
Fouled sensor (5m condensate pump only) Clean sensor
H Pump always runs Faulty sensor or pcb Replace sensor or pcb
I No heating Controls not set for heating Reset
Unit wiring fault Check wiring and connections
Dirty evaporator fins/filter Clean
Faulty thermostat Check for signal; replace if faulty
Faulty heater element Replace
Faulty heater cutout Replace, (check for short circuiting)
Reversing valve jammed A light tap may free it; preferably replace
J
Overload tripped on three phase
units
High voltage supply Max rated voltage 254v -- check supply
Compressor failure Replace
Fuses blown
Replace fuses and investigate reason for fuses
blowing
K Outdoor unit does not operate No mains supply
Check fuse rating and replace. Check for loose
electrical connections
Supply below 187V Check supply
Isolator switched off Turn isolator on
Internal fuse blown Check fuse and replace
Data wires disconnected Reconnect data wires
No command signal Check indoor unit
Off cycle delay operating Wait in cooling for 3 minutes
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