21/25
55208033-08
FAULT FINDING
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 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
Heronhill - for all your Marstair requirements
Tel: 01823 665660
www.heronhill.co.uk
Fax: 018123 665807