Carrier 38AF - Manual (Page 5)

HEATING & COOLING
38AF
Air-Cooled Condensing Units
TROUBLESHOOTING GUIDE
COMPRESSOR DOES NOT RUN
Contactor Open
Power off — restore power.
Fuses blown — replace with correct fuses after finding
cause and correcting.
Transformer dead — replace transformer if primary
windings are receiving power.
Thermostat circuit open — check thermostat setting.
Circuit breaker tripped — check for excessive com­
pressor current draw (140% FLA maximum allowable).
Low-pressure switch open — check for refrigerant under­
charge or obstruction of indoor airflow.
High-pressure switch open — check for refrigerant over­
charge or obstruction of outdoor airflow.
Connections loose — tighten all connections.
Compressor stuck — see compressor service literature.
Compressor motor thermostat open — check for exces­
sive motor temperature.
Contactor Closed
Compressor leads loose — check connections.
Motor windings open — see compressor service
literature.
Single phasing — replace blown fuse.
COMPRESSOR CYCLES ON
HIGH-PRESSURE SWITCH
Condenser Fan On
High-pressure switch faulty — replace switch.
Airflow restricted — remove obstruction.
Air recirculating — clear airflow area.
Noncondensables in system — purge and recharge as
required.
Refrigerant overcharge — purge as required.
Line voltage incorrect — consult power company.
Refrigerant system restrictions — check or replace filter
drier, expansion valve, etc.
Condenser Fan Off
Fan slips on shaft — tighten fan hub setscrews.
Motor not running — check power and capacitor.
Motor bearings stuck — replace bearings.
Motor overload open — check overload rating. Check for
fan blade obstruction.
Motor burned out — replace motor.
COMPRESSOR CYCLES ON
LOW-PRESSURE SWITCH
Evaporator Air Fan Running
Filter drier plugged — replace filter drier.
Expansion valve power head defective — replace power
head.
Low refrigerant charge — add charge. Check low-
pressure switch setting.
Airflow Restricted
Evaporator coil iced up — check refrigerant charge.
Evaporator coil dirty — clean coil fins.
Indoor air filter dirty — clean or replace filters.
Indoor air dampers closed — check damper operation
and position.
Evaporator Air Fan Stopped
Electrical connections loose — tighten all connections.
Fan relay defective — replace relay.
Motor overload open — power supply.
Motor defective — replace motor.
Fan belt broken or slipping — replace or tighten belt.
COMPRESSOR RUNS BUT
COOLING INSUFFICIENT
Suction Pressure Low
Refrigerant charge low — add refrigerant.
Head pressure low — check refrigerant charge. Check
condenser air fan thermostat settings.
Indoor air filters dirty — clean or replace filters.
Expansion valve power head defective — replace power
head.
Evaporator coil partially iced — check low-pressure
setting.
Evaporator airflow restricted — remove obstruction.
Suction Pressure High
Compressor valves defective — see compressor service
literature.
Heat load excessive — check for open doors or windows.
Manufacturer reserves the right to discontinue, or change at any time, specifications or designs without notice and without incurring obligations.
Book|l |4 PC111 Catalog No 563-852 PrintedinUSA Form38AF-1SI Pg5 4-85 Replaces; New
For reolacement items use Carrier Soecitied Parts Tab 13a12a