Carrier 38AC - Manual (Page 6)

Compressor Runs (Low Suction and Low Head
Pressure; Outdoor Fan Running)
Suction valve partially closed — open valve.
Filter-drier restricted — replace filter-drier.
Expansion valve restricted or clogged — replace
expansion valve and filter-drier.
Indoor check valve defective — replace check
valve.
System undercharged — add refrigerant; see
charging chart.
Outdoor coil dirty — clean coil.
Outdoor coil heavily frosted — check defrost
circuit electrical connections. Check physical
contact between defrost thermostat sensing
bulb and liquid line. Replace defrost relay,
defrost thermostat, defrost timer or reversing
valve.
Compressor Runs (High Suction Pressure and Low
Superheat)
Compressor flooding — check position and/or
seal of outdoor check valve. Check expansion
valve operation.
Outdoor check valve leaking or backwards —
replace check valve.
Outdoor expansion valve stuck open — replace
expansion valve.
Electric Resistance Strip Heater Not Operating
Outdoor thermostat defective — check capillary
tubing for pinches Check to be sure sensing
bulb senses true outdoor temperature.
Outdoor thermostat set too low - reset
thermostat.
Heater relay or contactor defective — replace
relay or contactor
Fuses blown — replace fuses
Fuse link open — replace fuse link.
Heater element broken — replace element.
Overtemperature thermostat defective or open
— replace overtemperature thermostat or check
air flow over heater element enclosure.
Defective room thermostat second stage —
replace thermostat assembly.
COOLING CYCLE (INSUFFICIENT COOLING)
Compressor Cycles on High Pressure Switch
Outdoor air restricted or recirculating — clean
debris from coils or fans Remove shrubbery or
foliage. Install baffles to improve air flow.
Outdoor fan stopped — check fan power,
operation of fan relay or defrost relay. Replace
defective or damaged parts.
Compressor Cycles on Low Pressure Switch
(Indoor Fan Stopped)
Indoor fan motor or relay defective — replace
motor or relay. Check motor protection.
Electrical connections loose — check and
tighten all connections.
Fan belt sUps or is broken — adjust belt tension
or replace belt.
Compressor Cycles on Low Pressure Switch
(Indoor Fan Running)
Indoor air coil iced up — check expansion valve
and refrigerant charge.
Refrigerant charge low — add charge; see
charging chart.
Expansion valve closed or plugged ^ clean or
replace expansion valve.
Filter-drier restricted — replace filter-drier.
Outdoor check valve restricted or backwards —
replace check valve.
Compressor Runs (Low Suction Pressure)
Coil frosted — clean or replace air filter.
Ducts restricted — clean ductwork.
Dampers partially closed — adjust dampers
correctly.
Refrigerant charge low — add charge; see
charging chart.
Liquid line restricted — replace filter-drier if
restricted. Replace expansion valve power
element if defective. Replace outdoor check
valve if stuck.
Compressor Runs
(High Suction; Low Head Pressure)
Reversing valve hung up or leaks internally —
replace reversing valve.
Compressor valves or head gasket defective —
replace valves or gasket.
Compressor Runs
(High Suction Pressure; Low Superheat)
Compressor flooding — check position and/or
seal of indoor check valve. Check expansion
valve operation.
Indoor expansion valve stuck open — replace
expansion valve.
Manufacturer reserves the right to change any product specifications without notice.
C A R R I E R A I R C O N D I T I O N I N G C O M P A N Y • S Y R A C U S E , N E W Y O R K
Tab 12 Form 38AC-2SS Supersedes 38AC-1SS Printed in U S A. 4-69 Codes B and MS Catalog No 533-806