Troubleshooting
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IM 972-2 • MAVERICK I ROOFTOP SYSTEMS
Troubleshooting
Troubleshooting Charts
DANGER
Disconnect all power to unit before servicing. Contactor may break only one side. Failure to shut off power can cause electrical shock resulting in personal
injury or death.
Table 18: Cooling Troubleshooting Chart
Symptom
Possible Cause
Remedy
Unit will not run
Power OFF or loose electrical connection
Check for correct voltage at compressor contactor in control box
Thermostat out of calibration-set too high
Reset
Failed contactor
Check for 24 volts at contactor coil replace if contacts are open
Blown fuses
Replace fuses
Transformer defective
Check wiring-replace transformer
High pressure control open (if provided)
Reset-also see High Head Pressure Remedy-The high pressure control
opens at 450 PSIG
Interconnecting low voltage wiring damaged
Replace thermostat wiring
Condenser fan runs,
compressor doesn’t
Loose connection
Check for correct voltage at compressor check & tighten all connections
Compressor stuck, grounded or open motor winding,
open internal overload.
Wait at least 2 hours for overload to reset. If still open, replace the
compressor.
Low voltage condition
At compressor terminals, voltage must be within 10% of rating plate volts
when unit is operating
Low voltage condition
Add start kit components
Insufficient cooling
Improperly sized unit
Recalculate load
Improper airflow
Check should be approximately 400 CFM per ton.
Incorrect refrigerant charge
Charge per procedure attached to unit service panel
Air, non-condensable or moisture in system
Recover refrigerant, evacuate & recharge, add filter drier
Incorrect voltage
At compressor terminals, voltage must be within 10% of rating plate volts
when unit is operating.
Compressor short cycles
Incorrect voltage
At compressor terminals, voltage must be ±10% of nameplate marking when
unit is operating.
Defective overload protector
Replace check for correct voltage
Refrigerant undercharge
Add refrigerant
Registers sweat
Low evaporator airflow
Increase speed of blower or reduce restriction replace air filter
High head-low vapor
pressures
Restriction in liquid line, expansion device or filter
drier
Remove or replace defective component
Flow check piston size too small
Change to correct size piston
Incorrect capillary tubes
Change coil assembly
High head-high or normal
vapor pressure Cooling mode
Dirty condenser coil
Clean coil
Refrigerant overcharge
Correct system charge
Condenser fan not running
Repair or replace
Air or non-condensable in system
Recover refrigerant, evacuate & recharge
Low vapor - cool compressor
iced evaporator coil
Defective compressor valves
Replace compressor
Incorrect capillary tubes
Replace coil assembly
Low vapor cool evaporator
coil
Low evaporator airflow
Increase speed of blower or reduce restriction replace air filter
Operating below 65°F outdoors
Add Low Ambient Kit
Moisture in system
Recover refrigerant evacuate & recharge add filter drier
High vapor pressure
Excessive load
Recheck load calculation
Defective compressor
Replace
Fluctuating head & vapor
Air or non-condensate in system
Recover refrigerant, evacuate & recharge
Gurgle or pulsing noise at
expansion device or liquid line Air or non-condensable in system
Recover refrigerant, evacuate & recharge
Summary of Contents for Maverick I
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