Emerson DH Manuel D’Utilisation

Compressor will not 

start

Power off

Check main switch, fuses or CBs and wiring

Current overload open

Reset manually

Loose electrical connections

Tighten connections

Compressor motor burned out

Check and replace compressor if defective.

Compressor will not 

operate, contactor not 

pulling in

No call for cooling

Check monitor status.

Solenoid valve not energizing

Hold screwdriver over solenoid and check for magnetic field. 

This indicates solenoid is energized.

Low pressure switch not making 

contact

Check gas pressure - manually energize low pressure 

switch.

Compressor will not 

operate, contact not 

pulling in

High pressure switch open

Reset switch. Refer to other refrigeration troubleshooting 

suggestions.

Compressor contactor 

pulled in but 

compressor will not 

operate

Blown fuse or tripped CB

Check for line voltage after fuses or CBs, and after 

contactors.

Compressor runs for 

three minutes then 

stops; contactor drops 

out. Motor operates but 

valve won't open

Low pressure switch not closing

Check for low gas pressure. Compressor is running on 

Positive Start Kit (air cooled systems only).

Solenoid not opening

Check magnetic field to see if energized.

High discharge 

pressure

Dirty condenser or drycooler fins

Clean coil

Condenser equipment not 

operating

Check operation.

High refrigerant charge

Check refrigerant charge.

Hot gas bypass valve adjusted 

improperly

Adjust properly.

Water regulating valve adjusted 

improperly

Adjust properly.

Low discharge pressure

Excessive water now through 

condenser

Adjust water regulating valve

Suction service valve partially 

closed

Open the valve.

Leaky compressor suction valves

Pump down, remove the cylinder head, examine valves and 

valve seats; replace if necessary

Worn piston rings

Replace compressor.

Faulty head pressure control 

valve or condenser fan speed 

control

Replace if defective.

Low suction pressure

Insufficient refrigerant in system

Check for leaks, repair, and add refrigerant

Dirty air filters

Change filters.

Plugged filter-drier

Replace filter.

Improper superheat adjustment

Reset expansion valve for 10-15°F

Defective expansion valve 

sensing element

Replace element

Poor air distribution

Check duct work for closed dampers. Check for underfloor 

restrictions at or near the unit.

Low condensing pressure

Check head pressure control device.

Slipping belts

Inspect and adjust