Problem

No.

Possible Cause

Possible solution

[A] Compressor will not start, no humming

1

Line Disconnect switch open

Close to start.

2

Fuse Removed or Blown

Replace fuse.

3

Overload Protector Tripped

Refer to electrical section.

4

Defective Wiring

Repair or replace.

5

Control stock in open position

Repair or replace.

6

Control off due to cold location

Relocate control.

7

Control defective

Repair or replace.

8

Wiring improper or loose

Check wiring against diagram

9

No power to unit

Check main circuit breaker.

10

Overload protector incorrect or defective

Replace with correct one.

11

Compressor motor or mechanism defective

Repair or replace.

12

Defective Thermostat, Contactor, Transformer or Control relay.

Replace component.

13

Insufficient line voltage

Determine cause and correct.

14

Thermostat setting to high

Lower thermostat setting below room temperature.

15

High Pressure switch tripped

See problem "Excessive head pressure.

16

Low pressure switch tripped

Check for leaks, repair and recharge.

Problem

No.

Possible Cause

Possible solution

[B] Compressor will not start, hums but cycles on overload protector

1

Improperly wired

Check wiring against wiring diagram.

2

Low voltage to unit.

Call trained electrician or power company.

3

Start capacitor defective.

Determine reason and replace.

4

Relay contacts not closing.

Determine reason and replace.

5

Compressor motor has a winding open or shorted.

Replace compressor.

6

High head pressure.

Replace filter, clean coil, remove excessive refrigerant.

7

Internal mechanical trouble in compressor, low oil charge.

Correct or replace.

8

Compressor grounded

Determine reason and correct.

9

Overload protector incorrect or defective

Replace overload.

10

Compressor motor requires start assist.

Try start assist.

11

Problem

No.

Possible Cause

Possible solution

[C] Compressor starts but does not switch off of starting windings

1

Improperly wired

Check wiring against wiring diagram.

2

Low voltage on unit

Determine reason and correct.

3

Relay failing to open

Determine reason and correct.

4

Run capacitor defective

Replace

5

Start capacitor weak

Replace

6

High head pressure

Refer to (Q)

7

Compressor motor has a winding open or shorted.

Replace compressor.

Problem

No.

Possible Cause

Possible solution

[D] Compressor starts and runs but cycles on overload protector

1

Additional current passing through overload protector.

Check diagrams for items added to wrong side of protector.

2

Low voltage to unit (or unbalance if three phase).

Determine reason and correct.

3

Overload protector defective.

Replace after checking current.

4

Run capacitor defective.

Determine reason and correct.

5

High head pressure.

Check ventilation for restrictions in refrigeration system.

6

Compressor gas hot- return gas hot.

Check for leaks, add refrigerant if necessary.

7

Compressor motor has a winding shorted or partially grounded.

Replace compressor.

8

Bearings or pistons tight, low oil charge.

Correct or replace.

9

Air or non condensable gases in system

Reclaim gas, evacuate and charge to nameplate.

10

Capillary tube or strainer restricted.

Repair and replace capillary and strainer.

11

Refrigerant overcharge

Recharge to nameplate.

Problem

No.

Possible Cause

Possible solution

[E] Unit runs fine but short cycles

1

Overload protector

Refer to (D).

2

Thermostat.

Differential set to close (widen).

3

High pressure cutout due to:

(a) High head pressure.

Refer to (Q).

(b) Insufficient air or water supply.

Check air or water supply.

(c) Undercharge of refrigerant.

Fix leak, add refrigerant.

(d) Air in system.

Purge.

(e) Internal mechanical trouble in compressor.

Replace compressor.

4

Low pressure cutout due to:

(a) liquid line solenoid leaking.

Replace.

(b) Compressor discharge valves leaking.

Replace.

(c) Undercharge of refrigerant.

Fix leak, add refrigerant.

(d) Restriction in expansion valve.

Replace.

(e) Expansion valve leaking.

Replace.

5

Low voltage.

Check voltage at main panel.

6

Capacitor incorrect or defective.

Replace with correct mfd.

7

System not equalized.

Wait 5mins before restart.

8

Improper louver setting.

Deflect louver away from intake.

9

Fan motor to slow.

Replace with rated rpm and hp.

10

Unit over sized for application.

Resize according to load and size of room.

Problem

No.

Possible Cause

Possible solution

[F] Compressor tries to start when thermostat closes but cuts out on overload, after several attempts finally starts

1

Low voltage

Determine reason and correct.

2

Thermostat differential to close

Increase differential.

3

Thermostat bulb not tight contact with evaporator.

Tighten contact.

4

Defective relay (contacts pitted)

Replace.

5

Starting capacitor defective or incorrect.

Replace.

6

Slight restriction in capillary tube strainer or drier.

Replace item.

7

Air or non-condensables in system.

Purge if minor or replace contaminated refrigerant with new charge. Use high vacuum to process complete system.

8

Compressor motor requires start assist.

Try hard start kit.

9

System not equalized.

Wait 5mins before restart.

10

Discharge line restricted.

Clear discharge line.

Problem

No.

Possible Cause

Possible solution

[G] Compressor starts but immediately cuts out on overload

1

Starting relay contacts welded together.

Replace.

2

Starting capacitor defective.

Replace.

3

Low voltage.

Determine reason and correct.

Problem

No.

Possible Cause

Possible solution

[H] Unit operates long or continuously

1

Shortage of refrigerant.

Repair leak add refrigerant.

2

Control contacts stuck or frozen closed.

Clear contacts or replace control.

3

Refrigerated or air-conditioned space has excessive load or poor insulation.

Determine fault and correct.

4

System inadequate to handle load.

Replace with larger system.

5

Evaporator iced or dirty

Defrost and clean.

6

Restriction in refrigeration system.

Determine fault and correct.

7

Dirty or restricted condenser.

Clean.

8

Filter dirty.

Clean or replace.

9

Unit location to warm.

Check ventilation, relocate unit if necessary.

10

Air or non-condensable gases in system.

Refer to F7

11

Expansion valve plugged or defective

Clean or replace.

12

Fixture doors left open to long.

Caution owner or user.

13

Insufficient, defective or waterlogged insulation.

Determine fault and correct.

14

Compressor inefficient.

Replace compressor.

Problem

No.

Possible Cause

Possible solution

[I] Start capacitor open, shorted or blown

1

Relay contacts not opening properly.

Replace.

2

Prolong operation in start cycle due to:

(a) Low voltage to unit.

Determine reason and correct.

(b) Improper relay.

Replace.

(c) Starting load too high.

Correct by using pump down arrangement if necessary.

3

Excessive short cycling.

Refer to E 1,2,3 and 4.

4

Improper capacitor.

Replace.

Problem

No.

Possible Cause

Possible solution

[J] Run capacitor open, shorted or blown

1

Relay contacts not opening properly

Replace.

2

Prolong operation on start cycle due to:

(a) Low voltage to unit.

Determine reason and correct.

(b) Improper relay.

Replace.

(c) Starting load to high.

Correct by using pump-down arrangement if necessary.

3

Excessive short cycling

Refer to E 1,2,3 and 4

4

Improper capacitor

Replace.

Problem

No.

Possible Cause

Possible solution

[K] Start relay defective or burnt out

1

Line voltage too high or to low.

Determine reason and correct.

2

Incorrect relay.

Determine correct type and replace.

3

Incorrect mounting angle.

Remount relay in correct position.

4

Excessive short cycling

Refer to E 1,2,3 and 4

5

Relay being influence by loose vibrating mount.

Remount and tighten.

6

Incorrect run capacitor.

Replace capacitor.

Problem

No.

Possible Cause

Possible solution

[L] Refrigerated space temperature too high

1

Shortage of refrigerant.

Locate leak add refrigerant.

2

Restricted capillary tube strainer or drier.

Use capillary tube cleaner or replace item.

3

Control setting to high.

Reset control.

4

Expansion valve or cooling coil too small.

Replace or add surface to coil.

5

Expansion valve restricted or defective.

Replace or repair.

6

Refrigerant lines too small.

Determine correct size and replace.

7

Unit too small for application.

Determine correct size and replace.

8

Inadequate air circulation.

Improve air movement.

9

Evaporator coil plugged with ice or dirty.

Defrost and clean.

10

Evaporator oil logged.

Apply mild heat to evaporator and pump down if necessary.

11

Inefficient compressor.

Replace.

Problem

No.

Possible Cause

Possible solution

[M] Suction line frosted or sweating

1

Expansion valve passing excessive or is over sized.

Readjust valve or replace with smaller valve.

2

Expansion valve stuck open.

Clean valve or replace.

3

Evaporator fan not running.

Determine reason and correct.

4

Overcharge of refrigerant.

Reduce to correct charge.

Problem

No.

Possible Cause

Possible solution

[N] Liquid line frosted or sweating

1

Restriction in dehydrator or strainer.

Replace part.

2

Shutoff valve on receiver either partially closed or restricted.

Open valve fully.

3

Solenoid valve leaking.

Replace part.

Problem

No.

Possible Cause

Possible solution

[O] Unit noisy

1

Loose or mounting.

Locate and tighten.

2

Tubing rattle.

Reform to clear.

3

Bent fan blade causing vibration.

Replace blade.

4

Fan motor bearings worn.

Replace motor.

5

Compressor oil charge low.

Add oil.

6

Refrigerant overcharge.

Reduce refrigerant.

7

Improper unit installation.

Install properly.

8

Dirty air filter.

Clean.

Problem

No.

Possible Cause

Possible solution

[P] Evaporator freezes but defrosts while unit is running

1

Moisture

Release contaminated refrigerant. Use triple sweep with high vacuum pump for dehydration.

2

Sticking or corroded valve.

Replace.

Problem

No.

Possible Cause

Possible solution

[Q] Head pressure to high

1

Unit overcharge

Reduce refrigerant charge.

2

Air or non-condensable in system.

Refer to F7

3

Defective condenser fan motor.

Replace motor.

4

Unit location too hot.

Check ventilation, relocate unit if necessary.

5

Restriction in water cooled condenser.

Locate and correct, replace if necessary.

6

Water supply shut off.

Determine reason and correct.

7

Restriction in capillary tube, strainer or drier.

Replace part.

8

Discharge valve partially closed.

Open valve fully.

9

Restriction in discharge line.

Locate and correct.

10

High ambient temperature

Make sure area is properly ventilated or relocate unit.

11

Indoor sensor faulty

Replace.

Problem

No.

Possible Cause

Possible solution

[R] Head pressure to low

1

Insufficient refrigerant charge.

Find leak add refrigerant.

2

Leak in system.

Locate, repair and add refrigerant.

3

Unit in cold location.

Check ventilation, relocate unit if necessary.

4

Cooling water to cold.

Determine reason and correct with new connection if necessary.