UNIT TROUBLESHOOTING - TM-9-4120-425-14-P0075

TM 9-4120-425-14&P

UNIT TROUBLESHOOTING

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THIS WORK PACKAGE COVERS:

Air Conditioner Fails To Operate, Insufficient Cooling, Fan Motor Fails To Operate, Compressor Will Not

Start, Insufficient Heating

INITIAL SETUP:

Maintenance Level

Reference

Unit

WP 0009-00, Malfunction/Symptom Index

General

This section provides information useful in diagnosing and correcting unsatisfactory operation or failure of the air

conditioner. Each malfunction is followed by a list of probable causes and actions to take to remedy the malfunction.

You should perform the tests/inspections and corrective actions in the order listed. Refer to the malfunction/symptom

index (WP 0009-00) as a quick reference index for troubleshooting procedures.

This manual cannot list all malfunctions that may occur nor all tests or inspections and corrective actions. If a

malfunction is not listed or is not corrected by listed corrective actions, notify your supervisor.

Control Circuit

The cause of a system's failure to operate can be greatly narrowed if the control that caused the failure can be isolated. It

is the function of safety devices to open the circuit under certain conditions; therefore, additional checking may be

required to determine whether the safety device is open because it is bad or because it is doing what it is supposed to do.

The following steps contain instructions for checking the control circuit.

Disconnect power from the air conditioner and position Mode Selector rotary switch to "OFF".

Test continuity across each control in the affected circuit, using an ohmmeter. Refer to the appropriate schematic

diagram (WP 0122-00) as a guide to the connections in the circuit.

Replace defective parts.

Safety Devices

When testing the control circuit and other equipment, you must take into consideration the fact that open safety devices

may not be bad. It may be normal for the device to be open under the existing conditions, or it may indicate trouble

elsewhere in the air conditioner.

WARNING

Refrigerant under pressure is used in the operation of this equipment.

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