Section IV ORGANIZATIONAL TROUBLESHOOTING

TM 5-4120-386-14

4-12. 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.

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 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 suppose to do. The following steps contain instructions for checking the

control circuit.

(1) Disconnect power from the air conditioner.

(2) Test continuity across each control in the affected circuit, using an

ohmmeter. Refer to the appropriate schematic diagram and wiring diagram

(Figures E-1 and E-2) as a guide to the connections in the circuit.

(3) 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.