Chapter 5. GENERAL MAINTENANCE INSTRUCTIONS

TM 5-4120-274-15

CHAPTER 5

GENERAL MAINTENANCE INSTRUCTIONS

Section I. SPECIAL TOOLS AND EQUIPMENT

5-2. Specially Designed Tools and Equipment

5-1. Special Tools and Equipment

No specially designed tools or equipment are re-

No special tools or equipment are required to per-

quired to perform field and depot maintenance on

form field and depot maintenance on the air con-

the air conditioners

ditioners.

Section II. TROUBLESHOOTING

Possible remedy

Probable cause

5-3. General

Faulty preasure switch -----Repair or replace pressure

This section provides information useful in diag-

switch (para 6-6 or 6-7).

nosing and correcting unsatisfactory operation or

Condenser capacity reduced Remove excess refrigerant

failure of the air conditioner or any of its compo-

by refrigerant over-

(para 5-21b).

charge accompanied by

nents. Each trouble symptom stated is followed

high discharge pressure.

by a list of probable causes. The possible remedy

Air in system----------Evacuate system (para

recommended is described opposite the probable

5-21c).

cause.

5-6. High Discharge Pressure

5-4. Compressor Will not Start

Possible remedy

Probable cause

Possible remedy

Power off--------------Check relay (para 3-37),

Condenser fan inoperative --Check condenser fan motor

fuses (para 3-33) and

(para 3-24).

wiring (para 5-22) and

Too much refrigerant ----- Remove excess refrigerant

circuit breaker (para

(para 5-21b).

3-35).

Air in system - - - - - - - - - - - Evacuate system (para 5-

Thermostat set too high -----Reset thermostat (fig.2-3).

21c) .

Loose electrical connections Tighten conections. Check

wiring and rewire if

or faulty wiring

5-7. Low Discharge Pressure

necessary. (para 6-22).

Check and replace compres-

Compressor motor burned

Possible remedy

Probable cause

sor if defective (para

out

Clean the line.

Suction line partially

5-17).

obstructed

Replace high-low pressure

High-low pressure switch

switch (para 6-6 and 6-7).

defective

Thermostat defective --- Replace thermostat (para

5-8. Flooding

3-31).

Probable cause

Possible remedy

Reset expansion valve (para

Defective or impromperly

5-5. Compressor Cycles Intermittently

6-12c).

set expansion valve

Probable cause

Possible remedy

Low pressure switch erratic Check tubing to switch, may

5-9. low Suction Pressure

in operation

be clogged. Also check

setting of switch. It may

Possible remedy

Probable cause

be toolI high.

Insufficient refrigerant in Add refrigerant (para 5-

Add refrigerant. Refer to

Insufficient refrigerant

21e.

system

in system

paragraph 5-21c.

Excessive superheat ----------- Reset expansion valve (para

Dirt or restriction in

Check and clean tubing.

6-12c.

tubing to pressure switch

5-1