Defender (1993+). Manual — part 93

AIR CONDITIONING

AIR CONDITIONING BLOWER MOTOR AND CONTROL SYSTEM DIAGNOSIS

AIR

CONDITIONING

Refrigeration System Fault Diagnosis

For any refrigeration system to function properly all

components must be in good working order. The unit
cooling cycle and the relationship between air
discharge temperature and ambient temperature and

pressures at the compressor can help to

determine proper operation of the system.
The length of any cooling cycle is determined by
such factors as ambient temperature and humidity,

thermostat settng,

compressor speed

and

air

leakage into the cooled area, etc. With these factors

constant, any sudden incr ease in the length of the
cooling cycle would be indicative of abnormal
operation of the air conditioner.
The low and high side pressures at the compressor
will vary with changing

ambient temperature,

humidity, cab temperature

and

altitude.

The following conditions should be checked after
operating the system for several minutes:

1.

All high side lines and components should be
warm to the touch.

2.

All low

side lines should be cool to the touch.

3.

Inlet

and

outlet

temperatures

at

the

receiver/drier

should

be

at

the

same

temperature (warm). Any very noticeable
temperature difference indicates a blocked
receiver/drier.

4. Heavy frost on the inlet to the expansion valve

may indicate a defective valve or moisture

in

the system.

5.

With ambient humidity between 30% and
60%, compressor pressures and evaporator
air discharge temperature should fall within
the general limits given

in

the table below.

REISSUED: FEB

1993

7

AIR

CONDITIONING

AIR CONDITIONING