Toyota Corolla Repair Manual: On–vehicle inspection

Toyota Corolla Repair Manual / Heater & air conditioner / Refrigerant / On–vehicle inspection

1. Inspect refrigerant pressure with manifold gauge set

this is a method in witch the trouble is located by using a manifold gauge set. Read the manifold gauge pressure when the these conditions are established.
Test conditions:

temperature at the air inlet with the switch set at recirc is 30 – 35 °c (86 – 95 °f)
engine running at 1500 rpm
blower speed control switch at ”hi” position
temperature control dial at ”cool” position a/c switch on
fully open doors

Normally functioning refrigeration system.
Gauge reading:
low pressure side:
0.15 – 0.25 Mpa (1.5 – 2.5 Kgf/cm2) high pressure side:
1.37 – 1.57 Mpa (14 – 16 kgf/cm2)

Moisture present in refrigeration system.

Symptom

Probable cause

Diagnosis

Remedy

During operation, pressure on low pressure side sometimes become a vacuum and sometime normal

Moisture in refrigerating system freezes at expansion valve orifice causing a temporary stop of cycle, however, when it melts, normal state is restored.

Drier in oversaturected state
moisture in refrigerating system freezes at expansion valve orifice and blocks circulation of refrigerant

Replace condenser
remove moisture in cycle by repeatedly evacuating air
supply proper amount of new refrigerant

Insufficient cooling

Symptom

Probable cause

Diagnosis

Corrective actions

Pressure low on both low and high pressure sides
insufficient cooling performance

Gas leakage in refrigeration system

Insufficient refrigerant
refrigerant leaking

Check for gas leakage and repair if necessary
supply proper amount of new refrigerant
if indicated pressure value is close to a 0 when connected to gauge, create the vacuum after inspecting and repairing location of leak

Poor circulation of refrigerant

Symptom

Probable cause

Diagnosis

Corrective actions

Pressure low on both low and high pressure sides
frost on pipe from condenser to unit

Refrigerant flow obstructed by dirt in receiver

Receiver clogged

Replace condenser

Refrigerant does not circulate

Symptom

Probable cause

Diagnosis

Corrective actions

Vacuum indicated on low pressure side, very low pressure indicated on high pressure side
frost or dew seen on piping before and after receiver/ drier or expansion valve

Refrigerant flow obstructed by moisture or dirt in refrigerating system
refrigerant flow obstructed by gas leaked from expansion valve

Refrigerant does not circulate

Check expansion valve
clean out dirt in expansion valve by air blowing
replace condenser
evaporate air and supply proper amount of new refrigerant.
For gas leakage from expansion valve, replace expansion valve

Refrigerant overcharged or insufficient cooling of condenser

Symptom

Probable cause

Diagnosis

Corrective actions

Pressure too high on both low and high pressure sides

Unable to develop sufficient performance due to excessive use of refrigerating system
insufficient cooling of condenser

Excessive refrigerant in cycle"too much refrigerant supplied
condenser cooling insufficient"condenser fins clogged at cooling fan

Clean condenser
check cooling fan with cooling fan motor operation
if (1) and (2) are in normal state, check amount of refrigerant and supply proper amount of refrigerant

Air present in refrigeration system

Symptom

Probable cause

Diagnosis

Corrective actions

Pressure too high on both low and high pressure sides
the low pressure piping too hot to the touch

Air entered in refrigerating system

Air present in refrigerating system
insufficient vacuum purging

Check compressor oil to see if it is see if it is dirty or insufficient
evacuate air and supply new refrigerant

Expansion valve improperly

Symptom

Probable cause

Diagnosis

Corrective actions

Pressure too high on both low and high pressure sides
frost or large amount of dew on piping on low pressure side

Trouble in expansion valve

Excessive refrigerant in low pressure piping
expansion valve opened too wide

Check expansion valve

Defective compression compressor

Symptom

Probable cause

Diagnosis

Corrective actions

Pressure too high on low high pressure sides
pressure too low to on high pressure side

Internal leak in compressor

Compression failure
leakage from valve damaged or broken sliding parts

Repair or replace compressor

Gauge readings (reference)

Replacement

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