23. Check and Maintenance of A/C System
In case of the maintenance of the vehicle A/C system, the following procedures shall be conducted:
first, listen; second, look; third, touch; and fourth, check. Its specific content is:
First, listen:
Determine the operating condition of compressor according to the sound from the compressor. For
the normal operating, only the even valve plate motion sound from the compressor can be heard. If
the slap sound can be heard, it is generally the fluid slugging sound or hammering of the coolant. If
a serious friction sound is emitted from the machine body and the clutch sometimes gives out the
friction sound and is heated, it is caused due to the excessive load of compressor, shortage of
lubrication oil or oil-break, and the slippage of the clutc. If there is a slap sound in the exterior of the
vehicle, it is caused due to either the belt loose, or the serious wear.
If the continuous impact sounds of the motion parts in the machine body can be clearly heard during
the shutdown of the machine, it is caused due to the serious wear of interior motion parts, which
results that the clearance between the shaft and bearing, piston and cylinder body, and connecting
rod and shaft is large or loose.
Second, look:
Check the cleanness of surface of the condenser first, avoid that the foreign materials and mud
acttach to the condenser, which may make an influence on the cooling effect. In general, regularly
rinse the condenser with water. CAUTION: When the condenser is rinsing, DO NOT touch the fins
to deform them. For the deformed fins, carefully correct them with a long nosed pliers.
At the air inlet of vehicle air conditioner’s evaporator, some air filters are generally installed.
Regularly check the evaporator every week, clear the foreign materials, and clean the mud from the
evaporator surface with the high-pressed air so as to avoid that the heat transfer coefficient falls
down and the A/C air is contaminated. The contents checked regularly are:
Ø Check whether there are some oil stains in all connecting sections of the A/C cooling system. If
there are some oil stains, it indicates that the leakage may occurs here. Immediately remove the
trouble A.S.A.P. For the cooling sytem, the leakage position(s) must be mainly inspected. The
mainly-inpsected positions also include: compressor shaft seal, front and rear cover plate
gasket, safety valve and etc.
Ø Check the wear, ageing, blister, crack and leaky oil stains of all hoses. Since the vehicle’s
cooling and heating systems adopt a lot of rubber hoses, these hoses may be worn due to
contact with the vehicle body during the vehicle is traveling and vibrating. The brake hoses in
the engine compartment are subject to the high temperature ageing, and easily have alligatoring
symptom, which may result that the brake fluid and coolant drain out but the moisture, air and
dust enter into the hoses to damage the compressor and all parts. So, it is very important to
regularly check these rubber hoses. If it is found that the rubber hose contact the engine,
separate the rubber hose from the engine in time, and reliably secure the rubber hose. The
rubber hose goes across the metal plate, in general, with a protective sleeve. Otherwise the
metal may cut the rubber hose.
Third, touch:
Touch the pipes and all parts of the A/C system which is working, and determine its temperature. In
the normal condition, the temperature of pipes at the high pressure end shall be 55℃ - 65℃ while
the low pressure pipes are in the low temperature state and there are some water dews on the parts,
