Although the A/C system should
not be serviced by the do-it-yourselfer, preventive maintenance can
be practiced and A/C system inspections can be performed to help
maintain the efficiency of the vehicle's A/C system. For A/C system
inspection, perform the following: The easiest and often most important
check for the air conditioning system consists of a visual inspection
of the system components. Visually inspect the air conditioning system
for refrigerant leaks, damaged compressor clutch, abnormal compressor
drive belt tension and/or condition, plugged evaporator drain tube,
blocked condenser fins, disconnected or broken wires, blown fuses,
corroded connections and poor insulation.
CHECKING FOR OIL LEAKS Refrigerant
leaks show up as oily areas on the various components because the
compressor oil is transported around the entire system along with the
refrigerant. Look for oily spots on all the hoses and lines, and
especially on the hose and tubing connections. If there are oily
deposits, the system may have a leak, and you should have it checked
by a certified air conditioning specialist.
Fig. 1: Run your hand
along the underside of all hose connections and check for leaks. If
you find a leak, have it fixed by a certified air conditioning
KEEPING THE CONDENSER CLEAR
inspect the front of the condenser for bent fins or foreign material
(dirt, bugs, leaves, etc.). If any cooling fins are bent, straighten
them carefully. You can remove any debris with a stiff bristle brush.
Fig. 1: The position of the
condenser in front of the radiator makes it particularly susceptible
to collecting debris. Periodically, remove the accumulated bugs,
leaves and other trash from the condenser.
CHECKING THE REFRIGERANT LEVEL
are two ways to check refrigerant level. On vehicles equipped with
sight glasses, checking the refrigerant level is a simple matter. Many
late model vehicles, however, do not have a sight glass, and you have
to check the temperature of the lines to determine the refrigerant
With Sight Glass
glass is normally located in the head of the receiver/drier. The
receiver/drier is not hard to locate. It's a large metal cylinder that
looks something like a fire extinguisher. Sometimes the sight glass is
located in one of the metal lines leading from the top of the
receiver/drier. Once you've found it, wipe it clean and proceed as
- With the engine and the air conditioning
system running, look for the flow of refrigerant through the sight
glass. If the air conditioner is working properly, you'll be able to
see a continuous flow of clear refrigerant through the sight glass,
with perhaps an occasional bubble at very high temperatures.
- Cycle the air conditioner on and off to make
sure what you are seeing is clear refrigerant. Since the refrigerant
is clear, it is possible to mistake a completely discharged system for
one that is fully charged. Turn the system off and watch the sight
glass. If there is refrigerant in the system, you'll see bubbles
during the off cycle. If you observe no bubbles when the system is
running, and the airflow from the unit in the vehicle is delivering cold
air, everything is OK.
- If you observe bubbles in the sight glass
while the system is operating, the system is low on refrigerant. Have
it checked by a professional.
- Oil streaks in the sight glass are an
indication of trouble. Most of the time, if you see oil in the sight
glass, it will appear as a series of streaks, although occasionally it
may be a solid stream of oil. In either case, it means that part of
the charge has been lost.
Without Sight Glass
On vehicles that are not equipped with sight glasses,
it is necessary to feel the temperature difference in the inlet and
outlet lines at the receiver/drier to gauge the refrigerant level. Use
the following procedure:
Fig. 1: Oils streaks (A),
constant bubbles (B) or foam (C) indicate there is not enough
refrigerant in the system. Occasional bubbles during the initial
operation are normal. A clear sight glass indicates a proper charge of
refrigerant or no refrigerant at all, which can be determined by the
presence of cold air at the outlets in the vehicle. If the glass is
clouded with a milky white substance, have the receiver/dryer checked
by a certified air conditioning specialist.
Fig. 3: Checking the refrigerant charge if the system has no sight glass.
- Locate the receiver/drier. It
will generally be up front near the condenser. It is shaped like a
small fire extinguisher and will always have two lines connected to
it. One line goes to the expansion valve and the other goes to the
- With the engine and the air
conditioner running, hold a line in each hand and gauge their relative
temperatures. If they are the same approximate temperatures, the
system is correctly charged.
- If the line from the expansion
valve to the receiver/drier is a lot colder than the line from the
receiver/drier to the condenser, then the system is overcharged. It
should be noted that this is an extremely rare condition.
- If the line that leads from the
receiver/drier to the condenser is a lot colder than the other line,
the system is undercharged.
- If the system is undercharged or overcharged, have it checked by a professional air conditioning mechanic.