Service manual
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terminals, but we know by referring to the wiring diagram,
that the black wire is the common terminal, the red wire is
the start terminal and the white wire is the run terminal.
Notice that when we are using an ohm meter, the power must
be turned off. It is also important to disconnect all wires
from a conductor being checked with an ohm meter to
prevent any chance of feedback.
An Ammeter is an essential instrument to have and use, and
is a real bargain because it is three instruments in one.
3. Volt Meter And Its Use
A volt meter measures the amount of electrical pressure in an
electrical conductor just as a tire gauge measures the amount
of air pressure in an automobile tire. If we attach one volt
meter probe to the hot line and the other probe to the neutral
line of a standard circuit, the meter reading will be the
electromotive (electron moving) force or pressure difference
between the two lines. This is the amount of pressure we
have available to push electricity (electrons) through the light
bulbs to make the motors turn, etc. In the above example, we
should find approximately 115 volts (domestic USA models)
or units of electrical pressure. Remember, a volt meter
always registers the voltage pressure difference between two
points.
CAUTION
A volt meter is used on live circuits so use
extreme care. THINK SAFETY!
4. Refrigerant Recovery Equipment
The Environmental Protection Agency has implemented strict
regulations on refrigerant handling and refrigerant recovery
equipment.
Check with your local EPA office regarding what type of
certification you must have to open or work on the refrigerant
sealed system.
In accordance to the Clean Air Act passed in 1980:
1. There shall be no venting of refrigerant into the
atmosphere after July 1, 1992.
2. All recovery equipment must meet EPA standards
(check with your local office).
3. Technician Certification deadline was
November 14, 1993.
5. Charging Equipment
The amount of charge in any refrigerant system must be kept
accurate to within a fraction of an ounce to prevent damage to
the compressor and insure proper performance. Systems must
not be charged to a certain amperage pull. They must not be
charged to certain suction line temperature.
The recommended field instrument for charging the right
amount of R-22 into the system is either:
1. An electronic scale made especially for charging a/c
systems of critical charge. (Note: The charge must
not be weighed in with inaccurate bathroom scales,
or,
2. A Dial-A-Charge of 5 lb. capacity. Do not use the
Dial-A-Charge 10 lb. capacity or any other charging
cylinder on which the graduations of the scale are
such that the instrument cannot be read accurately.
Follow the charging cylinder manufacturer’s instructions
carefully.
6. Vacuum Pump
It has long been recognized that the worst enemy of a
refrigeration system is water. R-22 (and other refrigerants)
will break down and change to strong acids at elevated
temperatures in the presence of water. The greater the
concentration of water, the lower the temperature at which the
refrigerant will break down. The only way to remove the
water from a system to a satisfactory level is to vaporize it and
draw it out of the system with a vacuum pump.
A good quality vacuum pump is one of the finest pieces of
machinery there is, so it deserves the best of care. Keep it
clean and protected. The oil should be changed each time
before it is used.
7. Vacuum Gauge
To go with a good vacuum pump, a good quality vacuum
gauge must be used. The pump may not pump a good vacuum
due to contamination of the oil. Also a leak in the system or
service hoses may prevent a deep vacuum from being reached.
The length of time that it takes for the pump to evacuate a
system will vary with the amount of moisture and air in the
system. The gauge will not show a deep vacuum (under 200
microns) until all of the water has been boiled out. Also, if a
system has even a very small leak, it cannot be properly
evacuated. So a good gauge will indicate whether or not we
have a dry system with no leaks. The vacuum gauge to get is a
thermistor type. Remember, when you buy a gauge, it must be
read accurately at 200 microns and below.
8. Leak Detectors
It is strongly recommended that a Service Technician carry
two types of leak detectors at all times.