GMC 1982 Light Duty Truck Service Manual page 51

IB-8 AIR CONDITIONING
three speed blower switch (Fig. 1 B -11).
In the O F F position, the blower is inoperative;
however, refrigerant is circulating in the system if the front
system is O N . To operate the rear overhead system, simply
select the desired blower speed (L O W , MED, HI).
W hen air circulation only is desired, the rear A /C
blower motor may be operated independent of the front A /C
blower motor and without the cooling function.
DASH M O U N T E D U N IT (M O TO R H O M E CHASSIS
UNITS)
This system is self contained and is mounted below the
dash by the body manufacturer. System controls consist of
an A IR knob and T E M P knob located in the center of the
unit face plate (Fig. 1B -12).
Air Knob
Turning the A IR knob clockwise operates a three speed
( L O W -M E D -H I) blower motor.
Tem p Knob
This knob is used to control the degree of cooling
desired. Fully clockwise at C I T Y provides m axim um
cooling, while turning the knob to H I W A Y provided
adequate cooling for highway operation.
Reduced cooling could be encountered when operating
at highway speeds with the controls at the C IT Y setting.
The heater must be fully off to obtain maximum cooling.
Fig. IB-1 T-Overhead Unit Control (G Models)
Fig. IB -12-M otor Home Unit Control
CCOT SYSTEM C O M P O N E N TS
C C O T R efrigerant
refrigerant flow are shown in Fig. 1B -13. C h art 1 B-1 shows
pressure tem perature relationships of R - 12.
R efrigerant and Oil Capacities
Refrigerant and oil charge is shown in C hart 1 B-2.
H A N D L IN G REFRIG ERANT-12
Air conditioning systems contain R efrigerant-12. This
is a chemical m ixture which requires special handling
procedures to avoid personal injury.
Always wear goggles and wrap a clean cloth around
fittings, valves and connections when performing work that
involved opening the refrigerant system. Always work in a
well ventilated area and do not weld or steam clean on or
near any car installed air conditioning lines or components.
If Refrigerant-12 should come in contact with any part
of the body, flush the exposed area with cold water and
immediately seek medical help.
All Refrigerant-12 drums are shipped with a heavy
metal screw cap. The purpose of the cap is to protect the
valve and safety plug from damage. It is good practice to
replace the cap after each use of the drum for this same
reason.
If it is necessary to transport or carry any container of
R efrigerant-12 in a vehicle, do not carry it in the passenger
compartment.
If the occasion arises to fill a small R efrigerant-12
drum from a large one, never fill the drum completely.
Space should always be allowed above the liquid for
expansion.
1. Do not leave drum of R efrigerant-12 uncapped.
2. Do not carry any container of R e f r ig e r a n t-12 in
passenger compartment of car.
3. Do not subject any container of R efrigerant-12 to high
temperature.
4. Do not weld or steam clean on or near system.
5. Do not fill drum of Refrigerant-12 completely.
6. Do not discharge vapor into area where flame is
exposed.
7- Avoid breathing smoke and fumes produced by the
burning of the R efrigerant-12. Such fumes may be
hazardous.
8. One of the most im po rtant cautions concerns the
System com ponents and