Description; Ccot A/C System; Rear Interior Roof Mounted Systems (Suburban & G-Van); System Components - GMC G Service Manual

CCOT A/C SYSTEM

The CCOT (Cycling Clutch Orifice Tube) A/C system
performs heating and cooling. Air enters the vehicle and
passes through the cooling unit (evaporator) and through
(or around) the heating unit. The system is called a "reheat"
system. The evaporator cools the air passing through the
core when the air conditioning system is in the cooling
mode.
On R/V and G-Van, a pressure sensing switch, located
near the top of the accumulator, controls compressor oper­
ation. The switch responds to pressure changes to turn the
compressor ON or OFF.
System operation:
Outside air or recirculated air enters the system and is
forced through the system by the blower. As the air passes
through the evaporator core, it receives maximum cooling if
the air conditioning controls are positioned for cooling.
From the evaporator, the air enters the heater and air
conditioner selector duct assembly where, by means of
diverter doors, it passes through or bypasses the heater
core in proportions necessary to provide the desired outlet
temperature. The air enters the vehicle through either floor
distributor duct or the instrument panel outlets.
During cooling, the air is cooled by the evaporator to
below comfort level then warmed by the heater to the
desired temperature. During "heating only" the evaporator
does not operate, and ambient air is warmed to the desired
level in the same manner.
REAR INTERIOR ROOF MOUNTED
SYSTEMS (SUBURBAN & G-VAN)
These systems operate with the front system — they do
not operate independently. However, control of the rear
blower motor speed is possible when the front system is
OFF. Rear air circulation without the refrigerant function is
possible by operating the rear blower control switch.
These self-contained units operate on inside (recircu­
lated) air. Air enters the unit and passes through the evapo­
rator core into the passenger compartment through the air
distributor duct. A portion of the front system refrigerant is
diverted to the rear unit. A three-speed blower switch con­
trols the rear interior roof mounted system.

SYSTEM COMPONENTS

THERMOSTATIC EXPANSION VALVE
Suburban and G-Van rear interior roof mounted and
motor home chassis systems use a thermostatic expansion
valve (figure ).
1

DESCRIPTION

. Power Element Thermobulb
1
. Cover
2
3. Diaphragm Back-up Plate
4. Body
5. Screen
. Orifice
6
7. Carriage Spring
Figure 1 — Thermostatic Expansion Valve
The valve consists of the power element, body, actuat­
ing pins, seat and orifice. At the high pressure liquid inlet, a
fine mesh screen prevents dirt, filings or other foreign mat­
ter from entering the valve orifice.
When the valve is connected in the system, high pres­
sure liquid refrigerant enters the valve through the screen
from the condenser and passes on to the seat and orifice
where it changes into a low pressure liquid.
The low pressure liquid leaves the valve and flows into
the evaporator core where it absorbs heat from the evapo­
rator core and changes to a low pressure vapor and leaves
the evaporator core. The power element bulb is clamped to
the low pressure vapor line just beyond the outlet of the
evaporator.
ACCUMULATOR R/V & G-VAN
The accumulator is located at the evaporator outlet. It
separates liquid retained from vapor, retains the liquid and
releases the vapor to the compressor (figure
AIR CONDITIONING 1B-3
8
J
b
k
8
9.
10
11
1 2
A.
B.
. Spring Seat
Carriage Seat
. Seat
. Actuating Pin
. Diaphragm
Inlet
Outlet
F-00190
).
2