Testing The Refrigerant System; Leak Testing The Refrigerant System; Pressure Sensing Switch; Compressor Cut-Out Switches - GMC G Service Manual

TESTING THE
REFRIGERANT SYSTEM
If a malfunction is suspected due to abnormal system
pressures, check for the following:
1. Plugging in outer radiator and condenser cores.
Check between the condenser and radiator.
2. Restrictions or kinks in evaporator core or condenser
core, hoses, tubes, etc.
3. Refrigerant leaks.
4. Leaks or restrictions in air ducts. Air restriction may
indicate a plugged (or partially plugged) evaporator
core.
5. Compressor clutch slippage.
. Improper drive belt tension.
6
7. Plugged accumulator, orifice (expansion tube) or
plugged suction inlet screen (A
. Moisture in the refrigerant system.
8
LEAK TESTING THE
REFRIGERANT SYSTEM
J 29547 — AUTOBALANCE REFRIGERANT LEAK
DETECTOR
Electronic circuitry detects refrigerant or halogen gas
leaks as small as 1/2 oz. per year. J 29547 features a slide-
type on-off switch that also resets the unit in contaminated
areas.
Leaks are detected through a change in signal tone and
flashing Light Emitting Diode (LED) built into the 45.7 cm
(18-inch) flexible probe (figure 12). A 102 cm (40-inch)
coiled extension permits detection in hard-to-reach places.
A green LED battery life monitor glows to indicate suffi­
cient operating voltage when the unit is on. Field service is
possible with replacement tips, filters and a sensing ele­
ment which can be cleaned with common solvent.

PRESSURE SENSING SWITCH

A pressure sensing switch located near the top of the
accumulator, cycles the compressor clutch on R/V and G
series systems. The switch also shuts off the compressor
clutch when there is a low refrigerant charge.
The A/C system does not have to be discharged to
replace the switch. The pressure switch fitting is equipped
with a schrader-type valve.
compressor).
6
(O-ring), and tighten switch to 10 N»m (90 in. lbs.).
cut-out switches. If the engine temperature gets too high
(usually during idle after high loading conditions), these
switches shut off the A/C compressor, reducing the load on
the engine and preventing engine overheating.
thermostat housing. When the coolant in the top tank
reaches 124° C (255° F), the switch shuts off the compres­
sor. When the coolant temperature drops below 116° C
(240° F), the switch allows the compressor to reengage.
located in the back of the A/C compressor. This switch
senses compressor outlet pressure. When the pressure
exceeds 2,827-3,103 kPa (410-450 psi), the compressor is
shut off until the pressure drops below 1,448-1,724 kPa
(210-250 psi).
AIR CONDITIONING IB-11
Figure 12 — Leak Checking the System
Using J 29547
When replacing the switch, use a new oiled seal
Refer to the following trouble shooting charts:
1. Insufficient Cooling Diagnosis (figures 13,14, and 15,
16 and 17).
. Compressor Diagnosis (figure 18).
2
COMPRESSOR CUT-OUT
SWITCHES
The 7.4L engine (L19) is equipped with two compressor
One switch, a coolant cut-out switch, is located in the
The second switch, the head pressure cut-out switch, is