A/C System Refrigerant And Capacity - Hummer H1 Service Manual

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A/C SYSTEM REFRIGERANT AND CAPACITY

The required refrigerant for Hummer A/C systems is R-134a.
This is a colorless, odorless non-flammable, liquefied gas.
A special refrigerant oil is required for use with R-134a which
is polyalkaline glycol (PAG). This is the only oil that can be
used with R-134a refrigerant. More specifically, General Mo-
tors® PAG oil must be used with the A/C compressor on the
HUMMER.
CAUTION: R12 and R-134a refrigerants are not compatible.
They must never be intermixed. Unsatisfactory cooling, rapid
sludge buildup, and compressor failure will result. System re-
frigerant capacity is:
3 lbs 2 oz
R-134a Refrigerant Precautions
To avoid product damage and personal injury, the following
precautions should be followed when working with R-134a re-
frigerant.
• Wear safety goggles when servicing the A/C system as
the refrigerant is under pressure.
• Never mix R-134a and R-12 refrigerants. They are in-
compatible and will cause severe damage to system
components if mixed.
• Use an approved A/C service cart such as the Kent
Moore J–39500-A to service the system. Recommended
service carts are those capable of evacuation, recovery,
recycling, and recharging of systems with R-134a.
• The only compressor lubricant oil that can used with
this system is General Motors PAG oil. Use of substi-
tutes will result in lubricant failure.
• Lubricate system fittings and o-rings with a 525 viscos-
ity refrigerant oil for leak proof connections.
• Do not heat containers of R-134a above 125° F (52° C).
• Never puncture or incinerate containers of R-134a.
• Avoid breathing R-134a. The gas will irritate the nose,
throat, and lungs. In addition, because R-134a is heavier
than air, it can displace oxygen in a confined and a
poorly ventilated area. Be sure the work area is properly
ventilated in case of accidental release into the nearby
atmosphere.
A/C System Pressure Test
System pressure testing involves measuring suction and dis-
charge pressures with manifold gauge set J–39183-C, or with
the gauges contained in A/C service cart J–39500-A. One
gauge is for high side (discharge) pressures and one for low
side (suction) pressures. The gauges allow pressures to be
checked while the system is in operation.
On models where access to the service ports is limited, coupler
adapters J–39500-20A and J–39500-24A, will make gauge
hose connection easier.
05745159
Heating/Ventilation/Air Conditioning (HVAC)
Pressure Test Procedure
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8.
BLUE SUCTION
(LOW SIDE) HOSE
Connect gauge hoses on service cart J–39500-A to service
ports on suction and discharge lines (Figure 11-4). Red
hose goes to high side (discharge) port and blue hose to
low side (suction) port.
Note pressure with engine not running and A/C system
inoperative. There should be approximately 50 psi to 70
psi in the system. If pressure is lower or zero, a system
leak exists. Add a small charge to the system. Then leak
test and repair as necessary before proceeding.
Start and run engine at 1200 rpm.
Set A/C controls to maximum cooling and set blower to
highest speed.
Verify that compressor clutch engages. If clutch fails to
engage, diagnose and repair before proceeding
Record low and high side pressures. Depending on engine
speed and shop ambient temperature, low side pressure
will range from 18 to 35 psi (124 to 241 kPa) and high side
pressure from 176 to 320 psi. Ambient temperatures will
affect refrigerant pressures in the system. On cool days,
pressures are lower; on hot days pressures are higher.
Refer to system pressure comparison chart at end of this
section.
If low and high side pressures are OK, check air
temperature at outlet duct closest to evaporator with
thermometer J–6742-03. Temperature should range from
33°F to 45°F depending on ambient temperature. Be sure
thermometer tip is inserted into duct to a depth of at least
one inch (25 mm).
If low and high side pressures are incorrect and air duct
outlet temperatures are greater than specified, refer to
pressure test diagnosis charts for potential causes.
COMPRESSOR
Figure 11-4: Service Hose Connections at
Compressor
11-5
RED DISCHARGE
(HIGH SIDE) HOSE
00-S11-002