Hummer H1 Service Manual page 725

11-6 Heating/Ventilation/Air Conditioning (HVAC)
A/C Servicing Precautions
There are precautions that should be followed when servicing
the A/C system. The precautions are necessary to avoid com-
ponent damage and personal injury.
• Wear eye protection when servicing the system. The re-
frigerant is under pressure and will cause injury if it
contacts the eyes.
• Never perform system repairs until after the system has
been fully discharged.
• Do not use refrigerant recovery, recycling, charging,
and evacuation/discharge servicing equipment that does
not meet SAE J–2210 standards.
• Never attempt to replace system components while the
engine is running.
• Avoid having R-134a contact the skin. The refrigerant
can cause an injury similar to frostbite. Exercise care
when handling R-134a.
• Do not allow any type of open flame near R-134a.
• Avoid breathing R-134a fumes. The refrigerant will
cause eye, nose, throat, and lung irritation.
• Never mix R-12 and R-134a in the same system. The
two refrigerants are not compatible. Mixing the two will
result in failure of the compressor and other system
components.
• Never use PAG oil from an unsealed container. The oil
will quickly absorb moisture from the air if not sealed.
Recovering (Discharging) A/C System
Refrigerant
1. Shut engine off.
2. Connect hoses from service cart J–39500-A to suction and
discharge service ports. Red hose goes to discharge side
and blue hose to suction side. Use adapter fittings J–
39500-20 and 24A if necessary. If manifold gauge set J–
39183-C is being used, connect center hose to a recovery
tank, or system.
NOTE: If both gauges indicate a zero reading, the system does
not contain any refrigerant. Add a small charge, leak test, and
make necessary repairs before proceeding.
3. Begin recovery/discharge cycle as described in service
cart instructions.
4. Recovery is complete when service cart gauges read
slightly below zero.
5. Secure the service cart as described in the manufacturer's
instructions.
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Recycling System Refrigerant
The J–39500-A service cart (from Kent Moore), will recycle
R-134a refrigerant when necessary. The original recovered re-
frigerant is moved through a combination filtration/dryer unit
built into the cart. This unit removes impurities allowing
refrigerant reuse. Follow the manufacturer's instructions care-
fully for the recycle process because incorrect use could result
in moisture in the refrigerant. The recycle process is accom-
plished automatically when the service cart is in evacuation
mode.
Evacuating the A/C System
CAUTION: Do not evacuate an A/C system that is not com-
pletely discharged. Check system pressures with a gauge set if
unsure about charge level.
The A/C system evacuation process involves applying 26-28
inches Hg to the A/C system for a minimum of 20 minutes.
The applied vacuum removes moisture. A vacuum pump built
into the service cart generates the necessary vacuum.
1. Connect service cart J–39500-A to service ports.
2. Discharge system.
3. Connect vacuum pump to center hose on manifold if
gauge set J–39183-C is being used.
4. Turn vacuum pump on, and open gauge valves.
NOTE: High side gauge should drop to zero or below. If not, a
blockage in A/C system is indicated. Deduct 1 in. vacuum from
maximum attainable reading for each 1000 ft elevation above
sea level.
5. Evacuate unit until low pressure gauge reads 26-28 in. Hg.
6. Turn vacuum pump off and allow system to sit
undisturbed for 15 min to check for vacuum leaks. If
pressure rises, diagnose system leak.
7. Continue evacuation for thirty minutes after correct gauge
reading of 26-28 in. Hg vacuum has been achieved.
8. Turn gauge valves to closed position after evacuation is
complete.
9. Turn off vacuum pump and disconnect center hose from
vacuum pump.
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