14-27.1. AIR-CONDITIONING SYSTEM SERVICING (R-134a) (Cont'd)
Never mix R-134a and R-12 refrigerants. They are incompatible
and will cause severe damage to system components if mixed.
Whenever any air-conditioning vapor system component needs
replacement, the system must be discharged, flushed, and a
The following procedure applies to vehicles with R-134a
a. Manifold Gauge Set Installation
Turn high-pressure gauge valve (2) and low-pressure gauge valve (1) on manifold gauge set (3)
clockwise to seated (closed) positions.
Remove two caps (10) from service valves (11) and turn service valve shafts (9) counterclockwise to
Remove two caps (6) from service ports (7) and (8).
Ensure hand valves on manifold gauge are in closed position
during connection and hoses are clear of any moving parts in
engine compartment. Injury to personnel or damage to equipment
Connect low-pressure gauge hose (5) on manifold gauge set (3) to suction (low side) service port (7).
Connect high-pressure gauge hose (4) on manifold gauge set (3) to discharge (high side) service port (8).
Hang manifold gauge set (3) so hoses (4) and (5) are well away from moving engine parts.
Turn service valve shafts (9) to mid-seated position.
Do not perform step 8 if system is already evacuated. High- and
low-pressure hoses must be purged with R-134a for charging
purposes (refer to task f.).
Slightly loosen low-pressure gauge hose (5) and high-pressure gauge hose (4) at manifold gauge set (3)
to purge air from hoses, then tighten.