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Home >> Chevrolet >> 1994 >> Forward Control 7.4 N >> Repair and Diagnosis >> Heating, Ventilation & A/C (HVAC) >> General Servicing >> A/C System General Servicing >> Evacuating A/C System >> A/C System General Servicing >> R-12

A/C System General Servicing: R-12

  1. Close both valves on manifold gauge set. Connect low-side gauge hose to low-side service valve. See SERVICE VALVE LOCATIONS under SYSTEM SERVICE VALVES. Connect high-side gauge hose to evacuation pump and center hose to R-12 drum. Ensure valve on R-12 drum is closed.
  2. Fully open both valves on manifold gauge set. Operate evacuation pump until vacuum reading of at least 28-29 in. Hg on low side is obtained. If specified reading cannot be reached, check for defective evacuation pump or leak in A/C system or gauge set. Repair or replace components as necessary.
  3. Continue operating evacuation pump for 5 minutes after reaching 28-29 in. Hg. Close both valves on manifold gauge set. Stop evacuation pump. Observe low-side gauge. Any loss of vacuum indicates a system or gauge leak.
  4. If leak is indicated, charge system with 8 ounces of R-12, and perform leak testing procedure. See LEAK TESTING. Repair any leaks, and repeat evacuation procedures.
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