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HOMESERVICE MANUALSGMC1999FORWARD CONTROL 5.7 R, AUTOMATICREPAIR AND DIAGNOSISEXTERNAL PAGESDIFFERENT CARSECTION 20 (HVAC SYSTEM - GENERAL SERVICING)CHARGING A/C SYSTEMGENERAL MOTORS
1999 GMC Forward Control 5.7 R, Automatic

General Motors

1999 GMC Forward Control 5.7 R, AutomaticSECTION General Motors
WARNING: This page does not describe the selected car, but rather 71 other vehicles, including the 1996 Saturn SW2, 1996 Saturn SW1, 1996 Saturn SL2, 1996 Saturn SL1, and 1996 Saturn SL. However, it is still accessible from the selected car via links, so may be relevant.
NOTE: Ensure LB/KG switch on the back of the ACR4 unit is set for desired refrigerant measurement unit (pounds or kilograms). Operate switch with main power off.
  1. Ensure engine is off. With ACR4 connected (from evacuation procedure), close low-side valve on ACR4 control panel. Open high-side valve on ACR4 control panel. Press CHG button and enter amount of refrigerant charge specified. When entering amount of refrigerant, ensure correct unit of weight is used. See the appropriate A/C SYSTEM SPECIFICATIONS article in this section for system capacities.
  2. After entering specified amount of refrigerant, press ENTER button. Display will blink indicating charge amount is in ACR4 memory. Press CHG button to begin charging process. ACR4 will display AUTOMATIC and show amount of refrigerant programmed for charging. Display will count down to zero until CPL is displayed indicating process is completed. If charging process is successful, go to next step. If charging process stops before system charge is complete, go to step 5).
  3. Close ACR4 high-side valve on control panel (both valves should be closed). Start engine, turn A/C system on and run until high-side and low-side gauges stabilize. Ensure high-side and low-side pressures are within specification. Ensure evaporator outlet temperature are within operating specifications.
  4. With A/C running, close high-side coupler valve and disconnect high-side Red hose from vehicle. Open both high-side and low-side valves on ACR4 control panel. Refrigerant from both hoses will be drawn into A/C system through low-side Blue hose. Close low-side coupler valve and disconnect from vehicle. Ensure proper A/C system operation.
  5. There are 2 reasons charging process will stop before system charge is complete. If refrigerant tank pressure and A/C system pressure are about the same, ACR4 will emit an audible signal and display amount of refrigerant remaining to be transferred. If this occurs, go to next step. If charging process will not complete and CHECK REFRIGERANT is displayed, there is not enough refrigerant to complete process. If this occurs, go to step 7).
  6. Close high-side valve and open low-side valve. With engine running, start A/C system and press HOLD/CONT button. Reminder of refrigerant should go into A/C system. When charging process is complete, go to step 3).
  7. If CHECK REFRIGERANT is displayed, press HOLD/CONT button to interrupt cycle. Press RESET button to reset ACR4. Recover refrigerant that has been charged into system. Fill refrigerant tank, evacuate and recharge A/C system. See EVACUATING A/C SYSTEM  and CHARGING A/C SYSTEM  . Perform the leak test procedure(s). Refer to procedures for LEAK TESTING  .
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When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

  • • You smell fuel, burning insulation, or see smoke.
  • • Brakes feel soft, pull hard to one side, or make grinding noises.
  • • The engine overheats, stalls repeatedly, or misfires under load.
  • • You are missing required tools, torque specs, or safe lifting equipment.
  • • You are not confident in the next step or safety outcome.