Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
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HOMESERVICE MANUALSGMC1999FORWARD CONTROL 5.7 R, AUTOMATICREPAIR AND DIAGNOSISEXTERNAL PAGESDIFFERENT CARSECTION 20 (HVAC SYSTEM - GENERAL SERVICING)EVACUATING 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.
- To ensure ACR4 tank contains sufficient refrigerant to recharge system, press RESET and ENTER buttons at the same time to enter diagnostic mode. When in diagnostic mode, press "7" button. If less than 8 lbs. (3.6 kg) is displayed add new refrigerant to tank.
- Connect high-side and low-side hoses to vehicle A/C system and open both high-side (Blue) and low-side (Red) valves on ACR4 control panel. Open both Red LIQUID and Blue GAS (vapor) valves on tank.
- ARC4 will begin an automatic programmed evacuation time. If a longer evacuation time is desired, enter longer time and press ENTER button. Display will begin to blink, indicating data input. Press VACUUM button to activate vacuum pump. Time display will count down from 15 minutes to zero, indicating operating time remaining. RECYCLE will display 5 seconds after pump activates and will continue until process is complete.NOTE: A pressure release sound may be heard as non condensable gases, such as air, are automatically vented from tank during recycling process. MOISTURE INDICATOR must be Green during recycling verifying refrigerant moisture content is within specification. Yellow indicates a wet condition requiring a ACR4 filter/drier cartridge replacement.
- After vacuum pump has been running for about 3 minutes (12 minutes run time remaining), press HOLD/CONT button to stop vacuum pump. If vacuum pressure is zero, there is a system leak. Repair leak and begin evacuation procedure again. If vacuum pressure is 27-30 in. Hg., close low-side and high-side valves and watch vacuum pressure for a possible leak. If vacuum is not maintained, find and replace A/C system leak.
- If vacuum pressure is maintained at 27-30 in. Hg., open high-side and low-side valve and press HOLD/CONT button to restart vacuum pump. When vacuum sequence is completed, CPL will be displayed indicating evacuation is complete.
NOTE:
Every 10 hours of operation vacuum pump oil must be changed. If OIL warning light flashes during operation, press CONT button and change oil before next operation.
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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.