However, if you're determined to attempt it yourself, understand the risks and proceed with extreme caution. Here's a *general* outline of the process, but this is NOT a complete or safe guide:
1. Safety First:
* Wear safety glasses: Refrigerant can cause eye damage.
* Work in a well-ventilated area: Refrigerant is harmful if inhaled.
* Use proper tools: You'll need gauges to measure pressure, a refrigerant recovery/recycling machine, and possibly a vacuum pump. Improper tools will damage your system.
2. Identify the Refrigerant Type: Your 2003 GMC Envoy likely uses R-134a refrigerant. Verify this in your owner's manual before proceeding. Using the wrong refrigerant can severely damage your system.
3. Locate Service Ports: These are usually low-side (usually blue) and high-side (usually red) ports on the AC lines. They are usually capped.
4. Evacuate the System: This is CRITICAL. A vacuum pump removes air and moisture from the system. Moisture is extremely damaging to the AC compressor. This step requires a vacuum pump and a gauge to monitor the vacuum level.
5. Recharge the System: Using your refrigerant recovery/recycling machine, charge the system according to the manufacturer's specifications found in your owner's manual or a reliable online source for your specific vehicle. The machine will measure the pressure and the amount of refrigerant added. Do not just add refrigerant without first evacuating the system.
6. Check for Leaks: After recharging, use a leak detection kit to check for any leaks in the system. Even a small leak will render your recharge ineffective.
Necessary Tools (and the reason this is best left to professionals):
* Refrigerant recovery/recycling machine: This is the most important tool. It recovers the old refrigerant, recycles it (if possible), and allows for precise recharging.
* Vacuum pump: To remove air and moisture from the system before recharging.
* Manifold gauge set: To monitor pressures during evacuation and charging.
* Leak detection kit: To find any leaks in the system.
* Refrigerant (R-134a): Buy the correct amount based on your vehicle's specifications.
Again, I strongly advise against attempting this yourself unless you have extensive experience with automotive AC systems and the proper tools. The risks of damaging your system are substantial. The cost of a professional recharge will likely be far less than the cost of repairing a damaged compressor or other AC components caused by improper handling.
