However, if you're determined to do it yourself, understanding the process is crucial:
1. Leak Detection: This is the MOST important step. Before adding any refrigerant, you *must* find and fix any leaks. A leak detector kit (using UV dye) is necessary. Add dye to the system, run the AC, then inspect all lines and components with a UV light to locate any leaks. Small leaks can be repaired with sealant, but larger leaks require professional repair or replacement of the damaged component (compressor, condenser, evaporator, lines).
2. System Vacuum: Once you've confirmed no leaks (or repaired them), you need to evacuate the system. This removes air, moisture, and any remaining refrigerant. This requires a vacuum pump capable of achieving a deep vacuum (below 500 microns) for at least 30-45 minutes.
3. Refrigerant Charge: After the vacuum, you add the correct type and amount of refrigerant. This is usually R134a in later models, but 1990 models *might* still use R12 (check your owner's manual or a reliable parts source). R12 is phased out and environmentally unfriendly. Conversion to R134a is often necessary. The amount needed is specified in your owner's manual or a repair manual specific to your vehicle. You'll need gauges to monitor pressure and temperature during the charging process. A charging manifold with gauges is essential.
4. Oil: AC systems require refrigerant oil. If you're servicing or replacing components, add the correct type and amount of oil as specified in your repair manual.
What you'll need:
* AC Refrigerant: R134a (likely for a converted system) or R12 (less likely, and environmentally damaging). Purchase the correct amount.
* AC Manifold Gauge Set: Essential for monitoring pressure and temperature.
* Vacuum Pump: To evacuate the system.
* UV Dye and Leak Detector: To find leaks.
* Refrigerant Oil (if necessary): The correct type and amount.
* Repair Manual Specific to your 1990 Ford Bronco: This provides crucial details about your system's specifications.
* Safety Glasses and Gloves: Working with refrigerants requires proper safety precautions.
Again, I strongly advise against attempting this yourself unless you have significant experience working with automotive AC systems. Improper handling of refrigerants can be dangerous, and mistakes can lead to costly repairs. The cost of a professional AC service is usually less than the potential cost of damaging the system or injuring yourself.
