Freon (refrigerant) is always added to a vehicle’s AC system through the low-pressure side, also known as the low side service port. You should never attempt to add refrigerant through the high side port.
Why Freon Goes in the Low Side
- Safety
- The low side operates at a lower pressure, making it safer to add refrigerant.
- The high side can have extremely high pressure (up to 300 PSI or more), which can cause injury or damage if you try to charge it there.
- Proper System Function
- Refrigerant enters the low side, flows through the compressor, and then moves through the rest of the system.
- Adding Freon at the low side ensures it’s properly cycled and pressurized.
How to Identify the Low-Pressure Side
- The low side service port is usually located between the evaporator and the compressor.
- It’s often marked with an “L” or labeled “Low”.
- The hose connecting to the low-pressure port is typically larger in diameter than the high-pressure hose.
- The fitting sizes are different:
- Low side port uses a quick-connect fitting, which is smaller than the high side.
Tips for Adding Freon Safely
- Always wear safety goggles and gloves.
- Ensure you’re using the correct type of refrigerant (most modern vehicles use R-134a, while newer ones use R-1234yf).
- Connect the refrigerant canister only to the low side port.
- Start the engine and turn the AC to max cooling, fan on high.
- Follow the instructions on the refrigerant kit and monitor the pressure gauge to avoid overcharging the system.
- If you’re unsure or uncomfortable, it’s always safer to have a professional mechanic handle it.
Final Answer
Freon goes in through the low-pressure side of the AC system—never the high side. This ensures safe and correct recharging of your vehicle’s air conditioning system.
Also Check:
• Does AC Leak Sealer Work?
• Does the Water Pump Affect the AC in a Car?
