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How to Identify the High and Low Sides for Freon

by Mark Robinson

Identifying the high side port and the low side port for Freon on your vehicle's air conditioning system is of the utmost importance when recharging the system. Charging the system from the wrong port may cause damage to the air conditioning system and injury to you. On 1996 and newer vehicles, identifying the ports is relatively easy, and some vehicles may feature color-coded caps to further differentiate the ports.

Step 1

Open the hood of your vehicle. Locate the silver-colored metal air conditioning plumbing on the passenger side of the vehicle.

Step 2

Locate the low side port on the line that goes from the accumulator (the round canister with two or more lines coming from it) to the compressor. The low side port will have a 13 mm quick-disconnect valve fitting with a black or blue cap on vehicles with R134a Freon, or a 7/16-inch threaded valve fitting on vehicles with R12 Freon.

Locate the high side port on the line that goes from the compressor to the condenser. The high side port will have a 16 mm quick-disconnect valve fitting with a red cap on vehicles with R134a, or a 3/8-inch threaded valve fitting on vehicles with R12.

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