How do I Locate a Low Side Service Port?by Richard Ristow
A low-side service port is part of an automobile's air conditioning system. It can be found inside a vehicle's engine compartment on the air conditioner's metal pipes. The port is intended for recharging the Freon levels within the air conditioning system.
How To Find the Low Side Port
Open and prop the hood over the automobile's engine compartment. Look towards the center of the engine to find the air conditioner's metal pipes. These pipes will connect a compressor to a drier and evaporator. The low-side port will be on one of the air conditioner's pipes and it often uses a black or blue dust cap.
High Side Versus Low Side Ports
Both ports are located on the air conditioner's metal pipes. The low-side port, like the name suggests, is lower on the pipes towards the front of the engine. While the low-side port is intended for recharging Freon, the high-side port is used for maintaining an air conditioner's internal pressure.
Freon Recharging Kits
Vehicle air conditioners use either R12 or R134a Freon, depending on their year of manufacture. The Environmental Protection agency has phased out R12, and vehicles manufactured 1984 and later are required to use R134a. Vehicles must use only one type of Freon. Mixing the two will cause damage; R12 should never be added to a R134a system.
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