If your air conditioner blows lukewarm air, you can repair it by recharging the air compressor with new R134a refrigerant. Because the Mazda 3 uses R134a, you can purchase a universal recharging kit from any popular automotive part supplier and recharge the cooling system on your own. A recharge kit consists of the service hose, pressure gauge and a bottle of R134a refrigerant.
Thread the service hose onto the bottle of R134a. The service hose has a needle in the coupler that punctures the top of the bottle. Open the valve on top of the service hose to expel air out of the service hose line and then close the valve.
Remove the black cap from the "low side" valve fitting located on the compressor hose between the accumulator and the compressor. The low side valve is the only fitting on the hose and it is 13mm in diameter. The service hose will only fit onto the low side valve.
Press the other end of the service hose onto the "low side" valve and open the valve on top of the service hose.
Turn the Mazda 3 on and then turn on the air conditioner full blast. This pulls the R134a into the compressor.
Turn the valve on the service hose off when the pressure gauge reaches p.s.i..
Turn off the Mazda 3.
Disconnect the service hose from the "low side" valve and place the black cap back onto the "low side" valve.