This thread is for learning purposes.

I had a 2003 IS300 with an AC issue. Owner says it blows warm with AC on at max. She took it into another shop prior to me getting it. The shop supposedly evacuated and recharged the ac system with refrigerant thinking it was just low.

I get a hold of the car and try to verify the complaint. I start the engine, and turn on the AC. It blows warm air. I check the cooling fans to see if they kick on, which they do. I inspect the condenser for signs of any obvious oily leaks.

I then check for any signs of coolant leak. And also monitored the coolant temp gauge while engine got to operating temperature. No overheating here.

With an AC machine I go about evacuating and recharging the system. I was able to recover .46kg of refrigerant and charged it back with .65kg (that's what it calls for at max capacity). I put dye with oil in the system. So I start up the vehicle with AC on max full blast. And...warm air comes out (scratching my head). What the crap! I start shining my UV light to inspect for any leaks. None found.

I then hook up AC pressure gauges to monitor the low side and high side readings. With the engine running with ac on, the low side reads 70psi and high side reads 100....not good. Either the ac compressor is going bad and/or I have a bad expansion valve. I start researching online for answers...I take a gamble to replace the compressor with a new receiver dryer and recharged the system. And sure enough it started blowing cold. Vents read 30 degrees with a thermometer . Low side read 25psi and high side 175psi. Let me know what I could've done differently in the diagnosis process