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So I did a A/C refrigerant recharge today, and want to share some lessons learned.

My A/C is blowing cool air, but it can't keep up when it's 90 degree outside.  I want to add some refrigerant to see if there are any improvements.

Before I go any further, I must warn you: if you didn't change oil yourself, or if you are very environmentally conscious, don't do this yourself.  Take it to a mechanic and tell him about special caution for hybrid A/C system.

1.  Hybrid vehicle need pure r134a refrigerant, or a refrigerant designated for hybrid vehicle use because the lubricant oil used is special hi-dielectric oil.  Don't ever use oil for conventional vehicle.  I bought A/C Pro  HYB-134A R134a refrigerant refill, 10 oz size, containing 0.5 oz oil.  If your vehicle still blow cool air, then 1 can is more than enough.

2.  You need a A/C charging hose with gauge.  Make sure the hose is long enough.  RX400H need a 24 inch long hose.

3.  Wear a latex or thin glove, ideally with long sleeve to protect your forearm from hot engine support brackets.  An old long sleeve shirt works for me.

4.  Turn car on, turn A/C on using the climate control, not the Auto setting button.  Set temperature to Max Cool.  Auto setting may or may not cut off compressor when cooling, so don't chance it.  Turn the windows down.

5.  Connect the hose to the low pressure port, following the instruction provided by the hose packaging.  Make sure the valve for the refrigerant can side is closed.

6.  Check the low pressure side pressure according to the temperature/pressure chart provided on the hose packaging.

7.  If you need to add refrigerant, shake the can well, and retract the valve's piercing pin back, so that you can screw on the can to the valve tight.  Turn valve clock        wise all the way to pierce the seal.

8.  Keep the can upright.  Open the valve by turning the handle counter-clockwise.  The refrigerant will turn into gas and be sucked into the A/C system.  Shake the can, and every 2-3 second, turn the can to 3 o'clock position to drain some of the oil into the system.

9.  Very Important: turn the valve off every 10 second to check the system pressure.    Wait a few second to see the system pressure.  When it's almost done, the pressure at the end will shot up very quickly, and lead to overfill.  Take it slow and spend your time checking the pressure with the valve closed.

10.  When the desired system pressure is achieved, turn the valve off completely.  Don't try to get to the high end of the recommended pressure range.  Remove the connector from low pressure port.  Replace the dust cover onto the port.

11.  If you overfill the system, STOP.  The compressor will cycle on, then shut off due to cutoff switch in the system.  You should do the right thing, turn off A/C, and drive to a mechanic to drain a little refrigerant out.  There are advice on the internet on how to do this by inserting a long philips head screw driver into the port, depress the valve stem to release refrigerant.  This is illegal because R134A is a greenhouse gas, even though not as bad as R12.  The valve on the low pressure port is just like your tire valve stem.  You depress the center to let the air out.

Note:  The gauge for the recharge hose is not as good as the ones used by mechanics.  It also don't have a good trigger valve, so this doesn't work as easily as the all-in-one system designed for conventional vehicle that you can buy in the auto parts store.  Don't ever use those kits because it will contaminate the hybrid A/C system with oils that will conduct electricity.

The refrigerant I used claim to seal leaks too, and it works by conditioning the rubber seals, not by plugging up the seals with goo.  People who had used it claim it worked on slow leaks over time.


It's 90 degree outside today, and my car's A/C provides a cooler breeze than before.  It's not super cold from the vent, but I heard that the system on RX400h always blends some warm air with the cold.


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Nice writeup, GW. I have done this to a vehicle, many years ago but have not needed to recharge an AC in any of my vehicles since then.


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I have a 13 year old 2005 RX330 with 120K on it and the car had AC problem as followings:

1. generally it could not keep car cool as comfortable, especially when outside temp is above 85F, when measuring temperature on four air-outlets (front panel), two on passenger side blow out air about 70F, however the two on driver side blow out air like 75F. When driving under the sun with 90F outside the inside temp is very hot. 

2. I searched online - almost everyone says it is a problem with blow motor/vent door actuator issue. However someone on this forum said she/jhe had similar symptom (with driver side cooler though) - the problem was fixed by only recharging refrigerant (sounds not making sense on surface)

3.  I decided to start with the simplest way: refill refrigerant - only DIY I could do. I had hard time to locate "low pressure port" - "" showing a video claims to be RX330 but it is not. I finally located the port at the low far back on the passenger side under the hood (need to take out the cover on passenger side first), with a black cap printed with a large "L" on it.

4. bought  a can of AC Pro (20 oz)  with a pressure gauge at a local PepBoy store ($50 but with a $20 mail-in rebate). hook up the gauge with the low pressure port according to the instruction - the reading was at very low end (not a complete "0".

5. took out the "safety spacer" on the can and screw the gauge directly on the can (piercing) and connected the end to the port, squeezing the trigger to start recharging - squeezing two seconds, shaking and reading the gauge, repeat until the reading  get to 36 lb. Disconnecting the hose and put back the original black dust cap. 

6. all four vent blow cool air - much colder than before - I have not measured if there are still differences among four vents. I don't care about that for now as far as the AC could provide a comfortable temp inside the car when outside is 91F. 

7. hope this post could help people who has similar AC problem with RX330

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