Sorry if this is already post here. I hope this provides some good information for folks with the same problem I had.

I had the A/C Condenser replaced in my 2004 Accord LX 4-Door 2.4L DOHC by the dealership around Christmas 2018. By March 19, the system wasn't cooling. I was on the fence with regard to taking it back in (long story), so I added some 134a (got it to about 40 pounds at 90 degrees ambient, if you believe the gauge). It was starting to fade again recently, so I decided to buy a Halogen Leak Detector from Amazon ... about $30. I ran it around the engine compartment, and it indicated a leak in the high side valve. Made sense, since it made a bit of a "opening a soda can" sound when I unscrewed the cap. While researching how to replace A/C valve cores, I came across a tool that allows you to remove them without discharging the system. I gave it a go, and it worked!

What I found out that might help:

The high side valve contains a Standard valve core
The low side valve contains a JRA valve core

These are different size cores. The valve core "kit" was less than $9 from Amazon - Four Seasons 26783 Cap & Valve Air Conditioning System Seal Kit. It has two of each core and new caps to replace the old ones.
The tool you need to replace both Standard and JRA is the Mastercool (58531) Black R134A Standard and JRA Valve Core Remover. There might be others. This was $75 from Amazon.

I've attached a picture of the whole shebang, including the old valve core that I removed. There are videos on YouTube showing how to use it. I'll say I scared the crap out of myself by not completing enough turns on the first try and pulling out an empty tool (no valve core), but I went back in and there it was. Added a bit more refrigerant, and she's blowing cold and the detector shows no leak. I know adding refrigerant to the low this way is probably not the best approach, but it's an old car and I'm not too interested in dumping a lot more money into it. Hope this helps somebody. In the picture, the Leak Detector is the thing with the goose neck. Sensor is in the end of that.

 

THANKS, that's an interesting tool, I wasn't aware of this. But I haven't had the need (yet) because the only time I had a leaky valve it was simply the core was loose and tightening it solved MY leak.

 

Yea. No such luck here. Tried tightening first and no joy. May never need the tool again, all told it was about the same as an "honest" service call ... who knows otherwise.