viktorch

Hi, I am trying to get the ac on my GS430 to work. The pressure between the low and high sides equalize. But when the compressor is running, the low side pressure only drops 10 to 20 psi. The high side pressure barely increases. So, thinking it was the compressor, I evacuated the system and took the compressor out. Found out it was an internally variable displacement compressor. Took apart the compressor. Everything was in amazing condition. Tested the mechanical control valve using an air compressor. worked perfectly. Replaced the o-rings. Was a little low on oil. So, i added 2.5 ounces of the correct pag oil to the compressor after lubing all the various parts and put it all back together. Installed the compressor back on the car, evacuated the system for an hour and made sure the pressure was held for a day. Charged it with one 12 ounce can of refrigerant. Compressor is running but I see the same behavior as before. Any feedback much appreciated? Is there a specific high pressure that has to be reached, before the displacement of the pistons increases. Seems like I just cannot reach the max displacement of the compressor pistons. Seems to be stuck at the minimum displacement. Help!

TrueGS300

Dude, just replace the compressor, the thing's worn out. It's gonna look clean inside. It's not exposed to any elements. If it turns on, and you see the pressure change, but just barely, then there are just worn out components inside. I picked up a $40 remaned compressor on flea-bay and it has blown Ice cold for years now. There's cheap options for these car lol.

viktorch

To anyone dealing with lexus GS ac compressor issues similar to what i had posted in my original post above, i have resolution. The problem was only with the variable displacement mechanical control valve. The ac compressor is almost 17 years old (~130k miles); but it was in immaculate condition when i took it apart. Low on oil. So, as i mentioned above, just add a couple ounces of the correct oil as recommended by the manufacturer. Just bought the mechanical control valve from ebay for 20 bucks. Replaced it, mounted the compressor, vacuumed, and charged with a couple of cans of R134a, and it worked like a charm. So, if you see the same behavior where the high side pressure won't go up, it is because the R134a is leaking from the high side due to an aging mechanical valve spring. If you do not want to spend the 20 bucks, you can take out the mechanical control valve. There is a plastic filter near the top of the mechanical valve. Cut it out. There are four small equidistant holes under the filter. Just seal them so that the R134a does not leak from the high side. Replace the small rubber o-rings if need be. The original o-rings are of very high quality and should still work in case you do not have replacements. Put the mechanical valve back in. Install the ac compressor and vacuum and charge with R134a. Because you sealed the high side inlet holes, the ac will no longer work as a variable displacement ac compressor. But rather it will work like a normal ac on older cars, where the electromagnetic coil will engage and disengage the ac compressor as needed. The ac performance will go up as a result. But, it has other shortcomings. Great article explaining this can be found at :https://axleaddict.com/auto-repair/V...nt-Compressors My 2003 GS430 ac compressor was in great shape and I think it will last another decade or two(knock on wood). So, don't go buying a new ac compressor or a cheap alternate, unless you know there is something broken. There are tons of videos on youtube which show you how to fix these compressors without too much effort. Unless of course it is burnt or broken beyond repair. Also, this post is only for mechanically controlled displacement valves. NOT for electronically controlled displacement valves. Disclaimer: Fix at your own risk Good Luck!

TrueGS300

Good work fixing your compressor. I do respect the effort. Just seems like a little too much time and effort. Especially to have the car down all this time if someone didn't have more than one vehicle. $247 for a new Denso unit on Rockauto is probably well worth it to not mess around with it. But like I said, I do think it's cool you figured it out. It's just not something anyone is going to do..

viktorch

To be honest, it wasn't much effort at all. It is my second car. I would say two weekend's worth all together for ac work, even if that. I am mechanically inclined and it is all about figuring it out. The car needed major overhaul. So, most of the time was spent on water pump/timing belt. Radiator had a leak with transmission fluid and coolant mixing. Radiator had to be replaced. Along with engine flush/ transmission flush. That is what took up most of the time. I work on it when i get some time. A lot of people just get rid of the compressor even when the only thing wrong is the mechanical valve. So, I do not see why people would not take advantage of this information. If you have access to the mechanical valve under the car, you do not even have to remove the compressor after evacuating! It only takes two to three days to get the part from ebay. I do not see why people would not take advantage of that. There is a lot of sense in replacing things with a new part-- no question about it. Just giving options to people who are mechanically inclined.