RayfenWindspear

Stock AC compressor blew and I was quoted $1200 to replace the full AC kit. Decided to pay $300 for all new parts and do it myself, boy was that a chore. Was a fun learning experience though.

Fast forward to now. Everything is together and charged, no leaks (oil came with UV dye)... buuuut, the air coming out is totally wussy and it's more comfortable to go windows down in 95 degree weather. I have a few suspicions, but wanted to confirm things before I go evac and start wrenching things.

First thing of note is that low side is like 30 PSI when it's 95-100 degrees ambient, while the high side seems to be mostly normal. I wanted to verify my research on this before chucking things. From everything I've read, this indicates a faulty expansion valve, doesn't it? I can get a new one for like $15, and I made sure to only put the bare minimum of the evap/blower assembly together in case something didn't work out, but I'd rather be sure before I make any moves.

The other thing that may be an issue, and not my brightest moment ever... but I originally couldn't figure out how the R134a can piercing attachment thing worked, so as much air as would be in the yellow line and whatever else would be in the closed off manifold gauges would have entered the system. Basically I knew I was supposed to press the purge valve (and did), but I hadn't unscrewed the puncture pin from the can, so obviously nothing came out. Would this be enough air in the system to be causing this issue? It was on vacuum for something like 4 hours prior, so that's all there would be, just what would be in the yellow charge/evac hose.

Any assistance would be helpful.

Thanks

99stockcivic

Have you tried one of the gauges that shows if the air conditioner freon/R134a is in the high, medium or low range? You could have air, in which case I don't know how to fix that except release a bunch and recharge it, getting some of the air out, or if could be overcharged, and it will run not as cool as when properly pressurized. Did you take pics of the process to put in a a DIY, I bet a lot of people would be interested in how you did it. I've never had to take mine apart, but I have replaced the pressure valves and replaced with a can or two of R134a.

RayfenWindspear

I've got a set of manifold gauges I'm using to test. The issue that keeps tripping me out is that for 95-100 degree ambient temps, the high pressure is pretty much spot on, but the low pressure often sits around 28-35 psi, where it's supposed to be like 50-55 (according to the charts I've seen). I think what I'll try doing today is to add just a tiny amount more refrigerant to the system and see how it reacts. I'll add by weight and if things don't go well, I have empty cans I can pull some back out of the high side... unless, does anyone know if that is just a super awful bad idea, or is that safe to do? I can always loan a vacuum pump if that's the way to go. A slight inconvenience, but better than a can exploding on me.

A DIY guide would be a good thing to do. I watched a number of youtube videos where people removed way more components than I was willing to do, and found ways around such removals that could be useful to others. Specifically, I found access to the filter/dryer and compressor without removing the power steering and cruise control. Just removing the power steering reservoir mount and moving it was enough. Not for big hands though, mine are pretty normal size I guess. I also removed ALL the pipes/ducts so I could flush them vertically and would have advice to give on that, specifically that you don't have to pull the radiator to get them out as most guides recommend.

RayfenWindspear

The more information I absorb on the matter, the more confused I become. I began searching side effects of over/undercharge and, at least according to one article, lower pressures on the low side are actually better... but that was followed by a warning that too high pressures on the low side could cause liquid refrigerant to enter the compressor and destroy it. Now I'm kicking myself for not saving that link so I could reference it here.

I still feel it a decent assumption that, given the compressor has a minimum low pressure threshold which will cause it to disengage, the low side should be within the recommended ranges given by recharge charts instead of pretty much hugging that threshold pretty close.

RayfenWindspear

Almost feel like I'm talking to myself here, but this might help others. TLDR; air BAD!

Ran more tests, added a little more, pulled a little out, think I finally settled on what is going on. First off, I guess I'm kind of a wuss in the heat, because according to this chart I'm getting vent temps at the very coldest range of normal (albeit my humidity is 10-15% and the chart stops at 30%). Second, I'm pretty sure I previously had the charge a little off, but tinkering with the levels and seeing how the system reacts was a good experience. And last, BUT CERTAINLY NOT LEAST, discovered just what that little bit of air I didn't purge out does to the whole process. Now I'm still not 100% this is the issue, but everything points to it and I'll be sure to follow up if this is not the case.

Again, I got the system to the proper charge, as it was indeed low, but not by much. This caused idling pressure to be low on the low side (28-32 psi) while high side was mostly within normal ranges. Check. Got everything in normal ranges while engine idling (and yes, letting it warm up makes a difference). Now the real concerning thing was that things weren't holding properly when I'd peg the engine at 1500 RPM. Things were making me mighty worried... like the fact that things would immediately get imbalanced, and even worse, after like 5 mins of holding the throttle, both pressures would just keep climbing... and I mean climbing. I could get the system (at ambient temp 95) to go 450 psi on the high side, and low would match at about a 1:10 ratio. It would start like 30:300, then both would climb to 45:450. Way low on low side and crazy high on high side. Then when I'd let the throttle off, it would immediately drop like 50 psi on the high, and raise to like 70 psi on the low, which would kick the compressor off, but not before almost killing the car. Sure enough, I check the sheet I linked above (which is a complete favorite resource now), and, you guessed it: "air in system".

I'll be doing an evac and recharge with a proper yellow line purge this time. I feel a little silly all of this was caused by not knowing how the little puncture pin attachment things work for the recharge cans and the manifold gauges. Would have been avoided had I used a simpler recharge head, or just knew I how much I needed to evac the system again after letting that bit of air get in. TIL

RayfenWindspear

Took my civic in to have it recovered and charged for realzies. Blows more ice cold than it ever has. Even small amounts of air in your system can cause some serious problems. Don't let it happen to you!

On a separate note. The guy charging it had a few WTF moments. I came to pick it up and drove away with it pumping out hot air. The compressor clutch was engages and everything. I came back and the guy was like WTF, the system is totally empty!? Pulled a vacuum and charged it again... system freaking out. Something funky happened and maybe the refrigerant was trapped somewhere? I dunno, hopefully nothing weird happens later. After a few pumps back and forth into and from the system, everything is working right. He said to call him if something bizarre happens.