Do I need to change AC compressor for R-134A?

[TrentW]

I have been repairing and recharging automotive A/C systems for years (admittedly primarily non-BMW) and have run into exactly ZERO faulty TXV's. Not to say it doesn't happen, but it usually isn't the cause of a system performance issue.

What does happen beginning with the use of synthetic lubricants associated with refrigerants like 134a and 404a is that high discharge temps. in the compressor tend to "cook" the oil turning it into a waxy substance that plugs up TXV inlet screens, resulting in the changing of the valve.

I was referring to the fact that if your original R12 expansion valve is faulty--mine was stuck closed and wouldn't allow a charge--you're basically forced to use R134a, as the new expansion valves won't work correctly with R12. I had planned on using R12 until this was diagnosed and also found that the compressor was leaking.

[redsubdivisions]

Do yourself a favor and do it right the first time. Cars are an investment and depending on where and what you invest, it will show in the end. I thought I could halfass my A/C system, but I was pretty much mistaken. I ended up revamping the entire A/C system in my car and I have all my hard work to show for it. Warmsquash1 is pretty much spot on.

When I did my system, I replaced nearly everything. Yes, it was a lot of time and money spent, but it was excellent trial and error that I can share with everyone on the forums.

I can't stress enough importance on flushing your lines out as well as doing it right the first time. It's either do it right the first time or do it again and pay twice as much. I replaced the following:

-Compressor: my old one took a shit (I tried to just fill it and let it run R-134 through an R-12 compressor. Didn't work out in my favor). I found it more cost effective to get a reman unit that was readily R-134 compliant. I was getting high readings on my low pressure side and low readings on my high pressure side. That was a dead giveaway that the internal seals were shot.

-Expansion valve: no matter what anyone tells you, R-12 expansion valves will not work with R-134 ones and vice versa. They are two different types of gases with different densities and pressures, so replacing this was necessary in my case.

-Drier: always replace it when you leave the system open for a good amount of time. It's relatively inexpensive and you don't want moisture in your system. It will mess some shit up. also, get the pressure switch replaced.

-o-rings: Basically the same thing with the expansion valve. R-12 o-rings are black, R-134 o-rings are green. Anywhere I opened up a fitting and there was an o-ring there, I replaced it with a new one (which was basically everywhere on mine).

-Condenser (optional): this was the last thing I did and in my experience, it made the biggest improvment in my system. The stock tube and fin design didn't seem that great of a design for R-134, so I got myself a parallel flow condenser (which is what is used on modern cars today) and I am happy to say that my car is able to get into the 30's with the recirculation button on. Infact, I did a write up on it (under the FAQ section: Upgrading to Parallel Flow Condenser), so give that a look see if you're interested in going that route.

-Flushing: I flushed all my lines to get rid of any R-12 gunk or residue that was left over. I also pulled out my evaporator and washed that down (don't flush the inside of it; I washed the fins out. They were dirty). this is especially important to do considering if there are any foreign partices or other junk in there and you don't clean it out, it will cycle through your system and put your compressor in a world of hurt.

that's pretty much it. Like I said, this was in my own personal experience and I replaced all this for solid piece of mind. I know it's pretty much overkill and I almost feel like I just went into a ramble, but hopefully someone finds this useful. lol

[TrentW]

I heartily agree and did the same with mine--except that I kept the stock condensor, just flushed it out. We'll see how it turns out in a few days when I take it to my a/c guy.

So why not flush the evaporator? Like I did last week...

[redsubdivisions]

You can flush it if you want, I just read up that and was told not to do so.

[Ryann]

what kind of temperatures can be expected using this?

You can expect 45-50 degree vent temperatures in a clean and healthy 414b system.

redsubdivisions- I completely concur so far as a converted system is concerned. If you're going 134a and want it to work/last then do it right. R414b is however THE PERFECT solution for people who developed a leak, fixed that leak, and need something to put back in that will work properly without worrying about oil compatibility and pressure issues that come with 134a.