R12 to R134a A/C Conversion

[larinso]

I think I did something really stupid, and I hope it's correctable. I bought an R12 to R134a conversion kit from AutoZone to put on a 92' Nissan 240SX. The A/C wasn't cold at all, so I figured it needed to be serviced, but realized that it had the old R12 attachments. So I removed the core valve and of course a little more freon was released, but I didn't use a vaccum pump before I added the conversion stem. So, I added the R134a and now my compressor is cycling on and off. On for a second, and off for 15 to 20 seconds. It will occassionally catch and stay on for about 10 seconds and get ice cold, then start the same thing again. I'm assuming that, because I didn't use a vaccum pump to remove all the old R12, that the mix is causing the compressor to do this. Before I performed this stunt, it was working fine. Is there a fix for something like this? And where is the low pressure switch on this thing? I've looked everywhere...

Thanks

[Chezedik]

Having air in your system will not cause that problem. Your problem is more fundamental than that. R134a is not as efficient and runs at a higher pressure to start working. Because of this it is when the clutch nearly cycles out it gets cold, and either pressure is too high and it is releasing the clutch, or you do not have enough volume and you have a problem with a pressure differential. The fact is the craptastic $30 retrofit kits are a joke, particularly on the S13. Your fixes are the following:1) have the system professionally evacuated, replace the expansion valve and drier along with all o-rings, and back-flush the system, when done install either R-12 or R-134a (I would suggest going back to R-12). 2)Check the pressure (with a proper manifold) on both sides, you will look for pressure to be wildly out of whack, say 40lbs on the high and next to nothing on the low, or vice versa. This will tell you that you need more volume (i.e. more gas). If you decide to do this, add an efficiency agent like Maxi-cool or something. You will likely also want to see if you can find someone in the business or call Nissan and see if you can find a new cycling switch designed for use with R134a. To the best of my knowledge it is not adjustable for Nissans like it is for Ford and Chevy. 3) Refill your system with propane or butane. Although not altogether a good idea, it will work (actually rather well) in place of R12. You would find that a lot of R12 produced worldwide has either gas in it, but I think you can imagine why there might be a downside to this. 4) Remove your A/C, save your money, and use the old reliable 2-90 refridgerant (2 windows, 90 mph)

Sorry that the answer is not as simple as you might like, but those kits are dangerous to use, and I think they should not even sell them. I could go on forever about them, because I am liscensed and know what you have to do to do a proper retrofit. The fact also stands that I used one on my last S13, the results were less than satisfying. The condensors are not good enough, I could not find the cycling switch, etc. My last suggestion would be to find a cycling switch from an S14 or some other Nissan made after 1995.

[Dattebayo]

Couldn't you just change over to a 1993 compressor and sweat a new drier in? As long as you didnt lose any of the oil from the 93 compressor and blew the lines, compressor & condenser coil out with some Nitrogen you should be fine.

Im not saying that its the easiest fix, but getting a friends torch, manifold and a stick of sil-floss should save you a bunch of money!

This would best be done on a less humid day also...

[Chezedik]

93 would still be R12.

[Dattebayo]

I own a 1993. Its not R12. You need proof?

You are wrong, sorry!

[Chezedik]

Well then, why did you (illegally) evacuate your refrigerant. I made a mistake, but most manufacturers did not switch to R134a until 1995, so you want to ask for help then try and flame the people who try to help you, then go F yourself.

[larinso]

whoa hold up.... I'm the one who asked for help, and I appreciate the assistance... I don't know where the mix up is but I appreciate both of you guys info...

Thanks

[Dattebayo]

whoa whoa whoa!

Easy there. I was just pointing out you were wrong! Its not personal, just factual. I did not evacuate any coolant or anything. Its stock, the way I bought it.

I hope you have luck with the swap over. You may want to borrow a torch from a friend though

Also, I will be selling mine here in a few weeks. Shout if you need it!