svs

iTrader: (1)

My A/C system is ready to evacuate and charge. I have access to the equipment to evacuate the system. I simply don’t have any R12 to charge the system with. No one will sell the little bit of R12 they hav left for anything other than topping off a system that is already full of it. (Mine is empty.) The eBay cans look iffy, aren’t returnable if bad/empty, and will take a while for delivery. I'm also hesitant to scan a Freon license and email it. (Plus, I have no idea what the previous owner may have done to the A/C system.)

Since the dryer has already been replaced, every A/C tech I’ve talked to recommends converting to 134a. They all seem to think it is as simple as adding fresh oil, evacuating, and filling with 134a. If it really is that simple, I should be able to convert the system myself. The consensus is clearly that I shouldn’t convert to 134a if I don’t have to, but I don’t really see another option.

If converted, my plan is to:

1) Evacuate,
2) New fittings,
3) Add 6oz of propellant driven Ester oil,
4) Add 25oz +/- of 134a.

Am I missing anything? Which oil is the easiest to remove if I want to go back to R12? Should I just take this whichever A/C tech looks the most upstanding?

This seems to be harder than it needs to be.

scrip7

iTrader: (6)

Converting to r134a with the list that you gave should work and cool, but keep in mind with the original equipment condenser your dash vent temp will not likely be as cold as r12 and will take longer to get cold. I have been a tech for 30 years and have been converting to r134a since 1994 and the secret to getting r134a to cool like r12 is entirely related to the efficiency and capacity of the condenser and the amount of airflow going across it. The original condenser in rx7s is what is called a "serpentine flow" condenser. Gases from the compressor enter the tubing at the top and work its way back and forth towards the bottom and then onto the expansion valve. This type of condenser works fine with r12 but with such a crappy refrigerant as r134a, it's best to use what most newer cars use which is a "parallel flow" condenser, built with an aluminum core that functions much like a radiator and has considerably more efficiency. You can do a google search for this type condenser, they are available for around 60 to 100 bucks. If you plan on using your old condenser, make sure you don't make the mistake that lots of rx7 owners do by converting to an electric fan. Most of these don't have an adequate shroud and most don't cover more than about 2/3 of the surface area of the radiator. Try to stick with the stock fan with a good clutch or use a Turbo II fan which has 10 blades instead of 8. Hope this helps.

svs

iTrader: (1)

Thanks. You're reply was very helpful.

Steel

Or use freeze-12. Its a close substitute to R-12, except legal. Search the forum for more info.

bigzman

iTrader: (1)

I put freeze 12 in my car and it blows cold, Now all I have to do is find that damn slow leak.

arghx

iTrader: (3)

I have a ghetto r134a conversion. The problem with running r134a in an r12 system is that it will be pretty inefficient when it's really hot out. When you need it the most it will not blow very cold.

jackhild59

iTrader: (7)

This is pretty accurate.

If you are not going to replace the condensor with a parallel flow, then either use Freeze12 or go back with r12.

Now, it sounds like you are going to give 134a a try anyway, hence the oil question. Please use Ester oil only if you are ever going to go back to the R12. PAG is totally incompatible with Chlorine which is part of R12 molecule. The pag will react with the R12 and you will be in for an expensive and extensive flush job. Probably would lose your compressor and clog your condensor and expansion valve to boot.

Again, ester only.

Good luck.

svs

iTrader: (1)

Thanks. Great advice.

Everyone's replies have really helped me clarify what I need to do.

arghx

iTrader: (3)

A large portion of freeze 12 is R134a.

Sideways7

iTrader: (7)

That doesn't change the fact that it works better than R134a. I have it in my MX-3 and it gets down to 38 degrees very rapidly. You can get conversion kits to properly and legal convert it to freeze-12 online. You still have to have the liscense to legally buy Freeze-12, but all it takes is a really easy open book test here: www.epatests.com. Its the section 609 test.