What cycles the AC compressor?

[JONAS78028]

Where were you able to find the r12? I've been looking on ebay and don't want to get ripped off but I have my Eagle and a 71 ford pickup that haven't been converted yet.

I actually have a stash of R12 
I'm so used to having to replace bad compressors that I am just in the habit of converting systems over to 134a.  This car came to me with a sealed R12 system that was good so I just pulled a vacuum and charged it. 

[JONAS78028]

Well, I got it working... woohoo!
There was very little charge in it so I pulled a vacuum for an hour and let it sit overnight.  I put in 28 ounces of R12 and it's putting out 44 degrees out of the dash vents.    I may try to fine tune it later but I'm pretty happy with that for now. 

[trucker79005]

I actually have a stash of R12 
I'm so used to having to replace bad compressors that I am just in the habit of converting systems over to 134a.  This car came to me with a sealed R12 system that was good so I just pulled a vacuum and charged it.

I haven't read enough yet to figure out how to tell if my system is good without charging it... The mechanic I was planning on using said he really didn't have a way and that pulling the vacuum would only tell him it didn't have a Big leak. Said the only way to know how it would handle hot days and high pressure was too charge it and i don't have a stash

I did look on craigslist and most of it is outrageous but I did find a 30 lb canister that if I could figure out how to get it i think I could get the mechanic to go in on it with me..lot of money up front though.

[AMC1]

I don't know why more fellows don't switch over to R134a. I bought an AC system a few years ago & switched it over before installation. Admitedly  I have a small nasty leak which requires 4-6 ounces per season. I filled it a couple of weeks ago & its very cold in the car. I purchased (5) 12 ounce cans for $4.89 each but could have bought a 100. That should last 10 years If I never get around to fixing that leak.

[trucker79005]

I'm curious what you mean. What components did you buy and what kind of money did you put into switching? I was looking at compressors and driers and they don't seem too cheap.

[mo.eagles]

Those AMC Jeep/Renault  cans might be worth something . Museum quality .

[rollguy]

I'm so used to having to replace bad compressors that I am just in the habit of converting systems over to 134a.  This car came to me with a sealed R12 system that was good so I just pulled a vacuum and charged it.

If the system was empty enough to pull a vacuum, then for sure you have a leak. If the system had a quantity of R12 in it before vacuuming, then pulling a vacuum is akin to releasing refrigerant (venting), and is illegal. It is wise to pressurize the empty system with nitrogen and check for leaks (and fix them) before charging. With the cost of R12 (and the scarcity of it), it is best to ensure there is no leaks. As far as those "designer" refrigerants (Dura-cool, Freeze 12 etc) go, they are not "drop in" as they claim they are. Most are blends, and blends leak at different rates (different size molecules). They also are not compatible with some oils that may be in your system.  It is always best to start from scratch and do it right the first time. Find leaks first, replace leaky components (hoses especially), flush remaining components (drain the oil from the compressor-not flush), check for leaks again, and then charge with the proper amount of oil and refrigerant. Never use vacuum for checking leaks!!!  Always replace the receiver/drier, Orings (oil them), and expansion valve (especially if changing to a different refrigerant).  Doing it right the first time will insure many years of service without any maintenance. Also, changing the condenser to a Parallel Flow type will make the system more efficient with R134a. They are fairly inexpensive, and well worth the effort as a cooling upgrade.

[trucker79005]

If the system was empty enough to pull a vacuum, then for sure you have a leak. If the system had a quantity of R12 in it before vacuuming, then pulling a vacuum is akin to releasing refrigerant (venting), and is illegal. It is wise to pressurize the empty system with nitrogen and check for leaks (and fix them) before charging.

I've been looking for someone to pressure test with nitrogen and not having much luck. Is it common practice?

[JONAS78028]

Those AMC Jeep/Renault  cans might be worth something . Museum quality .

Hmmm...  I didn't think about that.  I actually threw the used cans away... dang.

If the system was empty enough to pull a vacuum, then for sure you have a leak. If the system had a quantity of R12 in it before vacuuming, then pulling a vacuum is akin to releasing refrigerant (venting), and is illegal. It is wise to pressurize the empty system with nitrogen and check for leaks (and fix them) before charging. With the cost of R12 (and the scarcity of it), it is best to ensure there is no leaks. As far as those "designer" refrigerants (Dura-cool, Freeze 12 etc) go, they are not "drop in" as they claim they are. Most are blends, and blends leak at different rates (different size molecules). They also are not compatible with some oils that may be in your system.  It is always best to start from scratch and do it right the first time. Find leaks first, replace leaky components (hoses especially), flush remaining components (drain the oil from the compressor-not flush), check for leaks again, and then charge with the proper amount of oil and refrigerant. Never use vacuum for checking leaks!!!  Always replace the receiver/drier, Orings (oil them), and expansion valve (especially if changing to a different refrigerant).  Doing it right the first time will insure many years of service without any maintenance. Also, changing the condenser to a Parallel Flow type will make the system more efficient with R134a. They are fairly inexpensive, and well worth the effort as a cooling upgrade.

Good advice!

[rollguy]

If the system was empty enough to pull a vacuum, then for sure you have a leak. If the system had a quantity of R12 in it before vacuuming, then pulling a vacuum is akin to releasing refrigerant (venting), and is illegal. It is wise to pressurize the empty system with nitrogen and check for leaks (and fix them) before charging.

I've been looking for someone to pressure test with nitrogen and not having much luck. Is it common practice?

I would think that every A/C shop would have the equipment and would do it for you. Yes it is common industry practice, as well as mandated by the EPA. R12 is not manufactured anymore, and the only available source is NOS or reclaimed.  Once it is all gone, there is no more.  Fixing leaks to preserve what supplies that remain, is wise both environmentally, and economically.

[hatzie]

If the system was empty enough to pull a vacuum, then for sure you have a leak. If the system had a quantity of R12 in it before vacuuming, then pulling a vacuum is akin to releasing refrigerant (venting), and is illegal. It is wise to pressurize the empty system with nitrogen and check for leaks (and fix them) before charging.

I've been looking for someone to pressure test with nitrogen and not having much luck. Is it common practice?

Sorry to bring this back from the dead.  but this may be useful to someone.
It's common to use inert dry gasses to pressure test a system.  Garages tend to use Nitrogen for some reason.
You don't have to use Nitrogen to test for leaks.  Just don't use refrigerant.
Any known-dry non-reactive gas that shouldn't be called a refrigerant by the EPA will do the job.
I use Argon from my TIG setup.  It's readily available, to me, since I happen to have two 125cf Argon bottles for the TIG and two Argon CO2 blend bottles along with one straight CO2 bottle for MIG welding. 
If you do party balloons or weld with exotic gasses...  Helium from a bottle will work too. 

Shop air ain't dry so you can't use that.
Propane is also known to the EPA as R290 refrigerant. so you can't use that even though it's not ozone depleting.

[mudkicker715]

No problems with bringing back an old thread. Also if you can pull vacuum on a system over night that helps to get rid of any moisture.