Help With A/C Recharge

[Newsboy]

My 1990 no longer blows cool air, and I'd like to top up the R-12. I have the R-12,
and a set of Robinair Guages. My understanding is that you warm up the car,keep it at 2000 R.p.m., AC on, temperature to Blue dot, fan on high. Hook up to the low side on the compressor. Does anyone know what pressure indicates that the Freon is low, and what pressure indicates full? There is no site gauge. so other than pressure,how do you know when it's full. I also have a 4oz.(113 gram) can of R-12/oil. Should this be added also? How much?
The total system holds 930 grams. I was thinking, that I would add 1 can (340 grams), and see if it starts to cool.
Any help from someone who's done this would be appreciated.
Thanks
__________________
Steven

[kuehl]

I would not recommend you waste your time or refrigerant without first reading a few books and working with someone whom has the experience, however here are some pointers and they are not complete, just the basics, a dozen policeman and the men in black are going to jump down on this thread:

Always were safety glasses, never work with refrigerant near open flames, wear gloves.

You have a leak so what you put in it is going to leak out, maybe today, maybe in a month. So consider inspections to determine the leak source and plan to fix it.

If the system takes 930 grams you need about 32 ounces of refrigerant plus the oil. Knowing you have ac leaks and you probably lost oil over the years you will want to use all the oil to be safe.

You should pull a vacuum on the system first (assuming there is no refrigerant in it) and do a brief vacuum test to check for gross leaks. If you have no gross leaks you would continue the vacuum procedure and purge the system (another story).

Besides putting in the weighted amount of refrigerant required you need to use a Pressures and Temperatures chart (for R12 in this case) to verify if the system is working properly.

I can understand a need to get the system up and running with this heat wave however doing it correctly is the one way to do the job right once.

If you need the name of a few shops out by you drop a PM and we'll try to assist you.

[peritus]

I recently went to see an AC garage and the owner (who knows 911s and restored a 912), had a special fitting that enabled me to fill up my stock AC with R134.

I cautioned him, reciting all kinds of facts I learned on Pelican when I was researching... changing hoses, some seals, some other hardware.

He told me not to worry about it... Connected his gauges and went to work...

15 minutes later, while driving away, I was so cold that I had to turn it on low!!!

So far, so good!

[911jettat]

Like James' experience, a local German car repair shop just converted my R12 system to R132b with no problems. They sucked the R12 out, PLUS they removed any moisture from the system...saw that the AC system was holding pressure, added new fittings and I was racing down the road with ice cudes coming out of my dash vents... The whole process took 1 1/2 hrs.

[peritus]

Originally Posted by 911jettat

Like James' experience, a local German car repair shop just converted my R12 system to R132b with no problems. They sucked the R12 out, PLUS they removed any moisture from the system...saw that the AC system was holding pressure, added new fittings and I was racing down the road with ice cudes coming out of my dash vents... The whole process took 1 1/2 hrs.

I think your guy might have been more thorough than my guy... we just pumped the new stuff into the old stuff with a special fitting that he fabbed up! Perhaps he measured before and determined that there was not enough to pump out in the first place?

Do you mind if I ask how much it cost to pump the R134 in? Mine was $120 all in (Canadian). I hope my leak isn't too fast!

[911jettat]

Originally Posted by peritus

I think your guy might have been more thorough than my guy... we just pumped the new stuff into the old stuff with a special fitting that he fabbed up! Perhaps he measured before and determined that there was not enough to pump out in the first place?

Do you mind if I ask how much it cost to pump the R134 in? Mine was $120 all in (Canadian). I hope my leak isn't too fast!

I wasn't quite sure what I was getting into at the time...a buddy was helping me out through this shop. I say that because I wasn't sure if I was getting a "special" R12 refill or what?

So I didn't ask a lot of questions but my every so often my friend to would talk to the mechanic and give me the thumbs up... he said...sucking out the old R12, boiling out any condensation, etc... Only an hour and half later, when I was paying the shop did they first mention it was converted! Actually my friend mentioned something earlier during the process, but I thought I had R12 R 134a confused?! I paid under $120!

[peritus]

Originally Posted by 911jettat

I wasn't quite sure what I was getting into at the time...a buddy was helping me out through this shop. I say that because I wasn't sure if I was getting a "special" R12 refill or what?

So I didn't ask a lot of questions but my every so often my friend to would talk to the mechanic and give me the thumbs up... he said...sucking out the old R12, boiling out any condensation, etc... Only an hour and half later, when I was paying the shop did they first mention it was converted! Actually my friend mentioned something earlier during the process, but I thought I had R12 R 134a confused?! I paid under $120!

Well, I do hate paying too much, but I also hate when my wife complains about the AC not working, so it's a bargain!!

I hope that my premium fee means that he'll go easy on my if / when it leaks out!

[Newsboy]

Thanks to those here and on Rennlist, who provided me with information about undercharging my AC.
Basically, I just charged until I got a low side pressure of 30-35 PSI, and a high side pressure of around 140 psi. System was around 1/2 full. Now blowing very cold air.

[kuehl]

Originally Posted by Newsboy

Thanks to those here and on Rennlist, who provided me with information about undercharging my AC.
Basically, I just charged until I got a low side pressure of 30-35 PSI, and a high side pressure of around 140 psi. System was around 1/2 full. Now blowing very cold air.

Good to hear you have some cold air finally. Just remember:
1) There is a leak somewhere and sooner or later you will be down to '0' refrigerant in the system. As the system looses refrigerant it typically looses refrigerant oil along the way. Running with a low oil charge is not good for the compressor. Hopefully you added refrigerant oil when you attempted to recharge the system.
2) Operating with "1/2" a refrigerant charge is not a wise idea. The compressor relies on refrigerant to carry the oil through the system to lubricate the compressor. A low flow of refrigerant means a low flow of refrigerant oil which is not good for the compressor.

[Newsboy]

Thanks for the follow up. Turns out, there was a leak, as the cold didn't last too long. I have a mechanic friend with a "sniffer" who will help me find the leak. I'll be sure to add oil when I recharge.

[kuehl]

Area's common to sniff:
1) Around compressor clutch (worn or blown nose seal)
2) Hoses in the engine compartment (old hoses)
3) Hoses to drier
4) Condenser (debris collect at bottom of condenser's fins)
5) Evaporator - sniff vents and condensation drain tube (they leak sooner or later)