Thanks Guys!

 

First you need to figure out what coolant the system requires.
It will be either R12 or R134.

If it's R134, the procedure is pretty simple.
http://autorepair.about.com/od/regul...C-recharge.htm

 

1st I guess we assume yours is empty? If so you need to find the leak. Next you would need to determine if you want to fill it with R12 or 134 freon. In either case you would need to replace the receiver/dryer and the orifice valve. I would also suggest you flush the system. When you are ready to refill the system you would need an oil charge and then the freon. You can fill it at the rear of the compressor or you can fill the low side at the receiver/dryer. Wear the appropriate safety equipment and follow the instructions on the freon cans.

 

Given the elevated price of R134a these days, I'd really recommend having a pro do it. As has been mentioned, the previously existing refrigerant went somewhere. A shop will evacuate the system, extracting any moisture that has accumulated. They then do a leak test which basically consists of pulling a good healthy 25in. of vacuum and monitoring it for 10-25 minutes and observing if the vac holds or whether there is a gross leak. Your 90 model was R12 originally. Check the accumulator on the passenger firewall to see if the fittings are Shraeder valve (like a tire valve) or are larger and of the push/pull variety. The latter are R134a fittings. After the shop leak checks it and assuming they find no gross leaks, they can just add an oil charge and fill it up w/ R134a. I'm in Texas where a/c is a must, There is no mystery to converting from R12 to R134a. All that is needed is to extract all the R12 (usually has been gone for years anyway) as well as the mineral oil lube used w/ R12. Getting every last drop of mineral oil isn't necessary anymore as the industry developed PAG and ester oils that are compatible with trace amounts of the mineral oil. Flushing a 20 year old system is a toss up. To do it correctly means dismantling the system at pretty much every connector. In my experience, the power flushers that don't involve opening the system are at their best extracting money from the customer's pocket but little else. The 240's and 740's don't have an orifice tube so that doesn't need changing. A new accumulator/dryer is a good thing as it has a desiccant bag in it that helps keep the moisture from the rest of the system but, again, if money is tight, it can be left for now. Be sure that fluorescent dye is added so if the charge leaks down the leak can be identified.

 

Be sure to check your fittings.
I had a very tiny leak that took a week or two to diminish the A/C.
Nothing was obviously leaking.

Until I went to change the oil and bumped a fitting with my shoulder.
The steel hose snapped clean in two spraying coolant all over me.

None of the parts stores in town had the correct line and the only online seller wanted $200.
The plumber in me went "looks like a pipe".
So I found the right size compression union and it works better than the factory fittings.

 

Thank you everyone for all your replies!! I really do appreciate it!

Scott

 

I have a Volvo 1990 760 GLE. I need air conditioning recharge stop leak. How do I figure out if I need R134 or R12? Thank you.

 

The charging ports are different between r12 and r134.

r12 fittings look like a tire valve and are the same size low and high, r134 fitting look like the picture - and high and low side are different sizes

(And I would avoid any product that is a "stop leak" for your ac system!)

 

Thank you so much for this information and letting me know not to use stop leak! I'm curious, why not use stop leak? Thank you again!

 

Stop leak tends to clog your $5000 recovery/recycle/recharge machine that is typically used (in a shop setting) to evacuate and recharge AC systems. And Your stop leak - is not going to fix anywhere those systems commonly leaked - the evaporator. But at this age - could be anywhere!

Your 1990 would have been built as a r12 system. To convert it - the Volvo kit had you change the compressor oil (from mineral to PAG oil), the expansion tube, the accumulator, added fittings to fit r134 and a sticker for the top of the accumulator. The systems worked very well after conversion using r134. The compressor oil is changed to PAG oil because chemically r134 does not mix with mineral oil. The compressor is lubricated with oil mixed with the freon and if it does not mix - the compressor fails shortly after that.
Many aftermarket solutions exist - the most simple being screw on fittings to convert r12 fittings to r134. (and not changing the compressor oil or any other parts)

 

Stop leak formulas include small bits of material that will hopefully get caught in the leak and make a seal. These small bits will also clog stuff that you don't want to be clogged up.

Most cars have a sticker under the hood or in a door jamb to say which refridgerant to use. If the car is older than a 1993, it most likely used R12 - which is now banned, is extremely costly and difficult to source. You would want to have a pro do this and fix the leak first. There is the option of converting to R134 but it will require installing a new compressor and some other components like installing new o-rings for all the lines, new expansion valve, new port fittings etc.

you can google for a R134 conversion kit as well as forum posts for people who've done this to get an idea of the steps.