How much freon to put into converted r134 system
 

I'm tired of trying to guess & measure the correct pressures & rpms to determine the right amount of Freon to put into my AC after I evacuated everything. It has an aftermarket evaporator and back condenser and new hoses, but everything else is same as the typical 911/930 AC. How many ounces of R134a would one expect to put back into a fully evacuated system?

Buy the r134a filler/adapter with the pressure guage and follow the instructions.

As I stated in my post, I have already looked into filling by pressure and there are too many variables and uncertainties that way. I'm looking for a quantity (weight) of Freon. I can then reconfirm with pressure readings. I've got plenty of low/high side pressure advice.

Do a research on charging by superheat.

Absent knowing the overall volume of the system there is no way to tell other than an approximation based on the OEM volume and a best guess for change due to the aftermarket components.

This can be a little simpler.

An 89 930 takes 36oz of R12 if I remember correctly. My 81SC takes I believe 32oz but I can't find it in my owner's manual to save my life.

If the 81 930 takes about what my SC does then I would put two and 1/2 12oz cans of R134. That's 30 oz if you do not waste a single drop, but you will. So let's say you get 28 oz in there and then test.

Maybe your aftermarket parts are a little bigger and your high side reads low. Add the last half can. If pressures are too high, bleed some off. You are not really allowed to "bleed some off" EVER anymore, so air lift the EPA/ASE certified wrench in with his equipment to siphon off those two ounces.

I know you put PAG oil in the components, right? If you did not you will have to buy the PAG and enter it into the system.

FWIW - before I knew anything about AC I put twice as much refrigerant into a Honda mini van than called for. Hell, I thought every car took about three cans. It froze the evaporators (front and rear) No explosions, no nuttin', But especially, no cool air.

In short, you ain't gonna blow anything up.

Use the formula twice ambient (at F) plus 50 for high side pressure. Alternatively use the over the counter el-cheap-o gauge.

Have you ever tried to put liquid refrigerant into the low side of the compressor?

If you buy one of those FLAP A/C charging kits, don't expect optimum efficiency from the already borderline A/C system. Instead, take it to an A/C shop so they can do it for you.

There are also online tutorials on how to do it correctly if you're so inclined.

Sherwood

Yes. Every time I add refrigerant. If you mean high side. Nope. Also, I don't actually put liquid in, I let it gas into the system off from the top.

Regarding the OP's desires, he is adamant that he is tired of science. I am giving him a lazy man's way of doing it. It can work. Three or five extra ounces will not explode his system.

I once overfilled my 98 Jeep Cherokee and it spewed out the relief valve in the back of the compressor. Pretty spectacular.

I'm guessing the sticker in the engine bay is gone, right? If still there it marked by the amount of r12 you need that should get you close? No?

My '84 with new hoses and enhanced front condenser and evaporator took 39 oz. of R134a.

Thanks, this is the kind of info I need. I currently have about 36 ounces in mine, its blowing cold but low pressure seems lower than the recommended, but not sure if that should be at 800, 1000, or 2000 RPM, or the guage is not reading accurately or ...... Hence, the need for a weight measurement. I would imagine if you haven't added extra condensers, there shouldn't be much difference in total volume from the stock design to something with slightly modified condensors or evaporators.

Big faux pas. Thanks for the correction Bob. I guess you can tell how long its been since I've mixed it up with R-12/R134a. :)

Sherwood

I'm not tired of science. I know what method is more accurate and what the pros use. They go by weight recommended by the manufacturer. There is no ambiguity with that, no dependence on outside temps, engine rpms, etc. If you haven't added any additional components to the system, the total volume should be pretty close to original, as should be the weight required.

The pros....fill to 80-90% of known capacity and then use pressure gauges to fine tune.

Old receipts for my 81 converted to r134a show 36 oz. after evac. With stock condensers.

In the years I top it off it usually takes 2 full cans and is good. I always buy three but two cans usually gets it close enough in the full range without overfilling.

Some years I do it, some years I have the shop do it. Usually depends on budget, time and how much I intend to use car with ac that year.

Then what are you?

If you know it all then do it and don't suck our time.

Jesus H Christ, what do you need to make everything ok? How can we deliver your requirements to your lap more comfortably?

Out!

Knowing the approximate weight of refrigerant you should have is important, however in the end of your procedure your system pressure should match the Pressure & Temperatures for the particular refrigerant you have selected. Using the P&T method not only insures everything is OK, it also helps you diagnose many problems.