Converting from R-12 to 134a capacity questions.
 

Yellow R-12 Refrigerant Capacity sticker says 47.2 oz.

1) Is this refrigerant only or is the oil included? I don't recall ever seeing this mentioned in the "few" A/C threads I've read.

2) At an estimated 80% - 85% of R-12 capacity for 134a, I'm looking at or over 3 full 12 oz cans.......Seems like too much. I'll be starting with 50%-60% initial charge using small cans and following the P&T charts to optimize the charge.

3) Should I plan on adding 2 full cans (= to 50% of R-12 capacity) to the vacuumed system before starting the car and running the A/C? Will it even take that much before starting up the car and running the A/C?

I got alot of questions - Thanks!!!

1) That's the refrigerant capacity.

2) Sounds like a plan.

3) Starting with a full vacuum and before starting the car and A/C, add as much refrigerant as the system will take. If it takes more than one, so much the better. That said, don't expect it to take even one full can unless you are using a machine that forces liquid refrigerant into the system under pressure.

I'd say you would want to consider filling up the system by reading the pressure rather than relying on capacity. You have done quite a few mods to your system and the capacity will be quite a bit altered from stock or anything resembling stock.

I fill mine too full anyway, so I'll let others chime in on correct high side pressure.

When I converted my '88, I only needed 27/28 oz. of 134. I had to use the cans so I set them on a kitchen scale. With 134, it is best to go by an acurate thermometer at the vent. Add till the temp stops going down. Search on here and you'll get tons of info. Jim Sims has posted some step-by-step info I believe. Ken

950 grams of R134 = 30.5 ounce is the charge for standard 3.2L system
Paul

How much and what type of oil are you using?

6 oz. Ester

I don't remember where I got this from but its what I used when I filled my system for the first time after the upgrades:

Check with a thermometer at the dash air louver closest to the evaporator - add more refrigerant until the cool air temperature stops falling, then stop.

Engine deck lid down and engine running at 2000 rpm to pull air through deck lid condenser:

For 134a, approximate values:

Low side:
16 to 29 psi for 33 to 50 deg F evap temp
19 to 39 psi for 33 to 60 deg F evap temp
25 to 43 psi for 40 to 65 deg F evap temp
37 to 51 psi for 48 to 65 deg F evap temp

High Side:
115 to 200 psi for 70 to 80 deg F ambient temp*
140 to 235 psi for 80 to 90 deg F ambient temp*
165 to 270 psi for 90 to 100 deg F ambient temp*
210 to 310 psi for 100 to 110 deg F ambient temp*

*temperature of air moving over condenser usually measured two inches in "front" (front is side receiving air first) of condenser.
If the pressures you measure are too high and you have air moving over the condenser(s) while you are measuring pressures then you will likely benefit from less refrigerant.

Forget about system capacity stickers and guesses.

Cold vent temp w R134a is all about low side pressure.

Like the table provided above....

"For 134a, approximate values:
Low side:
16 to 29 psi for 33 to 50 deg F evap temp"

Add slowly up to 18-20psi low side. No more. Now stop and check temperature. You should be 33F +_ at the vents.

If not you got other problems.

Higher low side pressure like R-12 levels and you get bad performance no matter how many fancy condensers and fans you install.

It should be 90F ambient or higher or I'd wait to evac and charge also.

High side pressure control is all about fans and condensing.

I'd be a little cautious of the method called "add until its stops getting colder" as I don't think the vent temps will respond so fast and then you will over fill and get poor vent temps.

Unless you really trickle it in there OK maybe

The gauges don' t lie. Some smart PVT formula some guy figured out. :)

If you hit this target.... 18 psi low and 235 High.... with 90F + ambient

http://forums.pelicanparts.com/uploa...1206719997.jpg

Then you will get this.....

http://forums.pelicanparts.com/uploa...1206720085.jpg

Should really have said "add until it stops getting colder - while monitoring the pressures so that you stay within the proper ranges."