A/C gas preassure ???

[hyperkinesis]

Hi my 1981 911 A/C was mod with a R134 Conversion Kit
in addition the evaporator was change for a Rennaire evaporator and a pro cooler kit to replace the receiver/drier. I want to know how much gas I have to add to this system and the temp expected for this system???

[mtb001]

mine took approx. 28 oz once converted.

[kuehl]

What do the instructions say?

[brads911sc]

The amount of refrigerant is immaterial.

You want to measure hi and lo pressure at 2k rpms and system on full blast and be within the pressure range for the ambient you are in.

Originally Posted by hyperkinesis

Hi my 1981 911 A/C was mod with a R134 Conversion Kit
in addition the evaporator was change for a Rennaire evaporator and a pro cooler kit to replace the receiver/drier. I want to know how much gas I have to add to this system and the temp expected for this system???

[brads911sc]

Come on Griff. you know Your kit is the only one that comes with REAL instructions.

Originally Posted by kuehl

What do the instructions say?

[Mitch Leland]

When I installed my Pro-Cooler I never understood the directions and hose layout. This is someone's picture and member russnak did the graphics. Maybe this will help you...

[Flat Six]

Originally Posted by brads911sc

The amount of refrigerant is immaterial.

You want to measure hi and lo pressure at 2k rpms and system on full blast and be within the pressure range for the ambient you are in.

+1

And rear decklid nearly closed . . .

[88911coupe]

What has confused the heck out of me is that I don't see the expected vent temps based on the pressures I'm showing on the gauges. Even with a pro cooler and additional condenser with a fan.

[db_cooper]

Share the high/low pressures and temp your getting and at what ambient temp/RPM?

[hyperkinesis]

Local ambient temp is around 95 to 98F on sumer and 80to 90 the rest of the year.
Im goont to verify the A/C at 2k rpms and system on full blast. BUt the preassure range I want to be sure of that any recomendation?

[brads911sc]

A good High Temperature Reading for 134a = twice the ambient temperature + 50.
For Example at 85° F, you would expect a high side pressure of 85x2=170+50 = 220 psig.

A good Low Temperature reading should be between 30-40 psig.
This means the temperature of the refrigerant entering the evaporator is between 35 and 40° F

Originally Posted by hyperkinesis

Local ambient temp is around 95 to 98F on sumer and 80to 90 the rest of the year.
Im goont to verify the A/C at 2k rpms and system on full blast. BUt the preassure range I want to be sure of that any recomendation?

[hyperkinesis]

thanks for the help....this is a GREAT forum

[88911coupe]

My problem is I'm seeing the pressures about right with the low side in the range of 30 (ambient 90's) and the high side being 250 or a little higher. However, the vent temps barely get below 50. I've played around with the pressures and let the "freon" out to lower them but no improvement in vent temps. Currently I'm using ES12 but would be quite willing to just go to R134 if that really is better.

[hyperkinesis]

In Puerto Rico climate a A/C tech told me that in high rev the preassure cant be more than 200psig and lower 30-40psig using r134a. If is set more than 200 the seals probably broke

[88911coupe]

Interesting, I've seen several references here on Pelican to high side pressure being over 200 but not with any warnings...

[bazar01]

Originally Posted by 88911coupe

Interesting, I've seen several references here on Pelican to high side pressure being over 200 but not with any warnings...

+1

It's typical to see >200 up to 250 psi, but <300 psi in 98F-100F outside temps.

[brads911sc]

Ive never heard that...

Originally Posted by hyperkinesis

In Puerto Rico climate a A/C tech told me that in high rev the preassure cant be more than 200psig and lower 30-40psig using r134a. If is set more than 200 the seals probably broke

[kuehl]

Originally Posted by hyperkinesis

In Puerto Rico climate a A/C tech told me that in high rev the preassure cant be more than 200psig and lower 30-40psig using r134a. If is set more than 200 the seals probably broke

Ask the climate AC tech what P&T means

[kuehl]

Originally Posted by 88911coupe

My problem is I'm seeing the pressures about right with the low side in the range of 30 (ambient 90's) and the high side being 250 or a little higher. However, the vent temps barely get below 50. I've played around with the pressures and let the "freon" out to lower them but no improvement in vent temps. Currently I'm using ES12 but would be quite willing to just go to R134 if that really is better.

A better measurement is at idle.

On a sunny day;
You can have a 90F ambient on the lawn next to the driveway.
Measure the ambient around the car that is on black top adjacent
to the lawn and it can be much higher.

Assuming you are at 90F with R12, at idle you'd want something near 216 psi.
With R134a 238 psi would a be perfect world.
If you have 250 then there is another issue going on, such as:
air in the system, overcharge, front condenser fan no working,
deck lid was up.

[Bob Kontak]

Originally Posted by 88911coupe

However, the vent temps barely get below 50.

I have not seen sub 50F on the stock/near stock systems I have worked on and that is with R12.

50 is pretty chilly. To get 35 you need to spend about a squillion dollars.