AC pressure

[Nick Triesch]

Hi! Could someone please tell me how much pressure there is in a fully charged 3.2 Carrera AC system? Thank you, Nick

[stcan]

Is it R12 or R134A? It's ambient Temperature dependent also. High side of around 200PSI at 80F for R134A
Make sure you test with the deck lid down at idle.
But you should charge by weight. Factory without the extra condenser is around 40oz.

[GH85Carrera]

That is kinda like asking how much throttle do you need to go up a hill.

It it totally dependent on type of refrigerant, and the outside air temperature, and the RPM of the engine.

The low side and the high side have vastly different pressures, and that is why they are called and and low sides.

Static pressure is once again a different number, and high and low will be the same pressure.

We need more info to be able to advise you.

[Nick Triesch]

Man! Sorry! For 134! Did not think anyone used the old stuff anymore. Anyway, thanks.

[Flat Six]

Try this Nick:

[Rawknees'Turbo]

^^^

Those charts are a loosely basic guide at best and don't take into account the types of components in the system (condensing and evaporative volume, etc.) and going by those numbers alone will not result in max performance (not saying they are worthless, but not definitive by any means).

NickNasty, your system is stock, correct (aka - cools well in cold climates!)? Regardless, what you want to do is achieve the lowest possible vent temps your system is capable of, at the lowest acceptable high and low side system pressures. For example, with my highly modded, ballfreezing system, I run lowside pressures of about 28 and highside of about 220, and have 28 degree vent temps (r134 refrigerant) - this is when ambient is 96+ here in TexASS. In other words, much lower pressures than the above chart indicates.

[Nick Triesch]

Raw!!! Thanks!! But to be fair, on a 77 degree day my AC has cooled the car down to 74. I just do not drive when it is really hot . I have found that most people with a 3.2 I know , the AC does not work. Morning drives are so nice anyway. Took my wife for a ride in the summer once and I told her the little vent on the right was all hers. Was not funny to her.

[Rawknees'Turbo]

Down to 74 on a 77 degree day, you say?! Daayyyuuummmmnnnn, you're all set to start a side gig home-delivering perishable foods for Amazon Pantry!!!

[Nick Triesch]

Yup! I wear gloves.

[T77911S]

use the temperature dial on your gauges for the refrigerant you have.
you want around 35 to 40 degrees in the low side and add about 30 to outside temp for your high side temperature.

make sure you have good air flow over the condensers
put a fan at the front and I put a box fan on the deck lid, with it open.
if you don't your pressures will be higher and you will under charge

[GH85Carrera]

Originally Posted by Nick Triesch

Raw!!! Thanks!! But to be fair, on a 77 degree day my AC has cooled the car down to 74. I just do not drive when it is really hot . I have found that most people with a 3.2 I know , the AC does not work. Morning drives are so nice anyway. Took my wife for a ride in the summer once and I told her the little vent on the right was all hers. Was not funny to her.

I drove my 1985 911 to Key West last summer. I had my brother with me. We both dislike sweating. We laughed about how every-time we stopped and got out of the car, our sunglasses fogged up in the hot humid air of Florida. We stopped for lunch, my 911 sat in full Florida sunshine for an hour, we hopped in and inside of 5 minutes it as wonderful cool inside.

On my journey home I was driving due west right into the afternoon sun, on a 100 degree day going down I-40. The sun was shining on my chest. I had to turn the AC temp up because I was getting uncomfortably cold.

Call Charlie Griffiths. Tell him your goals and he will design a AC system that works. After 11 years of use of his upgrades, my AC system simply works. It was not cheap at all, but neither is my Porsche. It was worth every cent.

[kamaro]

I always had problems with recharging ANY A/C system when using the pressure as a reference. When I charged the newly installed A/C kit in my '77 I invested in a A/C weight scale and charged it by the weight, the A/C blows ice cold and ran reliably ever since.

[Nick Triesch]

“ like blowing warm air over an ice cube” did not just happen!! Yes, I’m sure your AC blows ice cold after $1000s in upgrades. But never from the stock system.

[HaroldMHedge]

Porsche's Technical Bulletin (TSB) 9501, Retrofitting R12 A/C System to Refrigerant R134 indicates the R134a capacity as 1220 grams for the 911 Carrera 1984 -1989.

My mechanic used this amount when I converted my 87 Carrera system to R134a. But due to component changes Griffiths system. This was too much refrigerate and my system was shutting down due to over pressurization. I needed to remove some. Ended up buying all the equipment to fill the system myself using Griffiths recommendations.

Best words from my wife was I'm cold.

[86 911 Targa]

Our stock '86 with R134 is set to on=56f, off=40f
with the temp dial set to the #3 position,
ant the fan speed also set to the #2,
in order to avoid evaporator freeze-up on long trips.

Gerry

[Nick Triesch]

And I bet your car never uses one drop if oil!!!!! And is not smelly!!!!