LT1driver

converted from r12 to r134a, what is the high pressure supposed to be on average?? thanks.

PhotoVette1

Depends on type of system, engine speed, and condenser inlet temperature.

DonBecker

why do you need the high pressure?

is anything not working correctly?

Robby79

The Low and High pressure readings represent the systems freon charge and also the calculated or theoretical skin temperatures of the evaporartor (Low) and condenser (high).

For a quick check, set the fan speed (inside) at high and system set to recirculate the air, all of the vents open, the car shaded ( I see your in West Texas so do this with the car out of the direct sun) and most importantly with air moving across the radiator and condensor (setup a box fan in front of the car).

With the car at normal operating temperature and your AC system properly charged, the low side will read about 30-35# (35-40 drg. F) and the high side no more than 150# (112 drg. F). There are a number of other varibles that will impact the reading including the ambient temperature and humidity, mechanical condition of the compressor, expansion tube and the total amount of oil so these are only guidelines.

Keep us posted and good luck.
Robby

PortDawg

I read someplace you should only fill 134a TO 80 percent of the capacity of the R12. Don't know if that's true but....

zwede

Robby: 150 lbs hi side sounds like the R12 spec and assuming a cool day of around 70F or so. With R134a and the 90f we're having here in TX right now you'll see much higher than that. On my 71 I would expect 240-280 on a day like this.

zwede

I actually had the best result when going even lower. I do 70%.

Robby79

Zwede,

No argument from me. I almost didn't reply becasue there are so many varibles that need to be considered. Do we know yet what the measured pressure was?

Robby

mrvette

I usually put in two 12 oz cans and call it a day.....suction reading around 34 like stated above, I don't even have a high side fitting...

GENE

zwede

Yeah, it is hard to tell what the high side "should be". Many many factors including the phase of the moon it seems. I noticed factory R134a systems will run around 150-200 and converted systems 200-300.

LT1driver

thanks guys, high was 260-275 range with low at 20, put in 2 cans of 12oz each. outside temp around 94, in shade under carport.

zwede

You're good!

rafto

Here's the place to go for info: http://www.autoacforum.com/categories.cfm?catid=2


Here is link for a/c evacuation and charging instructions

http://www.autoacforum.com/messagevi...&threadid=7931