What should the charging pressures be on a 134 auto ac system?Thanks

It really depends on the car usually if its newer car 94up you can look under the hood and there will be a sticker saying this vehicle uses 134 freon and it will tell you the amount of pressure the system holds but for me a rule of ac system charging is use a 2 oz oil charge and 2 cans of freon with the system completly drained the compressor should be kicking in with that amount of freon in it. Next run the ac system which it should be blowing cold but not really that cold and then go for the killer can the 3rd can of freon which will run your as out your car cold with most all mid size to full size car hold only 3 cans of freon exact amounts of pressure does not matter only is it blowing cold because the car will let you know if you have it right to little the hi/lo compressor cut off switch will not cut on the compressor and to much it will not cut on the compressor and your ac system will blow hot air.

ask these guys http://www.autoacforum.com/categories.cfm?catid=2

Great forum,thanks JJ.

Are you converting an older car or is this a late model car that came from the factory with 134?

Just helping out a friend with his Chevy pickup not a conversion.Factory 134