Got an A/C question please help!

[scot w.]

I have a few A/C questions about our cars. I do a/c for a living but residential and industrial. was wanting to know how much 134a charge to weigh in? Mine HAS been converted to 134a. The correct charge for the R-12 is (3.24lbs). I know that you should weigh in 85% of the R-12 charge for 134a wich is (2.76lbs). Can anyone tell me what they weighed in there car to get it the coldest?

*Most Important* When looking at the LOW SIDE gauge. do you go by IDLE or around 2000rpms for reading the correct presures? So far today at idle I would have too much in it, but at 2000rpms it's at 32 on the low side gauge

PS:
1). PLEASE reply with the correct weigh in charge for 134a, or what has worked best for you.
2). PLEASE reply with the correct way to read the low side gauge, AT IDLE or AT 2000rpms..

Thank you! Scot w.

 

[SPS]

I never really had luck weighing in with a conversion. Starting at 85% is a good baseline. Every car is going to be different. The best method I have used (cant use superheat and subcooling on cars-no specs from the factory) is to start by placing your temp probe in the vents. After weighing in your start up charge let it run for at 10 minutes. You are looking for the coldest air possible. Want to be at least 60 deg or below. On your gauges you want to check at idle, low side should be around 40psi and high side should be around 200 psi. Adjust charge to achieve the lowest air temp and check gauges. If pressures are way off, start diagnosing as you would comm/residential- check airflow across coils, make sure the oriface tube was clean, also make sure there is not a build up af leaves in the evap coil box. make sure the recirculate is on and the doors are stuck sucking outside air. You did replace the dryer right? And clean out the old oil? feel free to email me with any questions

 

[scot w.]

A/c

(SPS) The conversion was already done when I bought it. I know the charge on 134a is kinda critical. Well i'll try what you mentioned and see how it works. Thanks, Scot w.