nickg

low side will be in the 30-40 range hi side will be about 200-220. the lower the low side, the colder it will be. these pressures are on a 80 degree day with the car at operating temp. good enough? some people (me included) use the sight glass, charge till the refrigerant goes clear with no bubbles...it is full at that point (this is the standard way to do ac if the exact charge is unknown)

KuHL 951

I thought the sight glass only worked with R-12? Is that also true on cars that have been converted to R-134a? I always thought that if you try to get the sight glass clear on a converted R-12 system using the sightglass that the car would be 10%-15% overfilled.

glencase

Ding Ding Ding, we have a winner of the gold star thank you nickg.

I'll watch the pressure, center register temp, and the sight glass to see if I can get it where I think it should be.

Thanks again everyone for the info.

nickg

nah...that is the old standard way to do it..if it has bubbles, it doesn't have pressure..remember 134 runs at a higher pressure than r12..(about 15-20% higher on a given volume)so that accounts for the lack of bubbles and the clear stream of refrigerant...think of it as a soda bottle, no pressure, bubbles, pressurized, few bubbles
very important thing to remember is that if it is corching hot...the preeures will be way up..I mean WAY up. don't go over 250 psi as the lines will not like it much(or the evapaorater ) I was taught to charge till it was cold and the pressures would follow that pattern along with sight glass. it has never failed me. If you are just topping up, go to walmart and get the refill stuff with oil...make sure that it has oil as if it leaks you will see it and not blow the comresser up for no oil in the system. Too much oil and the ac will creep up in temp with time and get warm at idle sometimes. if you are carefull, you can see any restricted part of the system by touch and sight. the hard metal lines will be hot on high side( the condenser) and will frost or sweat on the low side of the system if you feel a temp variation on the line or from the inlet or outlet of say the rerceiver drier(best example) the that part is restricted and needs replacement as it is in effect acting like an additional expansion valve in the system..
Diagnosing A/c is the biggest gravy job in the buisness...if the system is equalized you need a new expansion valve, if the charge is good and no colsd air..you may need an expansion valve(tapping it will temporarily open it usally)
if the pressures are wildly off in relation to each other, there is a blockagge in the hoses or condenser/evaporater...normally cause by the receiver drier dessicant breaking up.
Good system performance is very easy to get...just make sure if you have a car tthat has no ac for a while to replace the drier(it is like $25-50) as that is one of the key parts that make it work right

KuHL 951

Good info Nick. Thanks, I've been cobbling AC work on my own cars on a DIY basis for years.I learned a few new things in your last post. All of mine are running cold this Summer but I'm down to my last 3 cans of R-12. I see a Mexican DuPont R-12 Road Trip coming up this Spring for sure. Thanks for the great info!

Mike B

Great info Nick...thank you!