Like the subject says, how many psi should I be showing with a guage on the low side (the one that gets cold I guess) port on the A/C hard line?

My car isn't blowing cold anywhere near idle and I am wondering if I am low on R134a, but when I hook up a guage it seems to run in what the guage has marked as yellow/red.

 

Well, for an R-12 system you would want to be running 35-40psi on the suction side and about 225psi on the high side. I'm not really sure if R-134a runs at different pressures but it might.

-Rob A.

 

You should be 30-34 low side and 175-225 on the high side.

Also, your condenser fins my be clogged with dirt prevent good airflow.

 

I am not sure what to think. If I sit at idle and rev it up to 2500 rpm or so and let it hold there, I get cold a/c. If it idles, I don't. Moving, not moving, makes no difference, below 2500rpm makes no cold air.

 

Either one or two things...
You are low on charge, or there is blockage in the orifice.

 

Where is the orifice?

 

It's inside the "block" ( the square block where the lines go into the evaporator unit). If you remove the large line fitting, you will find the orifice there. You will have to evacuate the unit of refrigerant charge before you can do this.