OK here is what I am dealing with and maybe someone can give some insight on what to look for or what to do with this air conditioner system Older 1985 International Truck, was a r-12 system that someone supposedly removed the older oil and changed over to newer R-134a so here is what I did, when I started this the truck air conditioner compressor would cycle but no cold air, at one time there was cold air but that was last year. Now to today, I removed the old rusted out receiver /dryer and replaced it with a new one and replaced 1 new line that was bad and rusted. Before installing the new line and receiver/ dryer I removed the lines off the compressor and flushed the condenser and and the evaporator with a flushing agent for air conditioner systems, the blew all lines out with air until nothing was coming out . installed the new line, receiver/dryer, new o rings, and re-installed the lines on the air conditioner pump with new o rings. then vacuumed the entire system, low and high side for 45 minutes. Watched it for 5 minutes after to insure it maintained negative pressure before starting to load it. I started with a 6 oz can of ester oil and r-134a and noticed the pressure with the unit running shot right up low side 35 psi ,high side stayed low , pump would not engage. Added another 6 oz can of the ester oil with 134a and unit running but pump still would not engage, for some reason I was not getting power to the compressor unit? so I added 12 volt power to engage the pump manually while running to see if the unit would load any r-134a, the low side seemed as if it did not want to take the 134a, and noticed the pressure on the low side going to 80 lbs while the high side stayed all the way down to about 20 lbs? What would stop the power from getting to the compressor ? why is the pressure not correct? what turns the pump power on and off? I didn't see a expansion valve or orifice tube where is that hiding and could these cause the problems? I dont knwo why it would cycle before I did this stuff? and ideas I m showing some pictures , may be I can get a little help, thanks