If the compressor seems to be locking each time, it might be slugging liquid refrigerant. There is the possibility of an overcharged A/C system, air in the system, a plugged orifice tube, or all three. The only way to check is to evacuate the system and weigh in the correct amount of R134a.

 

Actually those numbers are a little low...ambient temperature plays a big role in what the pressures will be, and on a R134a system, the high side can often be up to 250psi on a humid 90+* day. The low side will usually be between 30-40 psi when operational, and static pressures can range from 75-90 depending on ambient temp. When reading R134a, or R-12 manifold gauges, you should have the engine running between 1200-1500 RPM for accurate readings.

If there was too little R-134a in the system, the compressor would either cycle on and off constantly, or not at all. If overfilled, the compressor may get slugged like Mike suggested. If way over-filled, the high pressure switch will not allow compressor operation at all, or may quickly shut it off.

In our shop which is generally around 70*F, I usually see 30-35psi on the low side and 200-225psi on the high side with the engine running at 1500 RPM.

 

they have been cleaned with no affect. there was no change in conditions when i put a ported/polished tb on either.... i have check high and low side pressures and they are good as well, but the last time i drove my truck for more than 1.5hrs, the a/c started blowing a little warmer than usual. So i would need to evacuate the system and do what else to check for a plugged orifice?

 

When you weigh-in the correct amount of freeze gas, according to the label on the truck, the pressures will tell you if the orifice is clogged. If it's clogged the pressure on the suction side will be way too low, maybe even in a vacuum. That is when Mr. Goodwrench replaces the orifice tube and starts over, and Mr. Shadetree keeps dumping in more refrigerant until the suction pressure looks reasonable.

 

I would replace it any way. Just about every system I have taken apart for service it is usually dirty... doesn't mean it won't work but for the small amount of $ they cost and the 5-10 minutes it takes to change it, why not.