I faced same issue of tripping of compressor on and off when on idle or upto gear 2. but when running on gear 3 or above, there was perfect cooling. even at gear 5, I have to switch off ac for some time. mechanic suggested to change the gas. one mechanic said weak compressor and radiator. I changed the gas but same problem existed. I thought about possible reasons. Dollowing points came in my mind.
1. Upto gear 2 extra load is on ac. When speed increases, load on compressor decreases.
2. Tubes of radiator or chocked,compressor is weak, replacement of radiator or compressor may be required.
But engine was not overheating.
For solution,before going for major work I thought of a layman option. I made radiator fan to start directly . It means radiator fan sensor wire is cut down. Now fan starts directly whenever ignirion is put on.
It is under observation since last night. At night its cooling was perfet even on idle. At 1600 hrs, I again checked. There is perfect cooling at idle,and even at all speeds.
Conclusions. From this I concluded that cooling is improper when radiator fan is on auto. When cooling is improper phase change of gas does not occur perfectly which results in extra working of compressor resulting in frequent tripping of compressor. As I had already serviced ac system so it means either coolant change is required or condenser tubes cleaning is required.