I only wrote you my idea on the subject of the A/C that you started as a problem.

The things he said are not items connected to rapid cycling of the compressor. It is engaging and loading the engine.

When the A/C is cycling you should only feel the loading of the engine as it cycles.

Hesitation/jerking/chugs are more in line with what has been mention by Paul Driver of Inga. A over charged/plugged/moisture wet system.

If YOU only notice it with the A/C on was my clue that the mechanic "may" be doing "the customer dance". Guessing at what you are telling him to fit a symptom any where else. I admit, a mechanic depends a lot on the customer to tell him what needs to be fixed.

Then again you may have two problems. One exaggerates the other. The A/C changes the ECU mode. It effects idle speed. Loading effects timing.

If the A/C load or cycling is out of ECU program load perimeters, there could be symptoms of possible "shuffling" of a whole lot of the engine controls.

A mechanic in business should be all you mentioned. He should know that this is a GM A/C system. Charge weight is critical for proper operation. Orifice or capillary tube systems are charge critical.

A refrigerant leak or air and even a drop of moisture can change its pressure behavior quickly as Paul tries to put in his post.

It appears that you have been fighting that A/C system with a lot of parts changing. My thought or idea is. How Come?

Its a straight forward simple system and probably the best Volvo has used in all the years. Except the 850's on. They got leaky tubes in their evaporators that dealers ignored when ever possible!

I don't like the climate control complication. Having to adjust something is a good thing to keep you alert/awake otherwise, it drains your pockets.

Since you are on the brick board you are going in the right direction. Learning how to describe the problems with a vocabulary that you will learn by being involved in the car world around you.

Decide, A/C always or not and think with us. You'll have the fun we get in the process.

Regards!