Are they certified or certifiable Volvo mechanics? They haven't worked on FWD drive cars yet?
A simple shorting of the pressure switch will try to engage the clutch. A broom stick tapped on the clutch should engage it if the gap is too large. A check of the engine fan relay is also needed, the fan needs to be running for the condenser to work.
This is not rocket science! It is a standard AC system.

If you have been adding lots of r134a yourself, you may have clogged up the expansion valve or the receiver/drier.

Also try turning the heater/blower speed up close to max. One of your cabin thermostats may be dirty.

Get new mechanics, but avoid the dealer! Any AC shop can make these fixes. Do not buy a new compressor. Your clutch is not old enough to justfy getting a new one. You can put the plastic shims in yourself, in less than 1 hour.

Klaus
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Please answer, we need to know if the advice is good or bad. The 164 has a new home, all I am left with are 2 turbos :)