Turbo SW. Just spent a good amount fixing all the O-Rings and regassing it (154a).
However most of the time the compressor keeps trying to kick in every 1-2 seconds or so (which causes the revs to drop if idling).
I can also hear a separate clicking sound from something right behind the glove box. Is there like a sensor or something else faulty?
 
Thanks.

On my wife's Camry there is a relay in the engine bay used to kick in the compressor clutch which was faulty. It's only a guess, but I'd check where the relay is in a SW20. If it's near the glove box it may be what you can hear.

Would it possibly be this?
88630RELAY ASSY, COOLER88630-95702 
 

Or possibly something from the front fuse box?

(2) or (3) or (7) ?
Cheers.
    

In the Camry it was part # 90987-02028 Relay, Magnetic Clutch in the fuse box in the engine bay.
I'm sorry, I don't know what the equivalent part is on a SW20 or even if it might be your issue, but the problem does sound similar.

Took to an electrician as I didn't have time to sort it, hour later he gave up looking for the fault lol. Least I didn't get charged for labor.
 
It's a intermittent issue as the A/C works sometimes, but it seems the car revs don't keep up enough to keep it on all the time. Such a pita, lol.

"It's a intermittent issue as the A/C works sometimes, but it seems the car revs don't keep up enough to keep it on all the time."
 
The engine revs are only increased by the idle up vacuum valve when the a/c is switched on, not the other way around.

 
A clicking sound may be the magnetic clutch relay behind the glovebox. (see pic).
But hard to tell whether that is the problem, and it is a PITA job trying to access that stuff behind the glove box.