Just thought I'd share this

Aircon was not working on my 2000 V70 classic - mate who's an aircon
engineer topped it up but it hardly took any - still not working.
In the meantime I bought a OBD tester/reader/eraser from eBay for my Jag XJ
sport - plugged it into the Volvo to see if it would communicate, it did and
came up with a code that corresponded to an aircon sensor pressure fault -
reset the fault code and hey presto!!! working aircon and it's been ice cold
for over a week.

Just in case you are chasing a gremlin in your aircon - check the OBDII
faults,

Cheers,

Steve