Environment Controls Not Working On Driver Side

[jumbojake]

My 2004 Avensis has a full working air-con on the passenger side, but on the driver side, doesn't seems to work, or perhaps to a much lesser extent.

I assume it's a problem with environmental controls... but no idea where to start ... any ideas??

[FROSTYBALLS]

Have you checked the air con filter (pollen filter) in case it is blocked?

[jumbojake]

I only changed it a little while ago... it seems to be pretty clean, all LHS vents are ok, but all RHS are not tracking the temp setting... I assume some lever or thermostat isn't working