I have just installed a replacement unit for my Heater/Air con/Fan speed control panel (with the lights changed to blue) and have now run into an unusual problem... The dials seem to have changed function. Vehicle has the standard temp controls, not the climate controls and have the same issue when the I reverted back to the original Heater/Air con/Fan speed control panel.

Here's a description of what's going on...

Feet air vents - all functioning

Cool air forward vents, warm air feet- temperature control only controls feet vent, forward facing vents stay cool

Forward facing vent- when set to warm temp, front window demister engages with warm air, when cool temp is set, demister is still engaged with cool air and air speed increases from front window demister, sounds like vacuum leak from heater/fan control panel but cannot define exactly which tube sound is coming from. Nothing seems to stop this vacuum sound, when other vent directions are selected, vacuum sound disappears, but when forward facing vents are selected again, the vacuum sound increases as it releases pressure and then returns to a quieter vacuum sound.

Front demister and feet vents - feet vents work fine, air is flowing through front demister, temperature settings working.

Demister - works as per normal

I cannot see any loose or unconnected wiring or tubes and this has got me stumped... Any ideas?