Vauxhall Zafira blower

Sounds like heater motor ballast resistor knackered .

I guess that by now you may have solved the problem. If the blower motor runs, but you get no real movement of air it can be down to a blocked cabin pollen filter. To replace the element you need to remove the glove compartment to access the blower unit with many clips around a narrow, vertical,removable panel that gives access to the element. Good luck.