Vauxhall Vectra Climate Control Intermittent Blower Fault?

Hi. I have a '98 Vectra CDX with digital climate control. The fan is only working every now and then. When it's blowing, it seems fine, can control the fan speed and temperature, but then it just stops blowing. You can hear it trying every few seconds (slight clicking - already changed the relay). Can anyone point me in the right direction? Many thanks.