Bongo Fury

Had a bit of a scare yesterday, smoke started coming through the vent in the passenger footwell.
It only happens when the aircon is on, I guessing it might be the heater fan motor.
We haven't used the air con for a while due to rain.
Has any one else had the same problem?
Need to work out what bits need replacing and where to get them.
Any advice gratefully received.
Thanks
Garry

Lift the bonnet, remove the plastic air intake from the fan assembly, can you turn the fan? If the answer is no or yes but very stiff then remove the fan assembly and lubticate the fan bearings.