1990 xj6 air blower

Could be your blower is not working. Check the fuse first, then go on from there. There should be a fuse only for the blower.

Set air con to manual and turn fan to max, you will sure hear if the fan is working then.

If it is then you need to start looking at the vacuum pipes that control the air flow to the different vents. Try playing around with the air distribution control - do you get air to the windscreen vents? is it only via the floor vents, which of the dash vents does air not come from etc, this will help you to narrow down where he problem lies assuming of course the fan does work.