1996 jetta 125,000 mi. Car runs great,with the ac on I have no fans working on speeds 1,2,3 when i go to speed 4 the ac light goes off, some cold air comes out for a few seconds and then i just have outside air blowing into cabin. I turn fan to 3, ac light comes on,compressor engages, but fan stops working, click back to 4 fans comes on A/c light goes out and i get cold air for a few more seconds. Any ideas ?