...fan runs on both speeds, my problem is that when the a/c is turn on the aux fan should come on too and it does not.

Ed,
I think the AC activates the K1 relay. So it runs the aux fan at low speed. When I got my car the PO had the wrong type of relay in the K1 position so it burned out the ground trace on the back of the fuse board. This ground trace was also used for some other doo-dads according to the mechanic who found the problem. Fixing it made the car run better.

Thanks for your response, I changed the K1 relay with another one in the fuse box; they have the same part numbers but it didn't work either.