Ronny,

You say you are 10 to 15 miles out and then you descend to 1,500. If this is correct you are way below the glide slope at that point. If you select MAN G/S instead of AUTO G/S the plane will indeed climb since the glide slope is above and MAN G/S will capture both the LOC & G/S right now!

The standard glide slope is around 300 feet per mile, so at 10 miles out the glide slope is at 3,000 feet. Even if you were at 1,500 feet and had captured the LOC and tracking inbound, you could select AUTO G/S and capture of the glide slope would happen as the G/S needle centered.

Lou