Some observations on the autopilot and flight director.
I tried making an ILS using the autopilot and flight director.

I vectored myself well outside the outer marker for a 30 degree intercept for the LOC and level flight at 3,000 feet. Autopilot set to altitude hold and heading select.

I selected G/S AUTO which should intercept the LOC first then the G/S from below. Heading select did not trip off to intercept the LOC. I took off heading select and the autopilot then started to capture the LOC.

The autopilot flew the ILS as expected after that. The flight director which was also selected to G/S AUTO on the other hand did nothing but follow the ADI.

G/S AUTO should be used to intercept the ILS when below the glide slope. Using G/S MANUAL will cause the autopilot to intercept both the LOC and G/S right now! G/S MANUAL is used when you are above the glide slope or when you are already on both the LOC & G/S. In older 727's this would EXTEND the glide slope and re-sensitize the G/S signal if on a long final. As you approach the runway, the G/S signal is desensitized by the auto pilot so as to lessen the pitch movements as you get closer.

Don't forget this is 50 year old stuff! The newer planes are MUCH more advanced and make wonderful auto-lands. I have made many auto-lands at very low RVR's in 767 and 757's that were flawless. The 727 is not such an animal and the auto pilot is, shall we say, old.

Success with the auto pilot in the 727 requires giving the old gal smooth intercepts - around 30 degrees, and being on speed for the flap setting so as not to cause large pitch changes.

I hope this helps.

Lou