Not sure what a 1624 Selector is but have Adjusted many 2 SP AC's with 6850 Selectors and Odd/Even Floor Vanes. The basic slowdown rule on any of the 2 SP AC's slowdown distance is 3 inches per 10 FPM of contract speed. If it is slowing down at other intermediate floors ok then it is probably the distance not long enough.

6124 is model of selector not 1624. it is older and very different then the 6850. there are no pie plates just a carriage, shorting bars and contacts.

Anybody?

Get the controller data tag info with the wiring diagram number. I may have prints for it!

i also have a good generic print, shows all the nomenclature for the relays. looks like hi speed should drop when you get "S" to reset off of the uhs or dhs contact on the selector. S appears to be a set reset relay, similar to the pm relay on the 6850 selector.
at least you could check to see if hi speed relay P is dropping at the right time. or maybe it has something to do with the self holding circuit of A and B. it appears that 1MS and 2MS selector contacts control the actual dropping of direction relays A and B as long as X the auxiliary stopping contact is out. with the print i have and a little time in front of the controller, you should be able to figure it out. pm me your email address ill send it over

here is how i see it, S relay picks up with a direction A or B, Hi speed relay P picks up when S picks, the car runs hi speed until the UHS or DHS brush hits the floor bar contact of the call that was placed, this in turn resets S relay, which drops out X relay which in turn Picks up Q the slow speed relay, Q picking up drops Hi speed relay P, the car runs on the slow speed winding until 1MS or 2MS contact opens which drops the direction relay and the car stops. think of 1MS and 2MS as the level up and level down switches. could be a sluggish reset of the S relay.