When you let it run for 5 minutes, did you have it in gear with the Park Brake OFF, did you? :dontknow: .
The air compresor in the ACS won't run if the Spyder's not running, in gear, & with the Park Brake off - and even if all that
is in place, many (if not all?!) Spyders with the manual
AND automatic ACS (ie, those Spyders that also have a 'Hard/Soft' switch that lets the operator add or release air pressure in addition to the Auto Pre-set system) will report a fault & flash '
Manual' whenever the switch is activated on an empty air bag - apparently there
NEEDS to be
some air in the air bag or the system will report a fault & call on the operator to manually add some air pressure to the Air bag, just to be sure, to be sure!
As for the change in height of the hitch - if it's an OEM Hitch, then the hitch itself is fixed onto the end of the swing arm, so the air pressure that will vary
it's height
the most will be the pressure in your Spyder's rear tire!

. The change in height you measured as described above will most likely be due to the pivot point end of the swing arm on the frame (ie, the
other end of the arm to the hitch... That swing arm pivot end is the end holding the frame & weight of the Spyder off the ground by the wheel & axle & the air pressure in the tire

) going
DOWN as you emptied the air bag. The height variation you saw at the hitch end was the swing arm/hitch assy acting as a simple lever (ie Load on one end; Fulcrum being the axle in the middle under the Lever; Force pushing down on the other end to the load... ) with the 'Force' in this case being the weight of the Spyder pushing down on the Swing arm pivot end; the Fulcrum being the axle held off the ground by the wheel & tire air pressure somewhere in the middle of the Swing arm/hitch assy, aka the Lever's total length; and the Load end (ie, the hitch) being raised as the Force pushes the other end of the Lever (at the Swing Arm end) Down! Juuust like a see-saw/teeter totter - one end goes Down, the other end goes Up cos the Fulcrum is innthe middle! :thumbup:
In your case gunner, as you've described above, the hitch height change is pretty much exactly what you should've expected by measuring the hitch height; and I suspect the issue with the compressor not running is that you didn't have the Spyder running, in gear, and with the Park Brake OFF... this catches everyone
at least once!
So I'd suggest that you measure height changes on some other part of the body or mudguard, somewhere that's
carried by the suspension, not anywhere that's carried
only by the wheel, and that you start with at least 10 psi of air in the bag. Start by adding some via the Schraeder valve under the seat if necessary and checking the air bag pressure with an independent gauge so that you
know what it is/it's at least 10 psi; measure the '
suspension carried body height' as outlined; and then go for a ryde of a few hundred metres or so before coming back to your start point & returning the Spyder to it's original position; where you should re-measure the body height and the air bag pressure.

hyea:
THEN tell us what you've found... :thumbup:
Edit: 
pps: Sorry chris, I didn't check for any replies made while I was drafting mine, which ended up taking a fair bit longer than originally expected due to unavoidable interruptions.
