On Thu, 06 Apr 2017 08:54:27 -0400, opined:

Both of the two central vac units that I have owned -
diffferent makes - had an additional inlet at the machine -
if yours does - you coulld check IT for suction - carry your
hose to the garage.. and listen to the motor..
Also - if IT doesn't have suction - ta-da.

Inlets?

I never noticed if there is an additional "inlet".

There is an outlet for exhaust which is near the vacuum motor and which
blows to the outside of the house.

I guess I could take it apart and disconnect the main inlet hose though.

I'll look later on today when it gets light and see what I can see.