I just need to debug WHY a central vacuum cleaner
has low vacuum suction at the hose.
https://c4.staticflickr.com/8/7500/1...7989dca3_c.jpg

I snaked the hose itself, and it's not clogged:
https://c4.staticflickr.com/8/7573/1...fb4ff8bd_c.jpg

Strangely, it seems that the vent to the outside has plenty
of outward force, yet the vacuum hose has almost no suction.

If there is a hole or a clog in the wall hoses, I don't know
how to find them. Is it normal, for example, to snake the
wall holes?

The container, in the basement, is not clogged, and seems (by
sound) to be running at speed (no abnormal noises).

I haven't taken it apart yet (it's in a nasty cramped space),
so, I ask you guys if you have any experience debugging why
a central vacuum would have:
1. Very low (almost zero) flow at the wall, but,
2. Decent air flow to the outside of the house.