Larry,
When I first got my H3, I thought I had a malfunction with the same seat.
Turns out, it’s just really temperamental.
From memory, the first lever, closest to the front, either locks the air in or completely dumps it. The second lever provides some cushioning.
The third or fourth lever is the tricky one. You need to adjust it just slightly to add air; otherwise, the seat will either come up a bit or go all the way up. It’s like filling a balloon halfway—too much air, and the seat pops to full height.
For the cost of that seat, it shouldn’t be so finicky!
Hope this helps!
Mike
…and no, I don’t have a manual.