on max a/c air blows out floor vent hard, weak from dash vents; floor vent blows on all settings except defrost..
the diaphragm at the floor vent works as it closes it on defrost mode; what
component would not be closing it on other modes like max a/c?
check for a broken vacuum hose..
They use a blend door motor, its most likely weak. Make sure the linkage isn't broken. It's under the driver side dash towards the center.
Search Chevrolet C/K 2500 Questions
Are you a UK consumer? CarGurus now has a discussion forum in the UK.
Chevrolet C/K 2500 Experts