07 Chevy Uplander heater wont blow any heat at.

Check coolant level first. Low coolant levels will not deliver hot water to heater core therefore no heat.
If coolant level is ok, check heater hose to see if they are hot when the engine is at normal operational temperature.(Both should be hot to the touch)
If so, then maybe suspect a blend door actuator problem.
If not, suspect clogged heater core.

Let me know