A/C blowing cool not cold...

Uh, ?? what's wrong with feeling the heater hoses and see if they are hot?

Nothing, but it doesn't give you much info. Shutting down the flow can tell you if the ac system is working well without any additional hot water in the system.

In the time it takes you to touch the hose, I can completely eliminate the question of water leakage through the valve with a pair of vice grips. It's an old AC shop trick. And if I'm stuck out on the road with a bad heater valve, I can drive home nice and cool.