Although winter is almost here and heat will be my friend, during the summer months the constant heat from the heater core sucks. My blazer originally had AC, but was removed sometime in its 28 year life. It now sports only floor heat or defrost (no side vents even). I would like a way to stop the coolant flow to the heater core in the summer, but be asily opened back up for cold mornings etc. Is there a easy way to do this?