1999 Jeep Cherokee heater

I have a 1999 Jeep Cherokee with 200,000 miles on it. Bought this Jeep new and it has never has really "hot" heat. The only way to get heat on the floor was to back off the climate control knob a couple of notches (not full heat) and it would switch to the floor and heat some. Water pump went bad and I installed a new pump and thermostat at the same time. Now for the problem. No heat out of the vents. Engine comes up to temperature and all seems well, just no heat out of the vents. Floor, defrost, or center. Just cold air. Tried all the usual tricks like backing off the climate control and slowing fan speed down. Nothing but cold air. Every once in a while all the air stops coming out from the vents but I can still hear wind noise in the dash. Sounds like a hurricane in the dash but it doesnt blow out the vents. Slow the fan down to low and then it starts coming out the vents and you can turn the fan speed back up and get plenty of air blowing. Just no hot air. Any ideas? Any help would be greatly appreciated.