I have a 2000 Jeep Cherokee with 121,000 miles on it. Recently the heater stopped blowing hot air. Thermostat has been changed,water pump is new,hoses are hot,blower works. Radiator has been flushed and refilled.Has anyone had problems with the heater core being blocked or any other suggestions.

have you checked the valve on the heater hose? it could be stuck shut. I'd check that before I messed with the heater core

Where is the valve on the heater hose located?

just follow the hose from the water pump to the heater-core, you can't miss the valve, it's the only one on the hose.