1999 Chevy Blazer What and how much

What you need to do is to let your engine warm up to normal temp and feel both of your heater hoses they should both feel the same as your radiator hose. If you have a problem with blockage in your heater core or anywhere else then one or both of your heater hoses will not be hot. If one of the hoses is not hot you should unhook both of your heater hoses and hook a water hose up to one of the tubes going into the heater core and run water through it if water barely goes through it then you need to replace your heater core. If the water starts flowing freely then hook everthing back up and see if you get warm air. The next step is if both hoses are hot then you need to go under the dash and work the heater control from hot to cold and find the blend door that is what directs how much air comes through your heater core and how much goes through your evaporator. Start looking behind the glove box in that area anyway where the heater hoses hook into the heater core go to that area underneath the dash on that blazer you should be able to remove the cover of the heater core pretty easy and feel it see if it is hot then you should have heat you should at least be able to hear the door move when you change it from hot to cold once you have done a few of these test let me know what you find and I will help you from there