I have no heat on 2001 Chevrolet Blazer

The ac works fine and there is no leak in the heater core

Asked by for the 2001 Chevrolet Blazer
Have you ever removed that red 'crap' it came from GM with called Dex-Cool?
Yes I have replaced the Dexcool. I have heard this stuff will settle in the lowest point and solidify.
Possible stuck open thermostat, low coolant level, heater controls or restricted heater core. Replace t-stat first thing anytime there is a heating/cooling problem with the engine which also affects hvac systems.
I have done all of the recommended except replacing the core., I am about to use air pressure to blow out any clog.
If it is restricted, i have good luck with air and water together with a rig i made up. Try the air, cant hurt.
I ran water through it. It flowed fine in one direction but not the other.
I was wondering it there is some find of check valve in the system that would
prevent the flow in one direction?
Not that i am aware of. Hook hoses back up, refill rad run until hot and see if both heater hoses get hot. Post results.
I ran the motor to running temp. The big radiator hose was to
hot to touch but both the heater hoses were barely warm. I had no problem holding
Them in my hands. I held them close to the firewall.
addendum : I ran the air pressure up to 100 lbs. It blew out something,
Because I now have heat. Thanks tor the support.