my truck heater will not heat. on 1996 Chevrolet 3500 Pickup

Installed thermostat with a 195 degree temp.Replaced water pump and coolant. Ran water threw heater core, both sides. still no heat to heater core. both lines to core cold. warm day ran truck for 30 min got engine to 200 degrees still lines to core cold. radiator nice n hot. don't see coolant circulating back to radiator from heater core.

Asked by for the 1996 Chevrolet 3500 Pickup
i think you have a heater control valve inline with heater hoses ck to see if its stuck closed
Thank you for your help. I did find the problem this truck had a different engine than the original and the guy who insalled it routed the heater core wrong. once again thank you for your help.
thats what we are hear for I am glad you found the problem
1 more answer
sounds like a bad t stat but try to bleed system first