Have you flushed the heater core?
What temp. thermostat did you put in? Try a higher temp. one. or check to see if heater core is clogged
The heater might blow cold air in a 2000 Silverado because the thermostat is sticking and not changing from cold to heat. The thermostat is usually located in a hose that leads from the radiator to the motor.
Defective heater control valve or air in cooling system.
the heater core could be pluged or the heater control valve is stuck closed
i need to replace the temperature control light bulb on my 2004 silverado.
possibly thermostat stuck in the open position?
Most common things are Thermostat or a bad heater core but could also be something blocking the door down by the heater core. I changed my Thermostat and Heater control Valve to find out a pencil fell in the defroster and prevented the door from closing. Hope this helps.
the thermostat used to control the heater and after we select the four pole switch to some number the thermostat start connect the power to the heater at the same time the heater start to heat and when we select the switch to zero position the heater not work
Your heater relay switch may be bad
the heater control has a thermostat for the heater only. that thermostat needs replacing
I had this problem once with a different vehicle. You may check the heater control. That may be the problem. Hope this helps.
Heater core changed three years ago,I changed Thermostat Heater still blows cool air.