The heat valve is stuck open.
You should check the thermostat and the fuse for the heater.
Under the radiator hose that meets the top of the engine under the throttlebody if you follow the heater hose from firewall on the driverside toward the engine it goes to the thermostat housing.
Could be low coolant, stuck thermostat, bad heater control head (if climate control)
Low coolant? Bad thermostat? Defective radiator cap? System air bound? Heater core plugged or restricted? Temperature control cable not adjusted properly?
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
you must be a wierdo.stupid.
Is coolant up to level? Are heater control cables functioning to their full travel Thermostat may be defective and opening too soon. Heater maybe either "airbound" and need to be bled or may be plugged
It could be the thermostat. Open up the radiator cap when it is hot and see if the water is flowing in the radiator. If it is not then it may be a thermostat.
Where is the heater core for a 2002 pontiac montana
A malfunctioning thermostat can cause your temperature gauge to go up and then allow the gauge to go all the way down. When the thermostat is stuck closed, your engine will overheat and water will not get to your heater core. When the thermostat opens the engine cools down and water flows to the heater core.
Check: Heater controls, doors & door actuators, thermostat could be stuck open, heater core possibly plugged, might have a water shut off valve that's not working (depending on what year).
The Pontiac G6 block heater is located on the right hand side of the engine. The block heater can be located by following the block heater cord.