If your thermosat is stuck shut your vehicle could over heat and you will probably loose heat in the passenger area meaning you defrost will not blow heat.
If it sticks shut, it will block the circulation of coolant between the engine and radiator causing the engine to overheat.
If your main gas valve is stuck in the closed position, it must be replaced. This condition is the reason your thermostat will not cause the main burners to light.
Sounds like it's stuck in the closed position
1. water pump failure 2. thermostat stuck in the closed position.
Could be, low on coolant (a leak in the system), a stuck closed thermostat, a faulty temp gauge sending unit, a bad head gasket or cracked head (worst case scenario).
A stuck closed thermostat can lead to severe overheating which can lead to severe engine damage which then leads to big money for repairs.
the one possibility that i can think of is that your thermostat is stuck in the closed position not allowing the water to circulate threw the engine
Stuck closed thermostat. Replace the thermostat.
Overheating if stuck closed, no engine heat if stuck open.
Possible causes: low coolant level; thermostat stuck in the closed position; faulty water pump.
A thermostat can be stuck open or closed. If the engine runs to cool it is stuck open. If the engine is running hot it is stuck closed. If you don't have these problems you should'nt have to change it.
If it was stuck closed the engine would overheat soon after starting up, probably within 10 minutes.
The car's thermostat is bad and not working. Most likely the thermostat is stuck open. Thermostats are heat sensitive valves that open and close. If stuck in the open position the car never warms up. If stuck in the closed position it will over heat. http://auto.howstuffworks.com/cooling-system8.htm