I would call someone who is used to dealing with thermostats and repairs to come look at it before you buy a new one. They should be able to tell you if it's fixable and how much it would cost to fix.
You'll need to be far more specific. What sort of heater? What kind of controls does it have? Thermostat settings?
You need to replace the 2 shocks that are on it. They are what keeps it opened.
you need to replace the window regulator
It is programmed by the people responsible for maintaining the light.
Assuming that your gauge is accurate, then you probably have a stuck thermostat in the open position that is not allowing the coolant to stay in the engine long enough to reach proper operating temp. Replace the thermostat or have a good mechanic do it for you.
replace the a/c thermostat
Your thermostat is broken
You need to replace the DRL (Daytime running light) Module
It sounds like you may need to replace your thermostat. Even though you have enough coolant in the radiator and overflow reservoir the coolant may not be circulating through the system because the thermostat is not opening. When the coolant can't flow through the engine and radiator it will get very hot and stay very hot. This is usually an inexpensive and fairly easy fix, just purchase a new thermostat and install it or have a mechanic do it for you.
Its most likely the thermostat stuck open, i.e gone faulty. Quick and easy fix. Failing that replace the the coolant temp sensor, again quick easy fix.
Hard water, and calcium can build up insite the hoses and get released in chungs during the flush process. These pieces can get caught in the thermostat and cause it to fail. You can try removing the thermostat or just replace it as it is an in-expensive part. You might consider re-flushing the radiator as more calcium might hit the thermostat after replacing it.
If they turn on but don't blink, you probably need to replace the signal flasher relay.