No heat and temperature gauge not working?

Hello,

If the engine is not warming up or the heat is not functioning (even will coolant at correct level), it could be due to a stuck open thermostat.
An open thermostat will not allow the coolant to reach operating temperature as it constantly allows the coolant to move through the radiator and keep it cool.

Here are a couple of helpful guides:

https://www.2carpros.com/articles/how-an-engine-thermostat-works
https://www.2carpros.com/articles/replace-thermostat

I have attached the thermostat replacement procedure below.

Let me know if you have any questions.

Thank you.