Car does not get warm

I have an old Toyota Camry Wagon 1990 with ~180K miles (original owner), well serviced and runs nicely. A few days ago I noticed that it no longer gets warm inside the car. When I turn on the heater it does not work. I only get cold air and I am freeeeeeezing when I drive. Does someone know what part needs to be replaced so it gets warm inside de car?

If this happened SUDDENLY, it likely means your air door is stuck in the outside air mode, and you are getting ambient air on your feet. It could also mean, but less certain, that your thermostat is stuck in the open position. I would have a technician look at these two first.

If it developed slowly, your heater core is likely plugged and no warm coolant is coming through.

When the engine is cold, check the coolant level in the radiator and the overflow reservoir. The radiator should be full right up to the cap and the reservoir should be partially full.

Is the engine reaching the correct operating temperature, and does it warm up quickly? If not the problem is likely to be a faulty thermostat. If the engine doesn’t warm up you’ll get no heat, or little heat, and also waste gasoline.

If the engine is warming up you have to determine whether coolant is getting to the heater core. If the coolant isn’t flowing through the core there’s no heat. A clogged heater core or inoperable heater valve (if the car has one) could restrict coolant flow.

If the heater core is hot the problem is with the blend door inside the car. The blend door directs air through the heater core or around it, depending on the temperature setting. If the blend door is stuck in the “cold” position it will not direct airflow through the heater core.

If you change “regular” green coolant every 2 years and the thermostat every 4 years this kind of problem won’t happen.