The car heater is blowing only cold air in my Hyundai i20. I have run the car over a long distance but the air is still cold. Any suggestions please?
This is typically the result of one of 3 things.
Low coolant - coolant is low, so it is not circulating through the heater core
Bad heater core switch/valve - There is a valve that controls how much coolant flows through the heater core. You might be able to watch this as someone adjusts the temperature setting in the car.
Clogged heater core - The heater core is clogged and not allowing coolant to pass through. This will require the heater core to be flushed, and possibly cleaned. Some people will pour in chemicals (like CLR) and let them sit in the heater core for an hour to eat away at any corrosion.