heater won't get warm in the car

[thejack]

Originally Posted by Jamesp

Warm the car up and pull the plastic battery cover in the Frunk - check the two rubber lines behind the battery - if both good and hot then heater core functioning. If not bleed the air out of the cooling system.

If both hot, a mechanical failure in the mixing valve / door is likely.

It most likely depends on bad mixing valves. Find the exchanger valve (hot/cold) and check if it moves as long as you increase/decrease temperature. If the valve's arm moves smoothly but no warm/hot air comes out from the grids, take it down and replace it. You can even try to repair it if you have will and skill.