Why does the car vent suddenly blow hot air?
2 Answers
The reasons why the car vent suddenly blows hot air: 1. The external circulation is turned on, as the incoming air passes through the engine compartment and carries the heat from the engine into the car through the air distribution box, causing the vent to blow hot air; 2. The car's heating system is turned on, leading to hot air from the vent. Simply adjust the vent's circulation mode or turn off the car's heating system switch. It is normal for the vent to still blow hot air after turning off the air conditioning. After turning off the air conditioning, just set the temperature to the lowest and switch the air conditioning to internal circulation mode. The car air conditioning cooling system consists of a compressor, condenser, receiver-drier, expansion valve, evaporator, and blower.
My old car had the same weird issue last week—suddenly blowing hot air from the AC vents while driving. The mechanic later told me there could be several reasons: the most common is the AC system automatically switching modes, like when it’s set to 25°C but the outside temperature drops to 20°C, so the computer decides heating is needed. Or maybe you accidentally bumped the temperature knob and turned it up. Another possibility is having the recirculation mode off, letting hot air from the engine bay seep in. The worst-case scenario is a stuck blend door, stuck in the heating position. I’d suggest first checking your AC settings and recirculation mode yourself. If that doesn’t fix it, head to the shop ASAP to inspect the blend door actuator—driving in summer without cold air is unbearable.
