Hi, my car is 98 accord LX, 4 cylinder. It runs great. After an oil change last week, I noticed hot air coming from dash vents when the car is running. If turn on A/C, hot air is gone. A/C off, hot air comes. I turn Vent on, no hot air. Vent off, hot air comes again. Even when the outisde air is very cool. Anybody know what might be the problem?

There was cold air flowing slightly from the vents before the oil change. Like A/C is on but either A/C or Vent is off.

 

sounds normal to me.......

dont want air coming from the outside set ur temp control to Cool side not Heat side and set it for recirculation!

 

Thanks. I did tried to keep A/C Cool side on for two hours yesterday. After A/C was off, hot air kicked back. I am worried the hot air is from engine and may contain carbine monoxide.

 

That is regular behavior to an extent.
For example, if you have the heater/AC not blowing anywhere in the vehicle, but you still have the notches up (1,2,3,4) your car is still going to blow in air.

Sooo--basiclly--your going to be blowing air thorugh your vehicle almost all the time.

You really only have a problem if your vehicle is blowing hot air and you have the A/C on, or vis versa. Otherwise, you're ok!

If that is the case, it's most likely your A/C just needs more fluid, or it needs to be recharged.