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I turn on the AC when I start the car and start driving, no smoke.

I get on the highway, drive few miles maintaining 70 mph, turn the AC off for a few minutes and turn it back on, I see white smoke coming out of the vents. There is no smell to it. It goes away in about a minute.

What could be the issue? Heating core? Coolant leaking? something else?

 
Rep Power: 518

It's not smoke.
It's water vapor.
Normal. Nothing wrong.
You just got it into a situation where you can see water vapor.
Same water vapor that makes up a cloud.

 
Rep Power: 257

once,white smoke came out of my acuras vents after the head gasket blew out. i don't remember if it had a smell though.

 
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If there is no coolant smell, then it must not be a failed heater core leaking coolant.

 
Rep Power: 518

A thought: You're more likely to witness this vapor phenomenon when using fresh air instead of recirculate.

 
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Thanks for the responses. This never happened in the 11 years I owned this car though.

The "recirculate" mode is always on when I turn on the AC. There's no smell and the smoke/vapor dissipates in about a minute. But it comes back when I turn the AC off for a few minutes and turn it back on. I haven't noticed this issue when I'm driving on the local roads where the speed limits are low.

 
Rep Power: 518

Still normal.

 
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I have an 01 LX. The first time this happened to me, I totally freaked out. I actually did not see much on-line about it either. It used to happen a lot. I never took the time to troubleshoot the exact conditions. But, it seems to have gone away and hasn't happened in years. I had actually forgotten about it until seeing your thread. I am glad it is considered "normal" :-).