smoke coming out of dash vents

Need a bit more info. What color and, or, what does it smell like?

The most likely possibilities:

The heater core is leaking and fogging the windshield and sending coolant vapor out of the ac and heat outlets. This should smell like anti freeze. The fix is just change the heater core.

There are leaves or similar combustible trash that fell in the cowl vent, got into the heater/ac box far enough to land on the blower motor resistor, and when you run the fan, they burn and the smoke comes out the vent outlets.
I have had this a couple times, since I park under pine trees at home. This may give a lot of smoke and will smell like burning leaves or paper. Can cause major panic. It usually burns the stuff up and it's over with. Or, you can pull the blower resistor and clean it. I pulled over for this two weeks ago.

The ac evaporator core is leaking. With the compressor running it is discharging a cloud of refrigerant out of the vents. R12 will give you a white cloud, I am not sure what 134 does. It will stop when it is out of refrigerant, and may coat everything with refrigerant oil. Messy.

Your ac is too cold, or, for some other reason, it is condensing moisture and carrying it out of the vents when it is hot, humid and the ac is on. This can happen if the ac gets low on refrigerant, as it will get to a lower evap pressure quickly. It will also happen if the ac condensate drain tube gets plugged, as water will collect in the bottom of the ac case, and the air flow will start carrying it out the vents. If it collects enough, it will drip on the floor. Annoying.

Post a bit more info if you need further help.

I had this same problem and it was the heater core. If you have the car running for a while and then you turn it off, listen to see if you can hear any noises from under the passenger side dash. I could hear mine steaming and raising a ruckus which further confirmed the heater core theory. Good luck!

when that happened to me a few weeks ago...i found out it was an electrical fire under the dash. be careful

The steam will have a sweet smell to it if it's antifreeze. Hold a cool object over the vent until the smoke begins to condense on it. Run your finger over the condensationa and give it a taste. Sweet taste?...Anti freeze. Don't worry, one drop won't hurt ya'. I suspect it's the heater core. If it was an electrical fire, you'd know the smell right off. Burning rubber and plastic can't be mistaken for anything else.

true. it was still pretty scary....i had to hose above my pedals to put it out. It was scary enough to mention.

Is it after your burnout, I have the same problem tire smoke just seeps in everywhere, Seriuosly though, Like the others said the Heater core sounds like the culprit. And its not too fun to change out either.

Now that you mentioned it....why does the tire smoke fill the hatch and car so much/easily

Well contrary to what we might think are cars are not totally sealed with all doors shut and windows up, there is small uneven spots in door moldings and hatch mouldings that let it in as well as breather holes in the hatchand under the car, escpecially bad whe your siting in one spot for more than a few seconds, I know in the back of mine the rubber grommets thatplug certain holes in the floor are missing so that doesnt help. But part of the fun is smelling the smoke and the burning of the eyeballs...

If you have ever removed your carpet you will see many holes that smoke can get thru...

On the coolant smell and whether it is from coolant or not, I would open up your radiator cap and take a whiff of it (when the engine is cold) and smell it so your familiar with the smell.

heater core

I just went through the same thing, If you want yo8 can do what I did if you don't have the money to repair it...just bypass it.

WhiteThunder said:

I just went through the same thing, If you want yo8 can do what I did if you don't have the money to repair it...just bypass it.

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A new heater core is like $15 at Pep Boys. Just takes like 8-10 hours to install.

rd said:

The ac evaporator core is leaking. With the compressor running it is discharging a cloud of refrigerant out of the vents. R12 will give you a white cloud, I am not sure what 134 does.

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Dude no offense but horrible advice. He should not be discharging r12 into the atmosphere.

My guess would be heater core, are you getting any film on your windshield?