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Smoke Coming Out of Defrost Vents


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On my 97+ truck I recently noticed smoke coming out of the Defrost vents on the dash (side vents only) after driving it for a little while.  It doesn't smell like anything at all, doesn't seem to matter if it is hot or cold outside, and is so little smoke that you can barely see it when the truck isn't moving.  It doesn't get any worse as time goes on either, it stays the same amount of smoke the entire time. 

 

My first thought was a leaking heater core but I have dry floors and even the drain valve in the engine bay never seems to be wet. 

 

The blower motor is a little noisier than my XJ but it seems to work just fine.  

 

Any ideas? 

 

Edit: forgot to mention that when the blower motor runs, the smoke goes away.  It's only there when the blower is completely off. 

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Yeah I do but I'm worried about the noise in the blower motor.  I'm thinking there may be crap in the hvac box.  I'll pull the resistor and blower motor out when I get time and look around for anything. 

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3 hours ago, cruiser54 said:

Rodent nest in blower motor cage?

 

That's what mine was. 

 

Don't have that issue, but I had a Honda CRX years ago that had a mouse baked to the valve cover. I can't be sure, but that car seemed a bit sluggish after that! :laugh:

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7 minutes ago, kryptronic said:

This happened on my YJ.  The cowl drain was clogged and when the heater was turned on the trapped water turned to steam.  

I'll check that too.  See whats weird is that even if I don't turn the blower on at all it still smokes after a while. 

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43 minutes ago, Dzimm said:

I'll check that too.  See whats weird is that even if I don't turn the blower on at all it still smokes after a while. 

I mentioned it because I had a similar problem that I feared was catastrophic, and turned out to be caused by 25 years of dirt accumulated in a plastic drain tube.  When it happened to me, it was a distinctly white cloud of what I thought was smoke.  I feared something caught fire.  No smell, obviously, it was steam.

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43 minutes ago, kryptronic said:

I mentioned it because I had a similar problem that I feared was catastrophic, and turned out to be caused by 25 years of dirt accumulated in a plastic drain tube.  When it happened to me, it was a distinctly white cloud of what I thought was smoke.  I feared something caught fire.  No smell, obviously, it was steam.

Yeah I'll have to look into it.  It would make sense to be some kind of steam.  I don't remember it condensating on my hand or anything when I was first investigating it.  Did it condensate for you? 

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7 hours ago, Dzimm said:

Yeah I'll have to look into it.  It would make sense to be some kind of steam.  I don't remember it condensating on my hand or anything when I was first investigating it.  Did it condensate for you? 

Not that I recall.  It didn't fog the windows up either.

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  • 3 months later...

I had a similar thing happen in my 91. I first noticed it once daylight savings hit and thought it was my headlights smoking. I tore my dash half apart and drove around like that for a couple weeks to try to find the source but never did. I haven’t noticed it smoking for awhile so I’m not sure if it was the headlights or heater but I keep a fire extinguisher in the truck now.


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On 10/25/2017 at 7:25 AM, cruiser54 said:

I once had rodents packing stuff on the blower motor resistor.....

 

Only once? I should be buying those resistor packs by the case.

 

And, yes -- when the little rascals build their nest in there, it does create smoke and a burning smell. For awhile -- then the thermal fuse pops, and you have a single-speed fan -- it's either off, or high speed, nothing in between.

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  • 11 months later...
I had a similar thing happen in my 91. I first noticed it once daylight savings hit and thought it was my headlights smoking. I tore my dash half apart and drove around like that for a couple weeks to try to find the source but never did. I haven’t noticed it smoking for awhile so I’m not sure if it was the headlights or heater but I keep a fire extinguisher in the truck now.


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Update: Seems as though it was my “headlights”. The switch that controls them was burnt up and melted inside and my headlights eventually stopped working. DIY writeup here- https://comancheclub.com/topic/57308-headlights-not-working-solution/


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