Weird Stuff From Vents

[mhoffman]

OK, this sounds weird but it is perplexing. If I turn the a/c blower in my 88 on after leaving the car parked for a week or more I get a significant dusting from an ash-like powder coming out of the vents. The first time it happened I wrote it up to dust from the garage or wherever it had been parked before I bought it, I ran the vent fan and a/c blower on high (all the dust stopped after 2 or 3 seconds) vacuumed out both the vent intake and discharge and thought it was taken care of.

I took the car out this past weekend after leaving it covered in the garage for a week or so, turned the a/c on and got another cloud. The stuff coming out looks like ash and I can't think of what it may be without tearing the system apart. The stuff coming out is very light gray or white, pretty uniform in size, dust-like flakes- no grains or anything, and quits after a couple of seconds.

Any ideas?

[mtbguy]

Hoses decomposing? Mine looked like a dusty dinosaur dig and were totally falling apart when I worked on the evaporator.

Just a thought!

[tonythetarga]

Is there a smell associated with it? If there is it could be mold that grows from turning off the ac and allowing the cold pipes to form condensation. Mold is everywhere and will take advantage of the right circumstances, ie: moisture, darkness and no air movement. Covering the car further stagnates any natural air flow making a better environment for growing mold.
If that is the case, the solution is to turn off the ac a couple minutes before shutting off the car and keep the blower going which will gradually warm the pipes and discourage any condensation, keeping away the most important ingredient for mold growth.

[mhoffman]

Tony-
no smell and the "flakes" are too uniform for mold.
Could be hose decomposition, but that it only occurs when I first turn the fan on and then only after it has been parked a while is odd. I could see perhaps that dirt/dust from the parking garage, but this looks like fine ash, and the car had been covered...

[tonythetarga]

Fair enough. I have seen a gray color foam 'gasket' at the hose joints and when I touched mine it kind of crumbled, so it could be that stuff.

[aj88cab]

You could take out your passenger floor board, and remove the thermal switch and plastic trim to the evaporator box. With a flashlight you might be able to see if there is something in the evaporator box causing the problem.

Good Luck
Andrew

[Rich Lambert]

Rodents? I turned on the heater in the '66 the other day to see if it worked and a bunch of bird seed husks flew out of the defroster and floor vents. When I got the heat exchangers I emptied a bunch bird seed out of one of them.

[2ndTARGA]

My car is earlier and has the "add-on" factory air, but inside the molded plenum that feeds the A/C outlet grilles, the factory glued in a thin layer of foam insulation. Whether for condensation control or other purpose I don't know, but I found that mine had come unglued and the foam had turned to dust - (like a mini-version of the engine sound pad episode) This stuff would blow out of the vents like ash.

Had to disassemble and replace with new foam material. Could be the same deal?

Ron

[RWebb]

this reminds of a post where the stuff turned out to be foam particles - after 30 yrs it falls apart.

[MarkM911]

Here's a link to the post which describes replacing the foam seals on the butterfly valves in the fresh air box...I'm having the same issue and have this on my to do list.

Cheers!
Mark

Constant Fresh Air

[mhoffman]

thanks all-
I'll try to run it down this evening or perhaps this weekend. It is just odd that it only does it after it has been sitting a while and then only for the firt few seconds of operation.
Plus the material coming out is not a particulate per se, but flaked dust- if you rub it between your fingers it disappears.
I'll start with the passenger's floorboard and go from there.

I'll see if I cannot reproduce it again and maybe get some photos, and I'll close the loop here when I figure out what it is.

Matt