Solved: musty smell in climate control. The leaf retains water in the air intake!

This was a surprise. My child is very sensitive to smells, and always complained about the leaf with climate control on at all (I had to insist when it came to defrost!).

I've found it, fixed it.

The Leaf's fresh air comes in via an air plenum just below the windshield. Water from the windshield drains into this rather large plenum, and drains out either side. There's a black plastic access hatch on either side and the middle.

Inside center I found a layer of black scuzz. But most surprisingly, I found the space drains side to side, but has a dip in the middle that retains water. The dip is right where air is sucked in by the fan system. Cleaning it out (and replacing the cabin air filter) did the trick. For cabin filter instructions see http://sfbayleafs.org/technical/diys/leaf-cabin-air-filter-replacement/

I just washed the area out with a hose, but could not get it to dry on it's own. Even driving the car uphill, downhill, and parking on a slide slope was not enough. I finally had to get a rag in there (which was a pain) to get it dry. If it's retaining water, then no wonder it's letting things get musty inside.

Thank you for this post! One of my daughters is very sensitive to the smells which come from our LEAF's HVAC, so now I have an idea how to address it.

Can you carve a piece of smooth plastic foam into a flattened pyramid shape and glue it into the dip?

brycenesbitt said:

...Inside center I found a layer of black scuzz. But most surprisingly, I found the space drains side to side, but has a dip in the middle that retains water. The dip is right where air is sucked in by the fan system. Cleaning it out (and replacing the cabin air filter) did the trick.

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Thanks for this info.
My cabin filter has been replaced twice and probably needs it again.
Have noticed long time in LEAF does cause me some coughing.

I was considering having dealer do the disinfectant fumigation on the HVAC, something I have had to do on prior vehicles that developed sweet smelling mustiness.

But I'll disinfect and clean the water accumulation area first.

Have noticed long time in LEAF does cause me some coughing.

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It could also be the recycled plastic seat material. That stuff stinks of rubber for years. Why couldn't they have used recycled soda bottles...?

I clean and replace my filter every 6 months and everyone else should too. Waiting a year is ridiculous. Another thing you should do is run unconditioned air thru the system for at least 2 mins before EACH shutdown the system was used.

Finally, I turn on the system on hi fan, I always have windows open for first minute or two to ventilate and help move hot air out...

Please note: I did NOT find water in the dip under the hood: I found precipitate. Meaning, the black slime that indicates water pooled there in the past. The area is very hard to clean, because there's a body color metal baffle that prevents easy access with a hand.

Question "Can you carve a piece of smooth plastic foam into a flattened pyramid shape and glue it into the dip?". Answer: no, probably not, you'd need to glue it to keep it from retaining water, and the glue would probably be worse than the water.

I clean and replace my filter every 6 months and everyone else should too. Waiting a year is ridiculous.

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That's hyperbole. You must live in a wet climate, because I'm on my second cabin filter since the car was new, with this one in place about 20 months, and it's only now starting to smell a little musty. The first one was changed after a year, and was about 1/4 dirty. BTW, I'm also very sensitive to odors - I doubt anyone else would smell the current filter. Since I'm hoping to get a Bolt in 2-4 months, I doubt I'll have it replaced.

Cyan o-acrylate (my spellchecker insists) glue, BTW, dissipates very fast.

I have a similar annoyance with my 2011 SL. When switching from recirculate air to outside air I get a blast of air that smells like hot stagnant water. The smell goes away after about 30 seconds. Air filter is new, and properly installed. I am waiting until winter to completely take apart and inspect the HVAC system.

Also whenever I turn off the AC, the system insists on switching to outside air automatically, giving me a tiny whiff of aforementioned stinky air.

Just a followup on this topic: I tried to remove the black grill from the above the plenum where the climate air enters the vehicle. I knew how this was done since I had watched glass repair people replace the windshield. Unfortunately, when they replaced it, the glue was still sticky and the large plastic vent piece is now firmly glued to the windshield. In any case, I can see and access the area mentioned just by removing the small plastic piece in the center (a much easier task!).

In our case, there is currently no standing water and there also is no mildew in that area. I only saw a small amount of dirt left from water.

FWIW, we normally have had no issue with the smells in our LEAF because it is normally garage-kept. But during this spring and early summer, our LEAF spent an extraordinary amount of time parked outside the garage since we had other things stored there. I believe that is when we had the biggest issue with smells.

One thing I will say is that the way the metal is shaped in that area, I would suspect that anyone who parks outside against a curb with the passenger side lower than the drivers side (which is the normal condition if parking against a curb) would experience this issue more than others. If that is your situation, you may wish to find a way to park the car so that the drivers side is lower than the passenger side. In that case, there should be no standing water in the middle area and very little standing on the passenger side.

In any case, thanks again to the OP, since I now know where to look if we start experiencing the smells again.