Date registered: Mar 2017
Vehicle: 2013 ML350
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2013 ML350 AC Odor Smell Solved, DIY, Pictures
My AC had a bad odor at start-up, especially when it was hot outside. I read about various ways to eliminate the smell, so I proceeded to do them all plus a couple not mentioned. I removed the intake cover for the system from under the hood area, replaced the one dust filter and two carbon infused air filters with aftermarket filters, and nothing changed. All work was completed before driving the car for the day.
Then I completed these four steps:
1. Sprayed the evaporator (air blows over to change the temperature of the air in the car) with a foaming cleaner. I did it with two different cleaners.
2. Changed all three filters with new Mercedes filters.
3 Used Mr Clean, hand towels, and elbow grease to thoroughly clean all surfaces air passes over from the vent in the hood all the way to the fan.
4. Used an Ozone generator to kill any type of growth in the system.
The entire process took several hours and I am pretty handy when it comes to repairing things.
Details for each step:
Cleaning the evaporator probably had the greatest affect on the smell and I also did it twice. The first time I only cleaned the evaporator, which eliminated about half the smell. The second time I complete all four steps and the smell is completely gone.
Step 1A - Remove the access panel under the glove box. There are four torx screws you remove, think it's a size 25 torx screwdriver. Four yellow arrows point to the screws.
Step 1B - Lower the front of the panel down, like opening a door. Yellow letter A, lift up the top lip of this joint to unclip the two panels. Blue Arrow - I slid a thin towel between the plastic parts to protect against scratching the plastic.
Red Arrow - this edge is like a hook to keep the back of the panel above the carpet. Note how it is installed so you can put it back the same way.
Three yellow arrows - metal clips required to hold screws in, make sure they are in the same place when you try to close up the area.
You can also remove this panel completely by removing two electrical connections at the end of the red and yellow wires to the right.
Step 1C - look up behind the AC controls, above the carpet, and you should see a black tube next to the electrical wire grouping. Gently disconnect the tube highlighted by the green arrows by pulling it about an inch toward the door. Do not pull this down toward the floor.
Step 1D - Two pictures. This is what you should see. The green arrow points to the orifice you use to inject the cleaner.
Step 1E - I've done this step twice. I used Kool-It (from Amazon) the first time. It's only 6 ounces, and drained out of the drain tube as expected. It's the only time I've seen any A/C related drainage under the car. The second time I used FJC Foaming A/C Evaporator Cleaner with Odor Control (Amazon). It has 16 ounces of cleaner and much more product - and dirt - drained from the system. Use the plastic tube that came with each product and squirt it up into evaporator box to get as much product to cover as much of the evap as possible. I was able to move the application tube around more with the FJC cleaner as there is much more cleaner in the can. I placed a towel on the floorboard before squirting any product into the system just in case. I also did not squirt any of the product through the fan blades, as illustrated on the Kool-it box. I did not use a cleaner to get the foam out, just let it do it's work and drain by itself. Instructions say to let it sit for 15 minutes, then turn on AC to generate some moisture accumulate in the evap box, which I did.
Step 1F - put it all back together in reverse order. Make sure the lip on the back of the access panel gets over and behind the top of the carpet all along the top of the foot well as well as the metal clips previously noted are properly position over the holes. I didn't do anything special to the air ducts attached to the access panel, they slipped back into place.
Step 2 - I bought and installed new filters from Mercedes. They were $90 for all three from my dealer, just a little more than the after market filters. I completed Step 3 and part of step four after removing the filters and before installing them. I also installed the filters through opening under the hood (well documented on this forum).
Step 3 - I removed the plastic housing component covering the dust filter and cleaned everything cleaned everything from the hood vent all the way to the fan with Mr Clean. My particular intake parts had some blue stuff on them, probably some sort of residue from engine stuff. You have to raise the hood up a little higher than normal (it can go almost vertical) so you can reach all the way down the fan. Instead of spraying cleaner and letting it - and the blue stuff - drain into the system, I first dry wiped all surfaces with a cloth, then wet a clean cloth and wiped everything down a couple times and let it air dry. I used several wet cloths as they ended up with the blue stuff on them and I did not want to smear the stuff all over the place. There are a couple of foam pieces sealing plastic parts. Mine parts had the blue stuff on the foam. I sprayed enough cleaner to soaked the foam parts, compressed the foam to get the cleaner deep into the foam, and carefully compressed and wipe the foam as to not damage the foam pieces while getting the blue stuff off, then let the foam dry out without rinsing out the cleaner. I believe the blue stuff had something to do with the odor problem and thoroughly cleaned all I could see. There is also metal (the firewall) in the duct, which I thoroughly cleaned all the parts and joints as well. I cleaned everything between the fan and the hood.
Step 4 - This took a few hours. I ran an Ozone generator in the duct work from outside the car (see the one I bought). First I put it as close to the fan as possible and covered the opening into the engine compartment with a towel, to force the ozone over the evap and into the car. Two cycles took about an hour. I then installed the plastic piece inside the engine (did not install the filters yet) and ran the Ozone generator for another couple of 30 minute cycles, covering the hole inside the engine compartment to force the ozone into the car. Then I turned to car's fan on low, attaching a battery charger while running the fan, and ran two more 30 minute cycles. After a couple of 30 minute cycles, I reinstalled the filters and all the housing parts, then drove the car, cycling between the lowest temperature AC/high temp heat/low temp AC, to clean out the evap box. Be careful and avoid inhaling the Ozone as it may hurt you.
Probably overkill, but there is no longer any bad odor or smell in my car.