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Discussion Starter #1
So today while I was driving I started to hear a "click click click" on the underside of the dashboard..

Doing a quick diagnosis I found out that the noise was prominent between 72-78*F A/C setting if I went lower or higher the noise would stop. So everything pointed out at the Air Mix Motor which is something I am familiar with from my TL-S.


So I decided to do some research a found another thread with a video about fixing it and just went with it. The problem is there is no specific DIY about changing this on the 2G MDX. So here is the Written DIY with some pics:

Tools needed:
1x Philips screwdriver
1x Flat screwdriver
1x 10mm socket and ratchet
Grease (White lithium recommended)
Dialectic grease (Like the one used in the spark plugs)

1.- Remove the lower dashboard plastic cover (The one with the courtesy light) there is a plastic lock you have to twist and then everything just pops out, No hardware at all.

2.- The Air Mix Motor is just besides the Gas Pedal, You cant miss it because of the Neon Green connector it has.

3.- In order to remove the motor there is a small box with a connector I sincerely do not know what is for but its held on to a bracket attached to the frame by a 10mm bolt, Just undo the bolt and put the bracket and black box aside so you can work on the back screw holding the mix motor in place.

X* Optional: In front of the mix motor there is the foot ac vent which kinda gets in the way. You can undo the single philips screw holding it but I could not remove it just wiggle it so I could see one of the screws holding the mix motor.

4.- Before removing the mix motor put the AC to MAX COLD so the mix motor cycles to the top cold position.

5.- There are just 3 screws holding the mix motor 2x on top and 1x on the far back even though the mix motor has 4 holes only 3 are used.

6.- Once the mix motor is out use a pen or something to draw the shape of the "L" arm to the back motor plastic plate for reference so you know which position was in before you start to dissasemble it.

Now that you have the mix motor out. Lets talk about was wrong.

The motor itself is clicking due to the worm drive of the motor. The motor shaft is not keyed so DENSO used a fit pressed key in the shaft that slots to the worm drive. With time this key starts to "move" downwards which makes the worm drive skip and that is the "click click click" we hear. The solution is scary easy.. Just push the key up again to remove all slack in the worm drive. An easy tell-tale is that if you try to turn the "L" arm on the motor you will hear something moving inside. That is the worm drive slack if you fix the slack you should hear nothing if you try to turn the "L" arm.

The mix motor is closed with plastic tabs (same old story) those tabs are incredibly brittle and will break with little effort. DO NOT WORRY! Both ends of the mix motor covers are held together by the screws that hold the mix motor in place so those screws will held the entire thing assembled. So you can take your time and try not to break then or you can just be like me and do not mind them (been there, done that).

Now this part is done with the motor in place!! Dont try to take it out of the mix motor assembly. Dont lift the worm drive either!!

To push the key on the motor shaft you need a flat screwdriver it takes little effort to push it against the worm drive using the motor can to support the screwdriver and leverage. Do so until there is no slack between the key and the worm drive. The worm drive sits in a plastic slot at the end that acts like a support.


Once done grease the gears with white lithium grease as odds are the gears are bone dry.

The back of the bigger gear that holds the "L" arm has the circuit wheel which could use a re-grease with dialectic grease:


Once done re-assemble the mix motor!
Now you can re-install it, There is no special way to do so. Just remember to regrease the levers on the AC Box as they are also bone dry! Clean any dirt or lint that is stuck to them. Use plenty of grease on the tracks. The 2 pins on the "L" arm must be regreased too.

If you did right congratulations! You have no more "click click click" noise and the whole system must be running dead silent.

Hope this helps anyone out! Buying this mix motor new is pretty expensive and if you have everything it can be fixed for Free!
 

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Nice! Thanks! This will be very useful later for sure. (I don't have this problem yet.)
 

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Discussion Starter #3
Thank You! I will try to add more pictures later on.. I did this very late in the afternoon and I wanted to finish it quickly so I didn't have time to take more detailed pictures.

In any case removing the mix motor is not hard at all.. The mode motor does look like a challenge, I greased the tracks of it today including the recirculation motor behind the glove box and it did quiet down its mechanic noise specially the recirculation motor tracks.
 

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Discussion Starter #4
Some complementary pics:

Here you can see the green connector, notice the greased tracks and that lonely philips screw that is one of the 3 holding the mix motor in place.


In order to remove the mix motor you have to remove the lower dash cover which has a little plastic lock that you turn in order to release the cover. After you turn it you just have to pop it out, there are 2 connectors, 1 for the blue LED and 1 for the courtesy light.
 

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2007-2013 Acura MDX AIR MIX MOTOR Replacement
This is another great 2nd gen. Acura MDX maintenance/replacement item, esp. if that incessant clicking noise happens to bother you- not on the top of my priority list, but eventually...seems like for some people, even after having had the air mix motor replaced, the noise eventually returns....:surprise:

That's why this CLEANING suggestion (with detailed steps, analysis) is very VALUABLE! :29:

I might try this myself...looks scary, but if I take to the stealership, surely they will say 'replace the air mix motor!'

 

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It's not so much the clicking noise that is the problem. The air movement is not distributed appropriately so the driver's side can be hot despite the A/C being set to cold. A major sign that something is wrong is that no matter how much you adjust the A/C the air still blows hot on one side. We had this problem in our X so I took the motor apart, cleaned it and lubed it. The A/C on the driver's side was so much better after this.
 

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It's not so much the clicking noise that is the problem. The air movement is not distributed appropriately so the driver's side can be hot despite the A/C being set to cold. A major sign that something is wrong is that no matter how much you adjust the A/C the air still blows hot on one side. We had this problem in our X so I took the motor apart, cleaned it and lubed it. The A/C on the driver's side was so much better after this.
Thanks- this sounds exactly like what I'm experiencing right now- lately it seems like the driver side area in my '09 MDX is heating up even though I lower the temp of the AC into the 60's!

I just need to find some time (and guts!) to tackle this particular cleaning DIY- I do know that the stealership had replaced my Air Mix Motor about 2-3 years ago (forgot why), but it's only been lately that the clicking noise has increased (now accompanied by the slight heat build up inside within the drivers seat area). going to Amazon now to buy some Lithium Grease! :nerd:


 

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The cleaning and lube worked for me. I did the work this summer and it's been good since. Sure beats paying whatever it was for a new unit.
 

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A few additional tips

I performed this same fix on my 2009 MDX driver's side air mix motor assembly today. The advice in this thread is spot on.

Here are a few additional tips:
1. Using a handheld mirror and a flashlight will make it easier to see the motor assembly and the three screws.
2. Tape a piece of paper to cover the open gap below the assembly so that the screws don't accidentally fall behind the carpet/trim where you can't reach them.
3. When prying the motor assembly apart, you can prevent breaking the clips if you go very gently and only pry each clip just a little, one at a time. Pry the clip slightly and at the same time slide a thin blade or knife edge into the case gap that runs around the perimeter of the motor case. Work your way around the case slowly, gently prying each clip very slightly while expanding the case gap with the knife edge.
5. If you do break the clips, hold the case together with a thin rubber band to make it easier to put back.
6. Some of the gears can be freely lifted out of the case. Remove these to make it easier to apply lithium grease to all the gears, and to make it so you can turn the worm gear freely to get lithium grease all over it.
7. When reinstalling the motor, I found it easiest to seat the pins into the two air mix levers (black and white) if I ran the motor to the full hot position.
8. Tape the screws onto the end of the screwdriver with painter's tape, masking tape, etc. to hold each screw while you guide it into the holes.
 

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Great write up! I was looking for this exact thing about a year ago and had to go at it without much guidance but did exactly the same process and it really wasn't that bad. I did take the front seat out which was well worth the extra effort (I'm a big guy!). I did the cleaning/grease repair and it worked for a little less than a year, but same noise started up again, so this time I bought a new one - $80 for OEM including shipping. Unfortunately, I think the rear one is starting to make the same noise....
 

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Discussion Starter #11
Thanks and congrats on fixing it!
I think my rear Mix Motors needs a lube because at 75°F it throws hot air instead of cool air like the fronts.
 

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My AC works just fine. But my heater won't blow hot air until I turn the temp. to above 78F. If outside is 56F, and I set the temperature to 70F, the heater does not work at all. Any chance lubing the air mix motor can solve this problem? I hear no clicking sound for now.

Also I do not have lithium grease in my garage. But I have plenty of silicon paste (the stuff used for brake components and slide pins), can I use silicon paste for lubing? Thanks.
 

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Discussion Starter #13
That temperature is correct.. The system is designed to start heating up north of 75°F.. Supposedly at 75°F its trying to keep the inside "cool" not cold or hot.
In fact from 72-76 is not trying to neither cool or warm the air.. 70s is basically the neutral setting of the A/C Range... If you want hot air keep it near 80°F.
 

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I don't get it. If the inside of the car is 52F after sitting overnight and I set temperature to 70F, why shouldn't the AC system blow hot air? That 70F means I want the cabin temperature to be 70F, not I want the air flowing out of the vent at 70F.
 

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Discussion Starter #15
Its all about the nominal setting for the A/C... You live in a colder place right? well sadly the system isn´t tuned for every single place the people that buy the car need.
For the A/C System 70s is the NEUTRAL RANGE... So in order to reach those 70s it will wait until the Anti-freeze gets to temperature and in your case "heat up" passively the air so it comes out of the vent at 70s.. When the system reaches that temp range it goes into closed loop meaning its now in the "Neutral Range".. Although you might feel it like its getting colder because the system will take its sweet as time to determine its getting colder and it has to open loop again to get the air back to 70s..

If you don´t want the system to behave like this you have to take it to either side of the neutral range, Be it COLD or HOT... Almost all of 70s is Neutral Range and the system will "Try" to maintain 70s but not actively just passively... After you play with the A/C long enough you will learn this quirk and avoid it by simply putting it at 78-79°F. Anything near 80°F will keep the air blowing HOT as the Air Mix is opening the heater core air pass.

And AGAIN the system is INDEED setting the temperature to 70s, What you feel when it reaches the closed loop is the air stopping to be heated because it has reached 70s and the cold windows starting to be felt.
This is not a fault in the system is just only you wanting hotter air than 70s.
 

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Discussion Starter #16
A very simple way to describe is this..


From LOW to 72°F the Cold Air side of the Mix Motor opens up.
From MAX to 77°F the Hot Air side of the Mis Motor opens up.

From 73°F to 76°F is the Neutral Range, both Sides remain shut. UNLESS
The outside temp is colder than the setting which means it will open up the hot side until it reaches the desired temp between those ranges.
Once it reaches it goes back to Closed Loop waiting until you decide to go for any of the COLD or HOT side of the Air Mix Motor Settings.
Until then the temp is slowly starting to decrease because the system is in closed loop (Hot side is shut). Once the air gets COLD enough it will kick back to Open Loop and repeat.

So if you want HOT AIR do not set it in any setting of the Neutral Range.
 

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So I found this thread, it accurately describes my issue. When set on max AC (LOW) warm air on driver side, cold air passenger and rear. When set on max heat (HIGH) hot air everywhere. It doesn't matter if I'm driving or sitting still. Same thing.

I removed the Air mix motor and it was seized. Cleaned and lubed it per these instructions and now it appears to be working just fine, moving the two dampers back and forth.

Any other idea what it could be? Is there another motor/damper that would only affect the driver side??
 

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(stupid question ALERT!)

Is the 'Air Mix Motor' the same thing as an Air Flap Actuator Dorman?

<img src="https://farm2.staticflickr.com/1799/42975845002_ebc9acf69b_b.jpg">

<img src="https://farm2.staticflickr.com/1770/42975844942_da58099dfd_b.jpg">
 

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I also found this, which is likely the correct part (Air Mix Motor for 2nd gen. Acura MDX's):

<img src="https://farm2.staticflickr.com/1809/29157890818_e0a8602f0c_b.jpg">

Long story short, seeing that I lack the tools/mechanical prowess that many of you garage mechanics are fortunate enough to have developed (to allow you take out the existing Air Mix Motor and clean as recommended by this useful thread), I plan on having my independent mechanic replace it with a brand new one (he's not charging for labor- I'm just supplying the brand new part) :29:
 

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For that small difference in price, get the Acura part. Dorman is usually junk.
 
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