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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 and 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:
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 beside the Gas Pedal, You can't 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 it is 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 mixing motor in place.
X* Optional: In front of the mixing 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 mixing motor.
4.- Before removing the mixing 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 mixing motor 2x on top and 1x on the far back even though the mixing 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 disassemble it.
Now that you have the mix motor out. Let's talk about what 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 hold the entire thing assembled. So you can take your time and try not to break them 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!! Don't try to take it out of the mix motor assembly. Don't 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 the 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 it 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!
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 and 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 beside the Gas Pedal, You can't 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 it is 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 mixing motor in place.
X* Optional: In front of the mixing 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 mixing motor.
4.- Before removing the mixing 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 mixing motor 2x on top and 1x on the far back even though the mixing 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 disassemble it.
Now that you have the mix motor out. Let's talk about what 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 hold the entire thing assembled. So you can take your time and try not to break them 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!! Don't try to take it out of the mix motor assembly. Don't 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 the 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 it 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!