I have a 2004 Acura MDX. When I have the A/C or Heater on, I hear the rattling sound from center dash, Glove compartment area that was really annoying. The sound goes away once I turn the A/C or Heater off. Also, my A/C didn't feel so cold or heater didn't feel so hot regardless of the temperature setting.
So I decided to trouble shoot by listening for the sounds along with some research on the internet. I found the problem to be heater air mix motor. This unit moves the flaps back and forth to control the flaps in the vent for cold and hot air.
So as usual, as the part looks like it's easy to replace, so I went to OEMacuraparts.com to see what this part is and how much it costs which was identified to be 79160-S0X-A01 MOTOR ASSY., AIR MIX $278.98 list price
. Even with Tim's discount, it's still over $200 for this stupid small plasticky thingy so I was determined to find another option. I thought of getting a part from the junkyard/ebay but I figured it's likely to have a same issue.
Then I came across this posted by 1947froggy on youtube.
The part was exactly the same as the Lexus and at the end, I believe this solved my problem. Here's some step by step guide for my 2004 MDX which saved me at least $200 in parts alone (sorry Tim!).
As usual disclaimer, I take no responsibility if you decide to use this information. Working on cars always has inherent risk and it's easy to hurt yourself or damage the car. You're using this information at your own risk.
Before I started anything, I turned on the car and the A/C and set the temperature to the lowest setting (60F). Then I turned off the A/C and the car. I did this so that if I screw up the swivel position (you'll see what I mean below), I have a reference point.
I took the passenger side center console panel off.
If you then crouch down and look towards the center consol, you'll see the air mix motor.
Unplug the green connector and then take the rod off from the white swivel with black hinge. This was bit tricky but I used a small screw driver between the black hinge and the rod to pop it off. The picture shows after I manage to take the rod off.
Remove the passenger floor light which is held by one 10mm bolt. Don't forget to disconnect the white connector (looks grey in this picture).
Remove the 3 bronze screws from the air mix motor and it will come right off.
Now this is a good time to mark the position since this swivel is indexed. I marked at the arrow position along with other areas using silver sharpie for good measure.
Now time for disassembly of the air mix motor. There are several tabs that are holding the covers together. This tab is very delicate so you should use your screwdriver gently and only bend until it clears. I used folded paper as a wedge to work this through and managed to not to break any.
The inside look like this. This is now a good time to mark the top part of the motor, just in case the motor is sensitive to polarity (I don't think it is but just in case).
Now the problem is the worm screw that you see on the picture and the youtube link which specifically explain this issue. I've also read somewhere that the big wheel contacts can also cause problem so I decided to take the big wheel off. Again, before taking the big wheel off, mark the position with your extensively used Sharpie.
The big wheel is secured by the white swivel on the back side with a tab. Now this tab is also very sensitive and it can break. I think I may have created a hairline crack in the process but managed not to break it all the way. Reinforced the tab with superglue and it seems to be fine.
Big wheel is off.
I cleaned the back side of the wheel and contact points with Q-tips and rags very gently. I then regreased them with dielectric grease. I happened to have SuperLube from my suspension work so I used it.
I then reassembled the big wheel and tackled the worm gear. I did exactly as the youtube described accept I ended up using the screw driver to nudge the compression fitting instead of the hammer, plier, and vise. I also made sure there's enough grease at the end of the worm gear and that the it rotates freely while still being snug so that there's no movement. I also cleaned up some of the other gears and regreased them with SuperLube.
I then check all the positions of the parts (motor, big gear, and the white swivel), made sure everything is aligned, and then snapped the covers back together.
I know some suggests to connect the motor to test but since I didn't want to mess with the positions, I just installed it and tested it before I put the floor light and the console side panel back on.
What I also did, which may not be necessary, is to lightly greased the white swivel at the center panel pictured here and also greased the metal rod.
When installing, make sure the metal rod sticking out of the swivel is aligned/connected to the swivel on the center console.
I also found it easier to screw at least one on the air mix motor before you connect the long rod to the black swivel.
Then complete all the screws and connect the green connector.
Then turn your A/C on and change the temperatures.
If all is good, you'll see the motor moving the swivels without making any significant noise.
If all is good, install the floor light with the 10mm bolt, connect the wire to the floor light, and then reinstall the center consol panel.
Since I did this today, it may be early to tell but the sound I can hear regularly when set at 70F to 72F is completely gone.
Now I have extra $200+ to spend on something else