Quick background - The 6 CD changer as fitted to many models (in my case PN 65 12 6 913 388 fitted to an E46 facelift saloon) is quite prone to not reading discs. It can start tempermental, but ends up just saying "NO DISC" on the head unit when you try to play CDs.
I have already spent £30 on a 2nd hand unit which didn't last very long, and eBay refurbishment costs about £90. I did a quick google and discovered that it's a common fault with many changers as a result of the disc selection mechanism not working properly, so I thought I would give it a go myself. I seem to have got both changers working again, although I fully disassembled the first one to see how it worked, and damaged the ribbon cable on reassembly, rendering the unit U/S. Full disassembly is not recommended, and not required.
For clarity: when I refer to "left" and "right" I am using the designation on the plastic covers that secure the H/V stabilising springs. Front is the side the CD magazine enters
WARNING: The CD changer has unfinished metal edges inside that are capable of causing injury (as I discovered when I started leaving blood inside the changer) and may render your CD changer inoperable, and will almost certainly void any warranty on the unit. No responisbility can can be accepted by either myself or BFI for any damage caused when following these instructions.
Step 1) Remove the CD changer from the car. This varies depending on model, and for safety you should disconnect the battery first.
Step 2) Remove the cable connection module from the back of the unit. This requires removal of 2 screws (#1 philips), one centre back (pictured) and one at the back on the left hand side of the unit.
The unit then slides to the left hand side of the changer and pulls away.
Remove the ribbon cable by pulling the securing tab in the direction of the cable, which will then fall out.
Set this module to one side.
Step 3) Remove the brackets that secures the changer in the car (#2 philips) and store securely with the screws.
Remove the plastic covers that secure the H/V tension springs.
Remove the remaining 5 screws that secure the top cover. 2 on the left and 3 on the right. (pictured, right rear screw)
Step 4) Remove the top cover. This is quite fiddly. I found the best way is to start by releasing the tabs that join the plastic front and the top cover (gently, I broke one on the first changer). NOTE: The plastic front cover is not removable until the top cover has been removed as it is secured with further tabs internally. Pull the front top away, then spread the bottom edges of the top cover in order to clear the tension spring adjusters. Set to one side.
This concludes the disassembly required, and you should have the following:
In this photo I have reattached the cable connection module in order to test the changer with the cover off.
The large arm that is visible is the mechanism that extends the tray in the magazine, I merely moved this backwards and forwards, then tested the changer in the car, where it functioned.
I admit I haven't really done anything, because I wasn't really sure what to try and clean or grease. If anyone has any tips please contribute them. It did feel stiff and stuck in places.
Reassembly is the reverse of disassembly, the top cover is a bit fiddly, because you seem to need to get all sides in at the same time. The top front edge should be engaged with the plastic front cover if not removed, then engage the back edge into the bottom part of the case, then install the screws. Reinstall the cable connection module. Replace the tension spring covers and mounting brackets.
If you wish to disassemble further, remove the front panel by releasing the 4 tabs on the bottom, and the tabs on each side (that you couldn't get to with the top cover on).
The changer mechanism is held in place by 2 rubber mounts on each side, and the tension springs, simply pop the rubber mounts out, manouver the spring supports out and then undo the screw that secures the PCB supporting the ribbon cable. WARNING: the tension spring is a fiddly little blighter to get back in. I strongly suggest that the mechanism is not removed from the lower part of the case as it is not necessary.
To reinstall the mechanism into the lower case I suggest first connecting the tension spring to the hooks on the mechanism, then securing the adjuster, before reinstalling the rubber mounts. Reassembly then continues as above.
I realise there aren't many pictures, so if you would like any more pictures just let me know what you want pictures of and I'll try to get some.