OK, that's not really a guide, but rather sharing some tips following my replacement of driver's side door latch. Sorry, not videos or pics ;-) There are no F10 specific videos on YouTube but the "technology" hasn't changed that much, so there are at least several for other models which should help you. Do watch videos if first time doing this, otherwise little of the below will make much sense.
Note: Left is left and right is right from the perspective of my case concerning driver side door – switch if working on the other side of the car.
Problem symptoms: Door sporadically/permanently failing to unlock from the inside or outside - locking pin raising, but then going back down - door stays locked. Locking pin becoming sluggish on locking/unlocking. Locking pin half engaging, but door still can be opened.
Causes: Door latch (actuator) failure. Usually the plastic gear inside eventually fails.
My case: Though I've been having this issue for a while, since I could still unlock the door electrically (via the button) and it only happened like 50% of the time, I ignored it. But it's a safety hazard and secondly, if the latch completely fails good luck getting the trim open without cutting through the door...
Complexity: It's not a complicated job, but it's a messy one and some care is required. 1 hour minimum, expect some finger damage and sore muscles afterwards.
Prepare:
New latch
Plastic pry tools
T30 bit
Small metal pry tool (optional)
4mm butyl rope (optional)
Hairdryer (optional) – heat gun may be too hot
1. First things first. Locate the correct P/N of the latch you need for your vehicle. That's actually easier said than done. The part number depends on a) The door (front or rear) b) LHD or RHD c) Options (e.g. soft close doors is a completely different part) d) Probably year of production. Enter
http://etkbmw.com/. Make sure you VIN decode if unsure about your options. You can find these latches under Section 51 -> 51_7830 (front) / 51_7831 (rear). Put in your options to filter the list and expect to still be left with a few possibilities ;-) Mine (driver's) side was 51 21 7 202 143. If still unsure I'd recommend you remove door panel and check the three digits printed on your current actuator (they're visible without removing it).
2. Remove door trim - Note: I always disconnect battery, but that's probably me being paranoid.
Remove the decorative top panel trim. Find a good place to grab on the bottom and carefully but firmly pull upwards, then wiggle around to disengage all the clips (also back and forth). Then remove the plastic door recess where the door handle is - that one can be a bit of a PITA. Make sure you only use plastic tools! In my case I'd pull inwards from the left side - this one comes out easily, then you have to insert a plastic tool on the right upper corner section (there's a lighting strip so make sure it's in the corner area or you’ll break it) and press downwards. Also grab the lower right corner and wiggle around until it disengages. These two steps have exposed two T30 screws, unscrew and put aside (I'm still looking for one of mine...). These are all the hard fixtures holding the door trim panel in place. The rest of the door is held into place by several plastic clips. Either use a plastic tool or your bare hands (my case), and pull towards you - I always start in the middle left section, but if you're using a tool the lower left corner may be a good spot. Just make sure you hold the panel at the same time so that you don't rip it off - this could break the plastic locking pin holder on the latch or wiring. Once all the clips are free, push the panel upwards - disengage the corner where the tweeter is and then carefully free the locking pin. Panel is free now, but not quite as it's held to the door by a wiring harness and the internal bowden cable from the handle to the latch, so take care.
2. Door connections
Now remove the white plastic holder which connects the inner bowden cable to the door handle. This one is pretty easy and obvious - just pop off, disconnect the other side from the latch and put aside. As to the wiring hardness you have to decide what to do - it's a pain to remove all plastic clips (still don't know how to unclip them without breaking them) and connectors so I'd recommend just rotating the door panel in a comfortable position and put aside (but exercise care that it doesn't fall and pull on the wiring harness) – my life for a quick release…
3. Sound insulation
This is where it gets messy. You have to peel back about half the sound insulation (the part closer to the latch obviously). It's held into place by butyl adhesive which is some sticky stuff. Do your best, preferably without damage to the sound insulation - take it easy and small sections at a time. Best to tape/clip it so that it doesn't get in the way.
4. Disconnect the door latch
Outside: First, unclip the electrical connector from the latch itself - just press on both sides and pull out. Remove the locking pin from the small round white connector.
Inside: Here you need some good lighting - flashlight or something. Follow the bigger bundle of wires - they're clipped to the door frame and the latch (on the inside), I think in about 3 places with these awful plastic expanding clips. Pull these out - at an angle works best, but you may still damage them. Then comes the internal bowden cable (this one connects to the external door handle). It's about the same design as the internal one, but can be a pain to remove - use a pry tool or brute force. (Almost) finally, it's time to remove the three bolts holding the latch into place - two are on the side of the door and one is internal. T30 again I think. Don't worry the latch won't fall, but even if it does it's not a problem. Now, finally, if it's the driver's side door there's metal pin which goes from the manual keylock to the white plastic opening on the latch. To remove this one lower the latch a bit so that the pin is at about 45 degree angle and pull out - you'll have to do this by feel. And now really finally, wiggle the old latch out of the door - it's perfectly doable but you may have to rotate etc.
5. I recommend you take a break here.
6. Installing the new latch
Insert the new latch in the door and move to correct position. If driver's side you have to insert the metal pin in the round plastic hole blind - just make sure it's properly inserted. You can now secure the latch with the 3 bolts you've previously removed, but don't overtighten them (really). Install the internal bowden cable - should be rather obvious, though again you won't be able to see - visually verify afterwards. Clip the 3 or so plastic clips on the main wiring bundle to the clipping points - two of them are on the latch itself I think. Just make sure no wiring has a chance to get in the way of the internal bowden cable.
Here I'd stop to verify proper operation. Make sure that the latch can lock and unlock. To lock use your finger to rotate the rotary striker (I think it's called) one time clockwise, now pull down on the plastic latch finger where the locking pin inserts. This simulates a locked position. You should be able to fully unlock a) using the external handle b) using metal connector for the internal bowden cable c) using your physical key (from the FOB). All good? OK. If not fix the problem first or risk being locked out later on.
7. Installing sound insulation
OK, BMW say to apply 4 mm butyl rope on the edges (they sell it on Amazon) and then heat with an air blower (hairdryer), but I had enough material left to just re-use. Press around firmly - just make sure the insulation is more or less well glued... ugly stuff.
8. Reconnecting
Almost done now. Re-insert the electrical connector to the latch. Connect the locking pin - insert in the small round hole – make sure to push firmly to engage into place. If you have disconnected any connectors on the main wiring harness reconnect.
9. Re-install the door panel
Take care that the main wiring harness doesn’t press on the internal Bowden cable and that the latter has enough wiggle room. Then check that all the trim plastic washers and clips are still attached – they tend to get around. Start with the upper right corner (under the tweeter), then align along the upper ledge and finally lead the locking pin through the hole. Make sure that the top is well aligned (sometimes it’s tricky) and press down. Then the press around and make sure that all clips have engaged.
Again, stop to verify proper operation. Make sure that the latch can lock and unlock. To lock use your finger to rotate the rotary striker one time clockwise, now you can lock the door with the locking pin. You should be able to fully unlock a) using the external handle b) using the internal handle c) using your physical key (from the FOB). All good? OK. If not fix the problem first or risk being locked.
Also, you now want to check whether the door closes normally. BMW have a special tool for tensioning the lock (about 200 bucks), but I think it ultimately comes down to how much you have tightened the three bolts securing the latch. So, you may need to lighten/tighten them until you get it right.
That should be all.
Sorry, for soft close doors there’s an extra step required, but I don’t have that option. Instead I’m also offering you the ISTA documents for all the good they are…
Again, it’s not a complicated job, but is exhausting – hate working on doors. Not sure how much money I saved on labour, for me it was rather a learning exercise.