Trunk Soft Close Upgrade

Article by: Johan

Article applies to: E32 models

Retrofit Description: As promised some pictures and comments about the soft close retrofit I did last weekend.

The parts required for this retrofit are: the soft close lock, the control unit and the wiring loom:

It’s a pretty simple install.

The wiring loom only has three connections: one for the lock, one for the control unit, and one for +12v and ground (ok so actually there are four connections):

Remove the lower, rear and left side carpet in the trunk.
Then – remove the cable guides.

Remove the jack and the rest that’s in the way of the lock.
Remove the central locking motor pin to the lock and the three bolts holding the lock:

Now install the wiring along the path of the other wiring via the back of the trunk, the cable guide and through the rubber grommet between the rear seat and the trunk:

The control unit will end up on the right side in the deeper part of the trunk:

In a perfect world you will have the box especially for the soft close control unit. But this was gone at the scrapyard.

I’ll probably order a new one as the box and the lid only costs 12 euro (about US$15).

– Hook up the +12v and ground to the corresponding plug on the module carrier and a ground collection point. But first CHECK the voltage at the pin.

I had a connector which fit but physically but it only gave 1.5v so that was a no go. I ended up hooking it up directly to the battery with a 15amp fuse in the path.

– Now comes the painful part for me. The lock didn’t fit. Apparently somewhere around 88 or 89 the design of the back was changed.

And mine is an 87 model. So I had to do some cutting with a Dremel:

The bare metal was liberally covered in zinc primer.

The locks side by side:

And what did all this labor get me? A cool self locking feature. I can now gently push the boot down and it’ll pull it into the lock on it’s own. This will probably be the reason I can’t get into my trunk when it breaks. . . but oh how I love these little gadgets.

What’s next? Well park distance control!

If you buy the parts new it will set you back between 400 and 500 US$! It will be much cheaper getting the parts from a scrap yard. Was soft close standard on any models in the US?

I do have the part numbers for you (eBay is your friend here):

And I probably missed some screws to put it all together.