Door Lock Fault Finding

[CRC]

As there's not a lot to do or places to go at the moment,  the weather forecast was good  and I needed a challenge, I decided to strip down the drivers side door lock on the Boxster and see if I could work out why I was continuously getting intermittent issues with it.

I've owned the car for a couple of years and it's always had the classic "Boxster door issues" - windows wouldn't drop to clear the roof, red light on on the dash button, doors would continuously try and lock when the car was open etc., etc ...... but not always, as sometimes it would be as good as gold, then revert back to it's bad old ways again for no apparent reason.

Early on in my ownership, I changed the drivers door lock for a £25 Ebay cheapo, which kind of worked, but wasn't exactly right, so I gave up with it, cleaned up the old one, out it back in and it worked for a while, but then went back to its old intermittent ways again .......

This week I decided to go to town on it, so took the lock off the car and stripped it down to have a good look. With a bit of thought, it's quite easy to take apart, but the key thing is to separate the electrical module  from the mechanical module - a couple of screws and arms but take some pictures of the springs before you do

The attached pictures show what is inside the electrical module - no chips or anything fancy, just a couple of small motors and some micro switches.

I started checking through the conductivity from pin to pin and (after a few hours) realised that the 12 VDC common from pin 8 of the plug was really dodgy - sometimes perfect and sometimes just not there at all, so I used a solder sucker and soldering iron to get rid of the solder on the joint shown on the Lock4 picture, and then I realised the problem.

There was no  "pin" or "tang" coming up into the circuit board hole from the "claw" beneath, meaning that the solder in the hole must just haven been resting in the arm of the "claw arm" underneath, rather than physically bonded to it ...... a real "touch and go" connection and it must have been made like it at the factory.

After a few more hours fiddling, I managed to get a new pin ( the arm of an old diode) that dropped through the hole, was soldered in place and made a good tight contact on the lower claw, with possibly a solder connection as well, but it's just not possible to get a soldering iron in there to complete the joint perfectly.

It wasn't pretty, but it worked and after more testing, re-assembly and re-installing, the car locking and unlocking now works like it should, and fingers crossed it will stay like it.

 

 

 

[PaulQ]

👍

[½cwt]

Great investigation work. Gives a repair rather than just replace option to solve this fault.  Poor design (from SAGEM? from the name on the circuit board) to rely on just a dab of solder with no wire, explains why it is such a common problem if this solder joint fractures and becomes an intermittent or broken contact.

@Araf, can this be added to the How Tos?

[CRC]

Thanks,

Oh, and one thing I forgot to mention, is that when you're re-fitting the lock, make absolutely certain that you get the door key "arm" to locate in the round cam receiver on the door lock (really fiddly as you have to feel for it without being able to see it).

Luckily,  I remembered to test this, realised it hadn't located at all, and had to loosen  the lock and re-fit it again.

If you get this wrong, in 5 days time when the remote facility has switched itself off to conserve the battery, you'll find that you have a car that it's not possible to unlock the doors on ...... not good at all and I'm not sure how you'd get over that one.

 

 

[pacificjuha]

Very good find CRC and great explanations! I just had the original door lock open yesterday while the replacement is on the door now - need to open the original agian to check same like what you had found 👌