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Discussion Starter · #1 ·
Hi,

I have a 2002 P38 with only 55k miles on it. I bought it about 4 years ago, and since the day I bought it, the passenger nor the two rear doors will turn the interior light on. The driver's door will occasionally, or if I give it a good smack. Everything else on the car works fine. I checked using a Nanocom that the opening of the doors on the passenger and the two rears aren't seen by the BECM, and that the driver's, the liftgate and bonnet are.

So, my question is, what pushes (or stops pushing) on the microswitch to make them indicate the door is ajar? They are in the latch mechanism, and the activate when the latch is in the open position. I am thinking that whatever is supposed to move (or stop pushing on, would be good to know which) the microswitch just isn't moving far enough (or moving away far enough) to "activate" the microswitch. Likely due to not being used much over the past 20 years. I am tempted to buy a used door latch, and take it apart just to see how they work. I may try operating the latch mechanism with the door open to see if I can manually move it into a more open position and that activates the interior light.

Any insight appreciated. My other P38 (2001) with 182k miles on it all works fine including these door ajar microswitches....

Austin
 

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Inside a RH door latch (RHD so your drivers latch would be the same only mirror image).

Door open

Photograph White Wood Gas Electronic device


Wood Bumper Gas Machine Engineering


Door Closed

White Gas Wood Auto part Machine


Wood Gas Office equipment Machine Engineering


From these you can see that the lever pushes the microswitch in when the door is closed and releases it when open. So your microswitches are sticking through lack of use.

To be perfectly honest, the worst thing you can do to a P38, or any car for that matter, is not use it, things deteriorate with age and don't always do what they should when you ask them to. That's why I would never pay over the odds for a low mileage car, in fact, I'd pay under the going rate as I know I'll be needing to get involved in repairing heater blend motors, door latches, EAS air springs, brake callipers, etc, all things that need exercise to keep them working. Mine does 20-30k miles a year and never gets chance for anything to start to seize up so everything continues to work as it should.
 
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On YouTube the Norwegian fellow has a pretty good video showing how the door latches work but I don't recall if talks about door open/close.
 

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Discussion Starter · #4 ·
Thank you very much for the info. That's exactly the info I was looking for, to know the switch state when the door is closed was pressed or released. I will pull the latches out and see if I can get these switches "unstuck".

This car was very very well kept (in a humidity and temperature controlled garage in California), and these door ajar switches are the only thing that doesn't work. Everything else works as expected. It was used, just not very often.

Are the other door microswitches in the released state when not "activated"? I should go check that the door locks on each door activate the central locking. Never tried that. The central locking works, but I only activate that from the key fob, never tried from the individual doors.

Best Regards,

Austin
 

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You can't operate the central locking from the rear doors, only from the sill locking button on the fronts, the fob and the key slot in the drivers door. If you have a Nanocom, then you can easily check for a change of state on the drivers keyswitch and the CDL switches in both doors.
 

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Discussion Starter · #6 ·
Thanks. I never sit in the rear, much less lock the doors from the rear. Front passenger door lock button works fine, activates central lock. Driver's door key switches seem to be fine as well. I do have a Nonocom. And, as you said, rear door lock buttons don't do anything but lock that rear door.

Do the rear door latches only have one microswitch, for the ajar?

Thanks!

Austin
 

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Discussion Starter · #8 ·
Thanks for the confirmation. And the fronts appear to have three. One for the CDL, one for the key and one for the ajar. And since these door latches are not RHD or LHD, on mine the right still has the key microswitch, but it is unused, since that door handle has no key.
 

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Discussion Starter · #9 ·
Any advice for removing the latches (I have taken the door cards off a few times, and repaired misc things in the doors of my older P38, but never taken a latch out) once the door cards are off, and any advice for taking the latches apart to try to get the switches operating?
 

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Unclip the cable clips so they can be pulled out from inside the door and the electrical connections to the latch can be unplugged. Be aware that as soon as you unplug a front latch, the central locking will engage to lock all the other doors. Undo the clip that holds the handle rod to the latch and disconnect that one, take the screw out that holds the handle to the door, push it forwards and pull it out slightly. This will allow you to carefully unclip the rod attached to the key lever. Unscrew the knob from the top of the sill locking rod and unclip the outer of the internal door release. remove the 3 screws that hold the latch to the door, lower it downwards and twist and you should be able to pull it out the door and release the inner of the internal handle cable. Getting it out can be a fiddle as there is a lump of metal, that serves no useful purpose whatsoever, that catches on things (cutting it off before you put the latch back in is the answer).
 

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Discussion Starter · #11 ·
Thank you for the advise. I'll probably start with the rear ones as they look easier and will get my feet wet so to speak to deal with the front ones.
 

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Rear ones are harder as you have to take the window regulator out to get to them......
 

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Discussion Starter · #13 ·
Doh! That was unexpected... OK, so passenger front it is. Thanks! Any chance you're in the neighborhood? ;-)
 

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Note: the door-open microswitch detects both the half-latched and fully unlatched conditions of the latch itself. It does not detect that the door has opened or closed, so you can easily test by closing the latch with a screwdriver while the door is still open wide for access.
 

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"This will allow you to carefully unclip the rod attached to the key lever"

Be very carefully here as it is possible to break off the lever from the door handle while trying to remove the clip and rod.

Sawing off that arm that sticks out is a good idea. I struggled to get the driver's side back in but the passenger's went in with no problem. Don't know why.
 
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