Door Unlocking Issue

I’ve read many topics on door lock problems on this forum, but haven’t seen one exactly like mine, at least that I’ve recognized. My issue is with a 1992 XJ6 vanden plas, 75,000 miles. I recently acquired the vehicle and discovered the door locks, trunk, and gas cover will not unlock using the mechanical key in either the driver side or passenger side key switch (there is not a keyless entry system installed). The key will lock all of the locks (plus trunk) when used in either door, but sadly, won’t unlock a thing from the external door locks. The doors and trunk will all unlock when the drivers side or passenger side button is pulled up. They will also all lock when either button is pushed down. The mechanical key will lock and unlock the glove box and the trunk, and works in the ignition switch.

I suspect mechanical linkage to be the culprit, but I find it odd that both door locks would have this same problem at the same time. Before I remove door panels, anyone have any thoughts?

Very possible the door handles are replacements and the locks within them were not changed when the handles were replaced.
If you have a tibbe style key, well, any tibbe key will activate the lock but only a correctly coded key will unlock that same lock. this is why you can lock your car but not unlock it.

There are quite a few posts in the archive by motorcarman on this subject.
It is possible to recode your locks but this will involve removing the door handles and lock barrels.

I’m guessing Larry is spot-on. Here is a service bulletin that descrbes the Tibbe key and lock re-keying process:

76-64 Tibbe Door Lock Repair.pdf (2.7 MB)

Here is a link to a vendor that offers Tibbe keys. No affiliation, I have never purchased from them, I just bookmarked the Web site for future reference.

Thanks Larry. I had thought of that possibilty too, but have the same wonderment as to the likelihood of both handles being in need of replacement over time. In either case, tearing into the door will be needed.

Thanks Mike for the link.

If door handles are out of adjustment, they will break. Very common issue, I’ve replaced passenger and one rear myself.
There is a permanent solution to handle breakage, adding a small nut to the linkage will permanently prevent breakage as it prevents the linkage going out of adjustment.

Solution is in the archive posted by @katar83

Thanks again! Yes, I did read about the nut hack. Great idea! And quite clever.

I will report back out on what I find. It will likely be a while since there are several other repairs currently in the queue. These involve taillight lens replacement, water in the trunk, and slight gas smell in the trunk.

These door handles are made out of potmetal and do break frequently when they are not adjusted properly so it is not uncommon at all for several door handles on a car of this vintage to have been replaced over time.

I have owned my 1994 car since 2007 and I have replaced the door handles a few times before I learned about the trick with the nut.

Thanks Steven. My wondering about the odds of multiple breakages has ceased with yours and Larry’s responses. I’ve resigned myself to again expose car door innards. I’ve been there before, just never with a Jag.

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One trick is if you feel that there is more pressure required to lift the handle put a bit of pressure against the door, this relieves the pressure on the operating system.

If the handle has to raise up beyond it’s (badly!) designed operating range, it will snap. This is where the little nut comes in, it can release the door latch right at the start of the handle travel and keep it there.