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Door Lock stopped working with the Key

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Hi All,


A bit of help and advice please from those who know what is inside a door lock, and also how to get inside it!!


Problem started this weekend, when I locked Tina up on the passenger door with the key, then couldn't unlock it again! The key would turn in either direction but with no noticeable resistance.

Locking and unlocking the door from the inside worked fine, and in either position the door button operated correctly. It is only the key locking mechanism that did not work.


Today I took the door card off and removed the door handle to see what is what.


This photo is what the door locking mechanism and plunger looks like when the lock is working fine:



And this one when failed



You can just make out that the plunger has worked its way out very slightly from the housing, when this occurs the key will not operate the lock, but will turn.


When the plunger works its way out, it is then possible to wiggle and pull the plunger out of the housing further - to the length that it would be pushed out by the button to operate the door opening pad. Takes a bit of wiggling, but I can then push it back in.

If the plunger is pushed back into the housing, the lock operates normally.


Due to the way that the door lock operates, the linkage that is attached to the small arm on the door handle lock, there is a propensity to apply a force that encourages the plunger to work its way out.


At the moment, to get round this behaviour, I have extended the set screw in the end of the plunger to almost take out the slack/free play between the plunger and the pad it operates on. The result is that when the plunger works its way out, the pad has the effect of pushing it back in and keeping the lock operating.


I now have 4 thou gap between the plunger and the pad. The "Haynes book of Lies" states that it should be 0.0625" (a bit exact that measurement :blink: )



1. Why does my plunger operate like this, has something worn, broken, dislodged?

2. Can I fix it?

3. Why should there be 0.0625" gap between the plunger and the pad? What is wrong with my current 4 thou?





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  • 1 year later...

Subject Bump up for Brian as he is abroad on hols! "limited access"

Anyone got any good info on this subject??

or links to another topic covering it on the forum??

And I can send it to him!

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Just grabbed a bit of hotel internet time..............


I did a temporary fix a year ago, but it's starting to play up again. I'm sure I had a PDF of how to take these apart etc at home, and it didn't end up on my laptop when coming abroad. I've read and re-read my Practical Classics that I brought with me and I'm pining for more car reading. ..... and was looking for a bit of lock reading material while soaking up the sun :-)


Alan - Thanks for being helpful :-)

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Hi Brian,

the locks are quite simple. You need to get inside it to see what is going on.

Write down how you take it apart - with the odd drawing.


There are two screws on the back plate - take them out.

There is a pin in the plunger holding the barrel in place - knock it out.

The whole thing can now fall to pieces in front of you.

There is a double action spring that gives the key a rebound effect take it off.

There is an internal plunger that runs over a lip - the plunger and lip should have square edges - otherwise the plunger slips off the lip - these can be filed square.


That's basically it.



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Just to update.......

I found the PDF at home (back from holidays and a superb sun tan B) ) which expains how to take a barrel apart (didn't need that bit). I just like to know what is the other side of stuff before I take it apart, that's all.


Locking mechanism cleaned up and should now be working reliably. Found a shard of metal about 2mm long in there, my guess is that it was preventing the plunger from properly seating in the "unlocked" position and so easily worked itself out or wouldn't go in the unlocked position in the first place.


It looks like my door handle / locks have been filed down on the top/bottom edges at some point - maybe to smooth their way into the TR6 door skins that she's now wearing and one part was holed very slightly. Might be where the offending item comes from.




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  • 1 year later...

Came across this topic while trying to sort out my recalcitrant locks. I have one working, sort of, but the other has the same problem as Brian, the internal plunger slips out. Below is the better of the 2, now in the drivers door lock. Roger referred to square edges needed - as far as I can make out the article below is not retained at the lock barrel end except by the spring loading. There is no lip as such on either of my barrels to form a positive check on the "pegs" at the end.


The problem with these items also appears to be wear on the other ends of the longitudinal ridges, resulting in no engagement with the locking lever.


Has anybody sourced replacements, or modified a similar part (not adverse to a bit of fettling)?







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Is this the near-side or the off-side you have problems with?


I suppose you have made sure the lock-nut is tight? The plunger gets misplaced it this goes loose.


Probably the plunger is worn. I bought some handles from the USA because they have unworn handles that go on our drivers side. But actually the plungers are not handed.


Finally got your thumbnail to expand. Plunger looks OK.


I think you may have this assembled incorrectly. There is a funny spring that rotates the plunger. You can get it together and they do work sort of with the spring not engaged properly.

Edited by AlanT
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It has been a problem on both sides, the locks setting themselves and not responding every time to the key. I have used the best internal plunger (pictured) for the driver's side, it was on the passenger side. The lock nut is/was tight on both sides.


Can you expand on the spring? I have the long spring and the key centering spring, so I am not clear which would rotate the internal plunger.



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