Diagnosing Broken Door Lock

[mtndude]

My 1978 driver's side door lock has gotten progressively worse over the past months. It started out taking 2-3 turns of the key to pop the lock up when it was cold outside (I thought this might be normal or at least not a huge problem) but now it's almost impossible to unlock the door, in any condition. It feels like the key is making the turn but somewhere in all the linkage the force is getting lost before it reaches the lock. It's kind of spongy.

If the door is open, pushing/pulling the black lock manually with my hand, it pops up and down beautifully. So it must be something with the actual key mechanism. And also, LOCKING the door with the key works every time. The problem is only in UNLOCKING it from the outside.

Any ideas? Not too excited about buying a new lock for $100+ then having to get the keys re-matched.

[leftover z]

I had the exact same problem with my '77 (the 77 & 78's have the same lock setup). There is no linkage or rods. Remove the lock. There is a "cam lobe" on the end of it, with a lever that is clipped on. With my lock, the "cam lobe" wore down on one side of that lever. It worked fine turning one way, to lock. It would not "catch" to unlock. You just need to replace that lever. I bought a used lock with a good lever for a couple bucks. That way you don't have to re-key a replacement lock.

Hope that makes sense. I have an extra PASSENGER side lever that is on my bench. I can take a pic of it if you haven't taken your lock out yet.

[mtndude]

Thanks so much for the info. I will try that. A pic would be great if you have time.

[leftover z]

First pic is of the lock assembly with the lever attached.

Second pic is with the lever detached.

The third pic is blurry, but in the center of the hole is a tab. That tab gets worn down to the point it won't catch on the locking cylinder when the key is turned. You probably just need another lever.

BTW, the lock cylinders on the drivers & passenger door are identical. It is the lever that is different for each side.

[geoyam]

Try using this as a fix for the worn cam. It was not necessary for me to swap door lock cylinders. The shim seated the lever arm up against the un-worn portion of the cam. The worn out portion seems to be at the end of the cam due to the excess play in the lever arm.

Edited February 20, 2010 by geoyam

[leftover z]

Geoyam, I tried using a shim (washer), but in my case, it wasn't the cylinder that was worn, it was the little tab on the lever arm itself. I replaced the arm, and the lock works as new. Nice pics & details though.

[Reverend]

Where i can get those spring clips? I got 3 locks with no clips to attach. DIY tips also help

[leftover z]

Not sure if you are referring the the little hairpin clips that keep the lever on the back of the lock, or the bigger clip that keeps the lock in the door. You can get both at a junkyard, a Nissan dealer, or most good auto parts supply stores. The clips are nothing fancy or unique to the Z's.

[mlc240z]

Try Ace hardware, I got a replacement there.

[TomoHawk]

My locks had E-clips on them.

[Bruce Palmer]

To build up that worn corner a wire welder works well. Just zap a spot to build it up and file to profile.

[TomoHawk]

Silver solder won't work? It's fairly hard. I was thinking of filling the entire thing and filing out the center to the right shape. Maybe you could just solder up the one corner.