Door locks only when open and on 1st latch
 

I've never been able to lock the driver's door believing the problem to be a poorly installed after market central locking actuator.

Today I removed that and found:
1) Locking works fine when the door is open;
2) Locking works fine when on the first latch;
3) Does not want to lock when on the 2nd latch.

I've oiled everything and everywhere and I've adjusted the pillar catch. No lock luck.

Is there a known issue that could be causing my problem?

Re: Door locks only when open and on 1st latch
 

Since our trucks didn't come with power locks there probably isn't a known issue. That being said the fact that it is the drivers side leads me to surmise that 50 years of wear have introduced play in the mechanism that the passenger side doesn't have. (Which is a known issue) I suggest finding a way to view the mechanism while operating and compare the two sides carefully. Maybe one of them newfangled cellular phones would help. I think you will find too much play on the drivers side mechanism. I also suggest searching "door lock problem " in the search box above to help get an idea what you should be looking to find.
Good luck

Re: Door locks only when open and on 1st latch
 

Latch assembly is worn.... replace. I had the same problem and thought it was the locking assembly mechanics but was told it was a worn latch so I replaced it and problem solved.

I might and you may want to try, I could lock it if I pushed/jarred the door in while turning the key at the same time.

Re: Door locks only when open and on 1st latch
 

Seems like a common issue from what I have seen. You have to put pressure on the door as you turn the key to lock. I adjusted the strike plate on the body side out just a tiny bit and it helped some. Just a little extra push now on the door and it locks fairly easy.

Re: Door locks only when open and on 1st latch
 

Read my door locking problem thread, there is a link to it in my signature line.
You need a new door latch, the repro latches work good.

Re: Door locks only when open and on 1st latch
 

Bingo!! Works for me. Thank you!! I conclude it is the tip of the latch that prevents the rotating toothed gear from rotating in the opening direction that has worn. This results in the toothed gear "resting" in a position that prevents the door lock latch from engaging.

Pressing on the door results in the toothed gear rotating "forward" just a wee little bit, enough to allow the lock latch to engage.

Re: Door locks only when open and on 1st latch
 

I found the toothed gears centre pin gets worn enough on the housing to let the gear twist out of alignment.

Re: Door locks only when open and on 1st latch
 

Mine has some wear on that pin but it did not SEEM enough to be causing the problem. Can only be sure if I remove the entire mechanism, but since I now have a solution, not a high priority.