Door locking problems - explained
 

Every few weeks someone has a question about their door being hard to lock with the key or unable to lock with the key. They usually don’t mention the knob is hard to lock too but that is inherent with the door key locking problem since the key and the knob interact on the same offending part.
Usually the problem arises after installing new door weather stripping.
Here is a picture of a latch that I cut away to depict the problem.
I have labeled the parts with a sharpie.
1, is the door latch pawl
2, is the door lock pawl
3, is part of the lock pawl which when locked, prevents the outside and inside handles from disengaging the latch pawl.

In the center of the picture, rotating on the round pin is the “toothed” latch/lock cylinder. This part is one piece and from this view you can see the “teeth” which are beveled on one side and square cut on the other. This part is rotated by the gear like teeth on the outside of the door which engage the striker plate on the door jamb.

The first picture shows the latch unlocked, the second picture shows the latch locked.

Re: Door locking problems - explained
 

The latch pawl and the lock pawl act upon the latch/lock cylinder slightly offset, not in the exact same place.
The latch pawl itself wears and so does the latch lock cylinder which causes the latch lock cylinder to rotate to where the lock pawl crashes into the tooth it’s trying to engage to lock.
You can feel the lock pawl crashing into the outer tooth by simulating door latche pressure on the latch with your finger while trying to engage the lock either with the key or the knob.
The center pin also wears and causes misalignment of the latch/lock cylinder. The center pin should be fixed and not move or rotate but most used latches the pin is loose and rotates.

So here is the quick fix, remove the latch from the door and grind some clearance into the lock pawl contact surface with a die grinder or dremel...or replace the latch.
I have a truck here that I acquired with a repro latch and it works fine and seems to be of good quality, brand unknown.
Grind the flat surface to the right of the “2” to prevent the lock pawl from crashing into the latch/lock cylinder tooth when latched. Grind enough so the lock pawl clears the tooth without contact.

Using your finger on the latching teeth to simulate latched door pressure you should not be able to feel the engagement of the lock, if you can feel the engagement there is not enough lock pawl clearance.

Re: Door locking problems - explained
 

Good write up!

Re: Door locking problems - explained
 

Another great info article Randy!

Thanks!

Re: Door locking problems - explained
 

Thanks guys.
Let me know if anybody actually puts the info to use....

Re: Door locking problems - explained
 

Hopefully this Sunday

Re: Door locking problems - explained
 

Randy
Perhaps you can help me with this...why when I have the door open, push down the door lock plunger down, then close the door; the door unlocks itself upon closing.

Re: Door locking problems - explained
 

my 68 Camaro does this by design (so you have to pay attention before you lock the car door) my truck does this and I assume it is for the same reason

Re: Door locking problems - explained
 

It’s by design, you can see in the picture that when the latch/lock cylinder rotates as the door closes it unlocks the door.
I didn’t know 68 camaro did that too, pretty sure 69 camaro doesn’t, been a while though since I had one of those.

Re: Door locking problems - explained
 

It's a neat feature of these models as you cannot lock your keys inside the trucks. ;)

Re: Door locking problems - explained
 

Thank you Randy. I did this repair today on my 72 Shortbed. I can now lock my drivers door with the key.
Mike

Re: Door locking problems - explained
 

So what was ur fix bro

[QUOTE=randy500;8081170]So what was ur fix bro[/QUOTE
I ground the lock pawl like you said. I could only lock door if I left it open 1/2 open but latched.
Posted via Mobile Device

Re: Door locking problems - explained
 

[quote=badd71;8081188]Thanks for the explanation, confirmed fix!