Frozen door lock cylinder - suggestions?
 

Despite repeated use of penetrating oil the RH door lock cylinder in my 99 k2500 is still “frozen” such that twisting the key won’t rotate the cylinder. I can unlock it from the inside and the remote actuator works fine.

Unless anyone can give me some other suggestions I’m assuming I’ll have to disassemble the door to access the cylinder for (presumed) rust debridement.

Anything else to prep for if I disassemble the door? Clean, grease, and lube the moving parts? I’ve not yet dug inside the door of a GMT400.

Re: Frozen door lock cylinder - suggestions?
 

Here's a picture of the back of the handle. They're kind of a pain to get out of the door. You press the tab on the bottom the screwdriver is pointing at and the lock pushes in (up in the picture) to remove it.

Re: Frozen door lock cylinder - suggestions?
 

Pry up the power window/lock assembly and remove the connectors. Two screws in the arm rest, 4 tabs on the interior handle bezel, and a bunch of clips hold the door panel on. You have to pop off the little panel by the mirror first. Do it with the window up. Don't forget the courtesy light connector.

Once the panel is off, the exterior handle is held on by two 10mm bolts. A wobble adapter and a magnetic socket will be your friend for the one inside the door frame. Once the handle is loose, you can slide it out a little and release the rod from the pawl for the lock, then gently pull and twist it out. It takes some practice and is a tight fit. Tape the edges of the handle opening before you fully remove or install the handle if you're interested in keeping your paint job intact.

Re: Frozen door lock cylinder - suggestions?
 

Thanks guys. I appreciate the advice.

Re: Frozen door lock cylinder - suggestions?
 

Finally got around to tackling this. The cylinder is out. Odd, it rotates freely but over a very limited distance from say 12 to 12:30. Still fiddling with it.

EDIT: I realized the cylinder could be further disassembled. It looks like the wafer closest to the keyhole is fixed in an elevated position blocking rotation as it remains within a “trough” located in the sleeve that encases the lock set.

Re: Frozen door lock cylinder - suggestions?
 

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Can you post a picture of the key out of the lock cylinder? Does the wafer move at all when you insert or remove the key?
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Re: Frozen door lock cylinder - suggestions?
 

Leon thanks. I can but the wafer stays in the same location whether or not the key is in place. I tried applying pressure to the wafer but it stayed put. It’s the only wafer poking out as such.

EDIT: added photo sans key

Re: Frozen door lock cylinder - suggestions?
 

I wanted to see a picture of the key by itself also. What happens if you hold that wafer down while inserting the key?

Re: Frozen door lock cylinder - suggestions?
 

When I went back for this photo I was able to push the wafer down without a key in the cylinder after which I was able to freely rotate it inside the sleeve repeatedly with key reinsertions and removals. Maybe the carb cleaner I tried earlier dissolved some confounding old grease or graphite.

Any chance a thorough degrease and relube would have this working as it should? I’d hate to reassemble the door for the problem to recur.

Re: Frozen door lock cylinder - suggestions?
 

In your previous pictures it doesn't look like the key is inserted into the lock all the way. It could be that one of the wafers was stuck. Yes, I would try the degrease and relube and see how it responds. I would use a lube or penetrating oil with teflon in it.
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Re: Frozen door lock cylinder - suggestions?
 

Check. Thanks. What solvent would you recommend? Carb cleaner, brake cleaner?

Re: Frozen door lock cylinder - suggestions?
 

The good news is, it’s rotating freely and well lubed. The bad news is, it rotates with the key only partially inserted and even with a screw driver. There’s no wafer barring the free rotation of the cylinder with the key removed.

Re: Frozen door lock cylinder - suggestions?
 

Each wafer has a tiny little coil spring in a pocket.
The wafer that doesn't want to drop may be missing a spring from corrosion.
Strattec used to sell lock cylinders, springs, and wafers for the GM T400 trucks. I don't know if they're still available.
If you have a local locksmith that's an old timer he may have the correct wafers and springs in his parts hoard.
Your other option is to get several door locks from salvage vehicles and pillage the internals to build up a lock cylinder.

The Wafers should be stamped with numbers 1-4. I think I'd make a sketch in a notebook. Then pull each individual wafer and write down the numbers on the sketch.

EDIT** The T400 chassis GM 12549131 Door lock cylinder kit is $41.18 but I bet shipping makes up the $20 discount and then some. I'd check locally first.
https://www.gmpartsdirect.com/oem-pa...inder-12549131

Notice the illustrations don't show wafers or wafer springs just the covers and cover springs. I would ask the parts guy at your dealer whether it includes wafers and springs.

Re: Frozen door lock cylinder - suggestions?
 

Thanks for the info! I did get a GM (US made) replacement lock and a local smith was able to re-key that without any problems. I also purchased a GM replacement latch as the OE example had a torn up inner plastic buffer piece. Now it's time for re-greasing an re-assembly.