Im not sure if this would be the right place to ask this question. I apologize in advance if this is not the right area. If I indeed placed this in the wrong area, if someone knows a better suited area I would be more than hsappy to put it there. Thanks in advance.
For whatever reason I have seen many 3rd gens over the years, some of my own, and this seems to be a fairly common issue. The keyhole in the door locks will stop working. Usually in the cars with the power locks. Dont recall if I saw it on a non "power" lock car. Its usually the driverside door. As is the case with both my birds. One being a 87 TA and 89 Formula. In both I can get the key to either go all the way or most of the way but it wont turn in either direction. Now Im fairly certain theres nothing wrong with the actual locks, just the keywhole mechanism I guess. Because they can both be locked and unlocked from the inside and the power door buttons work also. So both manual and with the power buttons the car can be locked and un-locked from the inside. Normally the passenger works fine, as was the case with both cars until recently. On the 89 bird the passenger side recently started screwing up. I was wondering if anyone knew what the problem might be or if they have experienced similar issues.

 

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My pass side lock (power) acted as you describe. The cylinder was frozen from lack of use or lubrication. After replacement, all was well. Lock-Ease or a similar product will eliminate the problem in new locks.

JamesC