Assuming the door has not sagged and the striker is still in proper adjustment, the best suspect is the spring-loaded lever is not pivoting to lock the latch closed. That typically requires replacement of the latch assembly, but you can often get them working by spraying in some "Spray White Lube". That is Chrysler's name for their stuff, but you can find the same thing at any dealer's parts department, auto parts store, or hardware store. This is a lithium-based grease that sprays on very runny. The juice gets into tight places and takes the grease with it. Before long, the juice evaporates, and leaves the grease behind. This stuff works great for rusty door hinge pins.
Usually it is the grease that is causing the trouble. If the grease is thick and hardened, the spring-loaded latch will not swing into the latched position before the door bounces back open. It will latch if you hold the door fully closed for a few seconds, but that is nearly impossible to do against the force of the weatherstrip. A clue to this is it acts up in winter weather, but not in summer.
The old grease can also become impacted with road dirt. That will cause it to fail to latch in any weather. Give the Spray White Lube at least a day to do its job, but if that does not help, spray in some brake parts cleaner or carburetor cleaner to dissolve the old grease and wash it away. Give that a few minutes to fully evaporate, then spray in a light oil. I am familiar with Chrysler's "MP-50". It displaces moisture and will not evaporate. It does not have the heavy lubricating quality of Spray White Lube, but it will not get hard over time
When you use brake parts cleaner or carburetor cleaner, work the latch a few times to help it remove the grease, then let it air-dry right away. Many latch assembles use plastic parts and/or the hook that catches on the striker is coated with plastic. Some older cleaners will melt that plastic if it is left in contact too long.
Sunday, July 2nd, 2017 AT 12:17 AM