I have a 1997 volkswagen Golf, the passenger door won't open when it's cold. I've had the car for a few years and every winter the door just won't open. Also, sometimes, when it is moderately cool out, the outside handle will work but the inside handle will not. Occasionally, if you push on the door really hard, then it will open from the outside, I assume it's from changing the pressure on the latch. I've tried cleaning the latch with cleaning solvent and lubricating it with wd-40, although, neither seemed to have any effect. Also, I've taken the door panel off and there appears to be some vacuum tube attached to the latch mechanism, which may explain why it temperature is affecting it. In case it makes a difference, it is a 4-door and 2L.

Figured it out. Also, I'm op.
Step 1: remove the inside door panel. (put a rag or towel in the bottom of the door in case anything falls down the door.)
Step 2: remove the the 4 bolts that hold the latch, and the outside door handle.
Step 3: remove the outside door handle.
Step 4: remove the vacuum tube and electrical wires from the latch.
Step 5: take off the bar that connects the latch to the inside handle.
Step 6: remove latch mechanism (you'll probably have to loosen the window rails, don't unscrew the top one all the way.)
Step 7: take the latch apart. there is 1 screw and 3 plastic locks.
Step 8: figure out how the latch mechanism works, see if you can fix it. In my case there a bar that is supposed to move up when the door is unlocked. It wasn't moving up, so it just needed some lube.

put it back together by doing the steps in reverse order. Figured it out. Also, I'm op. Step 1: remove the inside door panel. (put a rag or towel in the bottom of the door in case anything falls down the door.) Step 2: remove the the 4 bolts that hold the latch, and the outside door handle. Step 3: remove the outside door handle. Step 4: remove the vacuum tube and electrical wires from the latch. Step 5: take off the bar that connects the latch to the inside handle. Step 6: remove latch mechanism (you'll probably have to loosen the window rails, don't unscrew the top one all the way.) Step 7: take the latch apart. there is 1 screw and 3 plastic locks. Step 8: figure out how the latch mechanism works, see if you can fix it. In my case there a bar that is supposed to move up when the door is unlocked. It wasn't moving up, so it just needed some lube. put it back together by doing the steps in reverse order.