My girlfriends '98 4 door 4x4 blazer started this a few days ago. Sometimes the driver door lock buttons don't work and doors randomly lock/unlock whenever - while driving, sitting in garage, etc. Thought it was key fob and removed extra fob from purse and removed batteries from both fobs (thought it was squished and pressing button), but it came back today. Had the back hatch open in the rain for a few minutes a few days ago, but it's not like that was the first time the hatch has ever been open in the rain. She just moved, so we packed it full of boxes a couple of times as well. Nothing else to speak of that could have initiated such a problem.

I found a few threads about locks here, but nothing like this problem. Bad switch? I thought short, but all of a sudden?

 

Body Control Module?

 

I would actually start at the faulty switch. It is possible that things have broken loose inside and are contacting at random. You may want to unplug the master switch (driver door) and see what happens with that unplugged. I'm not sure if you can, but you may be able to remove just the unlock switch from the master switch assembly so you can still control the windows.

 

Thanks everyone!

Body control module sounds expensive. I suppose I will start with examining the switch in the drivers door.