95 Automatic Door Locks

Hey Everyone, got something that just started happening. My car use to lock and unlock just find, locked when put in reverse or drive and would unlock when the car was turned off. Now it'll lock just fine, but never unlocks unless you hit the button. Is the setting somehow changed? Put an aftermarket car alarm in this weekend and ever since then its done this. Any help anyone could give would be appreciated, specifically how to check the programming and how to reprogram it. (Also need to know where I could find an owners manuel, can't seem to find one on ebay and the car didn't come with one.) Thanks.