'97 Eclipse GS Doors don’t lock

It almost sounds like the Lock Wire is not connected. Here is what I would do. Sit in the car and Arm the alarm. If you hear the Relay click for lock, It maybe a bad relay, wire not connected from the relay to the lock wire. does your sisters car have a button for lock and unlock in the car or was the door locks done with aftermarket motors? What Alarm do you have? Your question needs a little more information before someone could give you a good idea of what is wrong!

Well, when we push the lock buttons in the car, they lock and arm fine.  But if we try to lock the doors by pushing the button on the remote, both sides of the door do not lock.  We just hear a click but no locking....but the alarm still arms though.  The weird thing is if we lock the doors and arm the alarm, when we push the button to disarm the the alarm, the doors unlock.  So I don't understand why it works one way and not the other.

Not sure what kind of alarm you have? So here is some more information that might help you out. From the brain there are a bunch of wires in a large harness. Then there might be other smaller wires with 2 to 3 connectors. Most likely one that is colored Blue, one that is red and one that is white the white one would be a small set of wires that would have Blue, Green, Red wires most likely. If you have those wires the Green one most likely is for Lock. Follow that wire to the set of relays. Check that the 30 from the relay is connected and follow that wire to where is makes it's connection. It should be the weakest link. However Not all alarms are the way I have said in this post and the Blue wire might be for lock. It would be good if you had a DMM to check out your wiring. You could rent one from your local Tool Rental store. Or just take it to an installer. If you are in Washington State. Tacoma, Seattle, Port Orchard, Bremerton, I travel.