Ok that is your problem. I think 87a should be +12V all the time. Ether the line to the relay has become disconnected or a hidden fuse is blown. If you put +12V on pin 30 of the relay socket you should be able to close your slides. Again I would jumper it through a fuse for protection. Use a jumper wire, connect to +12V, connect other end to fuse. Take second jumper wire connect to other end of fuse and other end of wire plug in to pin 30 of relay socket. I would use a 20 amp fuse, standard auto type. let me know what happens. I marked up the drawing with what you need to do.
With ignition on pin 85 turns on the relay which disconnects pin 87a causing slides to shut off. That is why it is present when ignition is on.