99 Taurus no start alarm issues

My 1999 Ford Taurus wouldn't start last night so now its stranded at work. The battery was weak and wouldn't start the vehicle. I tried to jump it but no go, the cables were in rough shape. A coworker had an extra battery which we swapped and the headlights came on and the horn went off continiously until we disconnected the battery. Also would not even crank when battery was connected. I have had alarm issues with this car in the past, and not wanting to start before (our key remote doesn;t work so we use the valet switch under the dash to start the car. I found a few answers online just searching but if anyone has some concrete answers please HELP!

If you have a valet switch under the dash and an alarm that goes off when the battery is connected, plus the starter won't even engage and turn over the engine, it sounds like you have an aftermarket alarm that is disabling the starter. This is not part of the original equipment and unless you can provide some details on the alarm system that's in the car, there's no way for us to give you concrete answers. Your best bet would be to remove the entire alarm system from the car, then fix any bad connections that were caused by the alarm install.

-Rod