I recently replaced my battery in our 1998 Expedition and when I was reconnecting the + terminal the alarm went off. I pushed the two buttons on my remote (activate and deactivate) and the alarm went off, I continued to install the battery.

Now, the alarm doesn't automatically activate when I lock the doors with the remote or via the automatic door locks.

I have tinkered with the 'valet' button and the 'deactivate/reset' button in the cab, messed with the buttons, etc. I have no idea what to do to get the alarm back on and working.

Any help would be appreciated! Thanks!

 

Is this an aftermarket alarm ?

 

This is a Code Alarm brand alarm. My understanding was that it was installed at the factory.

 

Not "factory" , dealer maybe . Ground issue? I disconnect a lot of aftermarket alarms because of failures . Improper battery connections (neg before pos ) Voltage spikes can fry them . If you do not have a Ford key fob to control the remote , it is aftermarket .