As soon as a battery cable is removed ( negative first ) the computer
programming is disrupted . The vehicle will need to relearn its idle , the preset
radio stations will need to be reset etc.
Disconnect the negative side of the battery
Unhooking the battery for about 20 minutes should be more than enough to resed the computer.
As soon as you take a battery cable off it will disrupt the computer program ( I understand that there is a item with a 9 volt battery in it that can be plugged into the cigarette lighter socket that maintains the programming ) You will not disrupt the programming, what happens is that learned items, such as engine idle characteristics radiao presets, and transmission shift patterns will be lost and will relearn on start up.
To replace the battery cables on a 1999 Mercury Mountaineer, loosen the connectors at the terminals. After this, remove the other end of the cables and install new ones.
Is your battery getting weak ?
On a 1997 Mercury Mountaineer : The " CHECK ENGINE " warning light is just to the left of the battery voltage gauge
had to replace the battery in my 2002 Mercury Mountaineer but now the theft light is blinking, it is cranking up. How can I stop it?
I BELIEVE the horn is mounted below the battery tray
I believe it is mounted below the battery tray in the engine compartment
On a 1997 Mercury Mountaineer : It came from the factory with either the Motorcraft BXT-65-650 battery ( or the optional Motorcraft BXT-65-850 battery ) ( that's BCI group size 65 , 650 or 850 cold cranking amps )
Disconnect the negative battery cable and then remove the positive cableRemove the battery heat shieldRemove the battery hold-down clamp boltLift out battery
Try disconecting the battery for 5 min.s and reconecting.