Ok, found the factory alarm battery! It's under the right side cover. Remove the cover, remove 2 screws holding the ECM, REMOVE THE 2 nuts holding the plastic cover and the alarm module is snapped onto the back. On side of the module is potted. The other is a snap on access panel. Instructions are on HarleyDavidson.com under alarm battery ( 9V Nickel Metal Hydride). I bought mine at batteries plus. You have to silicone grease the contacts, have some available, and reuse what's already there..


Two screws remove the ECM. Two nuts remove the plastic housing. Alarm module snaps out the back after unplugging it.

The factory battery lasted 16 years. The alarm would go off at random times while riding or while parked.......

 

SEARCH HD SITE FOR Smart Siren Battery Replacement Kit.
GOTO THE "GUIDES" TAB: you'll find a link to iillistrated instruction on how to open the battery box side of the security module:

Battery replacement, Smart Siren
1.
See Figure 1. Remove the battery cover (2) from the siren box as follows:
a.
Place the siren on a sturdy, flat surface with the potting (1) and battery cover facing up.
b.
Using a blunt, stiff blade such as a table knife, insert the blade between the case and cover at a 45 degree angle to the side of the case. Insert the blade until it touches the snaps on the inside face of the cover. Figure 2 shows the four barbed snaps (2).
c.
Twist the blade slowly so the inserted edge presses against the inside face of the cover. The cover will pop off and can be replaced later using silicone adhesive if necessary.
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1 Potting
2 Battery cover
Figure 1. Insert Blade Between Case and Cover (Smart Siren)
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1 Battery cover (underside)
2 Snap with barb (4)
3 Cover seal
4 Foam cushion pad (glued in place)
5 Battery
Figure 2. Remove and Replace Battery and Seal (Smart Siren)
2.
See Figure 2. Raise the top flap on the foam cushion pad (4). Remove the old battery (5) from the siren box, and gently unfasten the snap connector from the battery. Save the grease coating the terminals.
3.
Obtain the new nickel metal hydride (NiMH) nine-volt battery from the kit. Coat the terminals of the snap connector and the new battery completely with the grease from the old connection.
NOTE
If not enough lubricant remains to completely cover the terminals, Electrical Contact Lubricant (Part Number 99861-02) is compatible, and is available from a Harley-Davidson dealer
4.
Snap the connector onto the new battery, and install the battery into the siren box.
5.
Replace the old cover seal (3) with the new seal from the kit, inserting it fully into the groove of the battery compartment wall.
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1 Press cover down and left
Figure 3. Align and Center Cover (Smart Siren)
6.
Lay the top flap of the foam cushion pad over the top of the battery.
7.
Replace the battery door cover, using silicone adhesive if necessary.
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