Re: 156 Alarm and remote not sync
there are 2 possibilities, either you have a constant drain, or the alternator is not charging the battery so you have run it flat.
you can test the alternator by measuring the voltage across the battery, it should be 14.4v with the engine running and no electrics switched on, and at least 13.99v with all electrics switched on (demister, radio, lights, etc). if it is lower it means the alternator's output is not sufficient to charge the battery.
you can test for a drain on the battery using the folowing method:
1. Remove the negative side battery cable.
2. attach a 12-volt test light between the negative cable and the negative battery post.
3. wait a few mins, then if the bulb is bright it means something is using too much battery power.
4. remove fuses one at a time, if the light goes out or goes a lot dimmer it means you have found the circuit that is causing the drain. examine that circuit carefully for shorts or faults.
EDIT: actually there is a third possibility, the new battery you bought may have failed prematurely, its very rare but it can happen. if the alternator and drain tests do not find anything then consider this.