After 2 to 3 days the battery on my 95 SC300 drains so the car will not start. It appears to be a problem with the factory alarm system. The battery drain is in unison with the flashing of the dashboard security light. When that circuit’s fuse is removed the drain disappears. The battery and alternator were replaced before the actual cause was found. Can anyone offer a schematic or suggestion on how to fix this problem?

 

One thing...... in your handbook it says "if you do not intend to drive the vehicle for more than 48 hours (or something to that effect) TURN OFF the headlight switch. Do not let it sit in valet mode in the "on" position. This WILL drain the battery.

That's one guess.

 

If you can get your hands on a digital meter, consider checking these three steps...in hundredth of a volt.

1. Battery voltage with the doors closed and lamps off.
2. Battery voltage with the m0tor running at idle three minutes.
3. Immediate battery voltage with the mot0r switched off.

Expect more than 12.50 volts on step one, more than 14.20 volts on step two, more than 12.60 volts (slightly charged with more voltage than step one) for step three.
If the voltages are low, the alternat0r or it's internal voltage regulator is questionable. but if step two is good, than your battery needs charging first or it's defective.