Update but no resolution
The car alarm installer thinks I have a bad alternator, he got a reading of 12.3 V while the car was running and said it should be around 14.0V. So he didn't uninstall the car alarm system. I'm picking up the car tomorrow and bringing it to my mechanic who said he will check the alternator and voltage regulator. Now I don't know who or what is the blame for my car not starting.
But this still doesn't make sense to me. What does a bad alternator have to do with a battery that is in park? It still seems that something is draining juice from the battery. So does the alternator or voltage regulator have any purpose while the car is off and in park? Does the alternator still hold a charge while in park and does it have to be more or less than what's in the battery?
Only four hours after I put in the new battery, the alarm LED light and the dashboard clock stop working meaning there's not enough juice to keep it going. I did drive the car for 15 min on the highway after I put in the new battery; therefore, if it is a bad alternator then that 15 minute drive might have been running all on battery then, right? Is it possible for a battery to discharge so much that a little LED light stops blinking?
Who, what seems to be the culprit here? A bad alternator or a bad car alarm installation or is it something else even?
Thanks in advance for any input!