NOTE: I've had the battery checked at AutoZone as well as by the mechanic that's taken care of the car since infancy. Both checks were done after the 1st incident. Both the battery and Alternator checked out OK.

The car is a 2003 RX300, 2WD, Auto Trans, 141k mi,

1st Time: I took an elderly friend to a Dr appointment about 3 weeks ago and I decided to stay in the car and read. I lowered the windows put the seat back and turned the car off but DID NOT remove the key from the ignition. I promptly fell asleep for the next 2 hours until my friend came out. When I tried to start the car it did nothing but click. We called a friend and started it with jumper cables. It started right away and I have had no problems since then even though it has, on several occasions, sat for several days without being started.

2nd time: This time I took my wife to the Doctors. The only difference between this time and the last is that I took the keys out of the ignition to make sure everything was off. Or so i thought. I didn't get out and see if the headlights were off. i just assumed they were if the key was out. All interior lights and displays were off.
Once again the car had to be jumped to get us home.

The only common denominator that I can think of is that I was in the driver seat reading or sleeping for a little over 2 hours both times. Can anyone shed some light on why my battery has gone dead when the ignition is off and the key is out.

I should note here that I keep my headlight switch in the ON position all of the time. My headlights come on automatically when I start the car and they turn of about 2 min after all of the doors are closed. Would my lights stay on because I was sitting in the drivers seat?

Your ideas would be most welcome.

ALSO: My radiator has developed a split in the tank. It's a very tight split and almost impossible to see unless the car is warmed up. Has anyone come up with a way to Patch a tank? If not, is DENSO still the go-to or is there something better I should look for that's not the ridiculously expensive "Lexus" brand.

Thanks,
Brian

 

Lights will go out after you open the door otherwise AFAIK they will stay on. There is no way to repair a plastic top radiator it has to be replaced.

 

Among the massive drain unstitched circuit [other than the headlights] are the brakes. If you put your foot on them they will quickly drain out the battery.

Salim