The remote isn't directional, it sends a pulse in every direction, but when you aim it at your chin, it somehow focuses that part of the signal as if your head was a satellite, I'm assuming.

 

The bone in your mandible is very dense and it bounces the signal like a laser and a mirror.

I'd guess the battery in the remote was going but you said you changed batteries. Maybe the battery contacts are corroded a bit in the remote? How old is your car battery?

 

yup the chin method works. works on cheekbone too i've found. press hard to chin if doesnt work