My Prius is too "cool."

I have set up heat sensors outside my house for both security and for convenience of having the house's exterior lighting light up as I drive home on a dark night without having the lights on all night long on either a timer or dusk to dawn light sensor.
It works great when anyone walks by on foot or drives by the house after dark, but when I drive my own car by, it doesn't trip the heat sensor except maybe 1/3 of the time if I drive by the house at certain angle. I can walk by the house at the same spot in the road and it trips the sensor 100% of the time.
I assume it must be a weak heat signature coming from the car. Kind of annoying.

 

I just though of something. Maybe the sensor's detection areas are pointing a bit too high and the Prius is riding underneath undetected. Any adult person walking by would be taller than the Prius and the heat coming off their heads would trip the sensors. I assume this was not a problem with all the other cars driving by because the other vehicles have such a huge wake of heat coming off them that residual heat still trips the sensor no matter what.
I will try adjusting the sensors this weekend to point a bit lower so they will be aimed closer to the level of the engine compartment of the Prius this weekend and see if it helps.
The downside of this is, even it works, it will reduce range of the sensors.
I had conventional motion sensors before these new heat sensors, but I had to get rid of them because they would constantly be tripped by rain and branches moving in the wind. The new detectors are so much better in every way except for detecting my own car.