I've installed a Keetec car power door lock on my car. It works on four doors but even though it locks and unlocks the voltage on the actuators drops to about 7-8V. Problem is that the control unit for the fifth door requires 12V signal from the actuators to determine if the car is locked or not so the fifth door could not be opened if the car is locked. I've tried to lubricated the locks but that didn't helped. Do you have any ideas how to fix this problem?