This was extremely disappointing. I have had a version of this for both of my cars for the last few years. One of them seemed to be dying so I bought this as a replacement. The difference was startling. My old one had a reliable green, yellow, red sequence. Red came on reliably at the same point. This unit did not. The picture with the light pushed through the garage wall that someone posted said it all. It is completely unreliable. It usually does nothing until the red light comes on and then you have no idea whether the car is in the right spot or not. I took it off and repaired my old unit instead.