I have worked out a problem with the chasing lights in the topper. I thought the problem was on the chase light board in the backbox. However I have tried a different power driver board and now the lights are working properly. So the problem is on the power driver board. I have checked the manual and there are two solenoids that control the chasing lights. As you can see in the image the solenoids 27 and 28 control the chasing lights board.
I need your help here. I don't know what 27 and 28 are. Are they the transistors Q27 and Q28? Otherwise, what are the numbers 27 and 28 referring to?