I think/hope I've figured it out. I'll get back on it after the 4th. It has to have 12 volts to make the red light come on, there is no voltage in the pass through location you mention. I do have a couple of leaks there that need attention though. Mine is getting voltage, but the problem is the alarm sounds and the red light stays on all the way up to 120 pounds before it kicks off, then sounds off again when it drops to about 110 instead of waiting until it gets down to 60-65 pounds