That is actually one of my suspicions. Unfortunately, work has been nuts and I have been unable to pursue this at all this week. The last thing I did was run a new ground wire to the AP1. I need to re-ground the Stebel and test a new connection to the AP1. You have to remove 13 screws in order to remove the top cover and left side cover. While that is not an overly large number, try doing that 2 or more times in a row (BTW you have to re-insert them too). It gets old quick and consumes time in a limited evening. Since I have the horn working (which I actually had to use on the way home last night-- car drifted onto the line next to me) I am less manic about solving the AP1 issue. I will get there.