That happened to me once! I found myself broken down on the side of the hiway with a failed sensor.I accidentally got a wrong polarity sensor installed, set the idle timing, and tried to check the power-timing. The light went berzerk.Then I remembered, the wire colors were different, and my little brain connected the dots. Years ago, I had found a polarity reversing patch-cord, which not knowing what it was for, I had thrown into the toolkit. Out it came and in it went. To my amazement, the idle timing was out to lunch; but the light was functioning again. So a quick reset and we were motoring again. This happened while we were quite a ways from home, and I was not looking forward to towtruck fees. Phewff!
