The only thing I can recall about a 66 had to do with a brake problem. But since I worked on 3000's and 5000's I don't know which one that pertains to. You may want to check your brake voltage just to be sure. I think it was around 160vdc. also the normal brake ohmic value was in the 350 ohm range.One other thing I remember is I had a handrail chain rub a low voltage safety string wire intermittently, taking it to ground causing this type of error. Just a couple of thoughts.