I have a Schindler 9300 escalator that keeps giving a D3 fault "phase failure" but will restart right away . Do the phase monitors breakdown on these? Can they be bypassed while a part is on order ?

I have seen them be problematic, and without a meter on them at the moment they trigger, you won't see anything. I had two that failed after 1.5 years in duty because the walk off plate was located under a skylight, and the controllers kept getting warm. They both failed within hours of each other. I thought at first I had momentary line dips from the incoming feed, but I traced it down to that component.

I would change it out prior to going any further just to eliminate that variable.

Good luck

Thanks