I have recently encountered multiple failures of the Simplicity board on the York 3 to 6 ton package rooftop units (Sunline). This has been happening on many different jobs with the same units. The symptom is that the blower will not come on, even if the thermostat is set to fan "on". This causes the heat to lock out on high limit, resulting in a "no heat" service call. We even had a site visit from a factory representative from York. He was rather perplexed by the problem. He recommended that along with the new board we also replace the blower contactor, thinking that there may be a problem with the coil inrush amps. We changed the contactor along with the board and the board failed again 2 days later. There is a good seal around the electrical panel so we know water is not getting in. Have any of you experienced this same problem? I would appreciate any feedback on this.