Trane XE 78 furnace coupled with Trane 1000 stopped working all together after running the AC one time. Everything worked overnight but stopped by the next morning. Wife heard a noise come from the AC unit (she says) that night. The furnace has the LED indicator that has no flash. No blower fan either. We used the furnace all winter, by the way, with no issues. I have checked incoming power to both units and all is fine there. Panel pressure switch is making also. Seems the AC unit is the culprit but logic tells me that if there was an issue with it then the breaker would have done its job and tripped before reaching the furnace. Both breakers for each unit were on when inspected. Control board is a Whites Rodgers 50A50. Ran a resistance test on the thermo and checked out. I also tried to jump the blower fan straight from the thermo by connecting red and white no fan. Had power to the transformer to controller but no power out of controller. What would cause it to blow?