2000 Buick Park Ave. Ultra


all at the same time a/c quit working, fan controls work, interior lights do not come on, security light on all time, both check engine & service engine lights came on but went off same day, i have checked all fuses i believe all are ok found 4 fuse boxes what is wrong? Took car to AutoZone to have CEL reading read as suggested and nothing showed up. What should I do now?