I’ve had a 1991 rx-7 sitting in a barn for about 15 years. Upon installation of a new battery all the electronics functioned, the lights lit up, the air conditioning ran, the dash turned on, everything functioned as it should. Even the engine turned over. After pressure washing the vehicle I noticed that the dash lights would not turn on. It emitted a beeping noise that degraded in volume as the vehicle lost power. I’ve tested the battery and the fuses, they appear to be fully functional. Im new to working with cars so any help would be very much appreciated.