Have a simplex 4004-9101 from 5/09/1996
Strange issue after electrical spike to building. We lost internet modem and router in nearby cabinet from surge. Building was found with horns going off in 2nd story but no alarm zone noted in panel. Reset did not clear condition. Pulled ac power and batt for 2 mins.
On power up unit alarm is cleared but the trouble circuit (screw 8) has 24vdc + on it however the panel has zero trouble codes listed. Also the trouble led is off. Unplugging ac or batt does produce expected trouble code.
Tried power cycle again
Tried reset, unit appears to reset but trouble signal on screw 8 comes back.
Need ideas on what could be triggering trouble signal out but no indication of trouble on display.
Thank you