Upon arrival performed diagnostic. Found system to be non operational. Customer said she had friend try to diagnose system. Left wires unplugged and breaker off. Checked fuses they were bad replaced and turned power on, system did an electrical spark. Immediately turned system off. Found 4 wire not plugged in. There is no schematic to where wires go. System is very old, no model or serial numbers. Home owner said she wants to go through her family before she makes decision of replacing system. Would need a schematic to get wires back. Or asked home owner to ask friend where they go. System is non operational upon departure. Please send home owner hard copy.