The Nuvatec 1987 Isolator Relay Delay is a battery‑management module that senses main battery voltage and energizes an isolator relay when the voltage exceeds a set threshold (typically 13.3 V on a 12‑V system). Common failure modes include a burned or cracked PCB area around the delay circuit, a failed coil or driver transistor, and loss of control signal from the upstream controller. First‑check diagnostics: verify that the battery supply is within spec and that the relay’s control input receives the correct logic level; visually inspect the board for burn marks or component damage; then measure the coil resistance and test the driver transistor with a multimeter to confirm proper operation before proceeding to component replacement.[oss-gpt-20b]