Nuvatec 03/88 Isolator Relay Delay is a battery‑management module that monitors the main battery voltage (≈13.3 V on 12‑V systems) and energizes an isolator relay to connect or disconnect auxiliary batteries during startup. Common failure modes for this class of devices include coil burnout, tripped contactor due to over‑voltage, and internal fuse blowout; symptoms often manifest as a clicking noise, battery flicker, or loss of dual‑battery isolation. First‑check diagnostics: verify the main battery voltage with a multimeter, inspect the relay coil for continuity and signs of burn, and confirm that the isolator contacts are free of corrosion or mechanical binding. If the unit still fails, review any error codes from the vehicle’s ECU and test the relay’s output wiring to the auxiliary battery circuit.[oss-gpt-20b]