Marcus looked toward Gerald, because Gerald was responsible for the equipment and because the last thing he wanted was to become a man who wandered into restricted work on a guess. Gerald considered the request and stepped beside the cabinet. "He can observe and make suggestions," Gerald said.
"Nobody touches the wiring unless I've cleared it and the technicians handle the work." Marcus nodded at once. "That's fair. I wouldn't want it any other way."
He parked the cleaning cart away from the doorway and set his cloth on the handle. When he crouched beside the cabinet, he kept his hands on his knees and studied the labels inside. New digital interfaces covered older principles of switches, sensors, inputs, and protective decisions. He did not pretend to recognize the manufacturer's design from memory, and that fact made Luis visibly relax.
"Can you bring it through the normal startup sequence?" Marcus asked. Peter glanced toward the laptop. "We've restarted it repeatedly."
Marcus shook his head. "I don't want a reset. I want to watch what it does when you ask it to run, without clearing anything first."
Luis selected the authorized startup command while Gerald watched the cabinet. Green indicator lights appeared in a row, and the fan started with a soft mechanical rush. For several seconds the sequence looked healthy. Then one amber light flickered, the relay clicked, and the fan stopped again.
"There," Marcus said. He looked toward Luis. "What did the display say just before the fan quit?" Luis scrolled back through the log.
"Environmental disagreement. But it doesn't identify a faulty sensor, just a mismatch during initialization." Marcus nodded. "So the system doesn't know which reading to believe."
Peter lifted his head. "We tested the relay earlier. The coil is good." Marcus nodded again.
"I believe you. A relay can be doing exactly what it's told and still be the last thing you hear before a shutdown." The distinction was small but important, and even Peter let his arms fall away from his chest.
Marcus studied the temperature information on the laptop. One channel showed seventy-nine degrees, while the wall thermostat across the conference room displayed seventy-one. The system was designed to compare those readings before allowing the full demonstration ventilation sequence, and the difference exceeded its permitted range. Each individual value was plausible on its own, which explained why the ordinary diagnostic alert did not name a broken part.
"What is the actual room temperature?" Marcus asked. Natalie walked to the wall thermostat and read it aloud. "Seventy-one."
Gerald checked a calibrated handheld meter and found the room close to the same reading. Luis stared at the second temperature channel. "Seventy-nine. It hasn't moved more than half a degree all evening."
"If the reference channel is drifting," Marcus said, "the controller may be refusing to trust the startup. The relay might be dropping because the safety check is doing what it was built to do." Peter frowned, looking between the two readings. "The computer treats seventy-nine as believable. It's not giving us a sensor failure warning."