A penlight.
A shop rag.
A multimeter borrowed from the calibration shelf that he intended to return before dawn.
He didn't begin with the screen.
He started the way his uncle had taught him.
Elijah put his hands on the machine.
His right palm rested flat against the side panel above the drive housing.
He closed his eyes.
Warm.
A faint vibration from cooling fans.
Steady.
He slid his palm down the sheet metal to the heavy iron base.
Held it there.
Then moved toward the spindle housing at the front of the machine.
Both palms pressed against cold cast iron.
Elijah waited.
Beneath the fan noise was something faint.
So faint he never would have noticed it during daytime production.
Tick.
Tick.
Tick.
Not the smooth quiet of a machine at rest.
Something was out of true.
The ticking wasn't coming from the spindle itself.
It came from higher up, near a bundle of thin wires entering a sealed housing along the side of the head assembly.
Elijah knew that housing.
Thermal sensors.
Those sensors told the control system how hot the spindle was running.
If temperatures rose too far, the system shut down to prevent serious damage.
Right now, the machine believed the spindle was overheating.
Elijah opened his eyes.
Pulled out the penlight.
Moved toward the housing.
Six small screws held the cover.
He removed them carefully, one after another.
Then lifted the plate away.
Inside sat a row of connector pins.
The instant the light hit them, the ticking made sense.
One connector wasn't completely seated.
It sat just slightly loose in its socket.
Every time vibration passed through the assembly, the pin shifted against the contact.
Tick.
Tick.
Tick.
A loose connection didn't necessarily kill the signal completely.
That was what made the fault deceptive.
Just enough signal still passed through to make the circuit appear alive.
But the reading jumped.
Stuttered.
Spiked high for fractions of a second and dropped again.
To the board, those spikes looked like bursts of dangerous overheating.
So the board did exactly what it had been designed to do.
It shut the machine down to protect itself from a condition that wasn't actually occurring.
Elijah pushed the connector fully back into its seat.
Felt it click.
Then he looked closer.
Because connectors didn't usually work themselves loose without a reason.
Behind it, the small bracket supporting the sensor block contained a hairline crack.
Thin as a hair.
Running along one edge.
Heat had worked on the metal over months.
Expansion.
Contraction.
Again and again until fatigue created the split.
That crack had allowed the sensor assembly to move just enough for the connector to gradually back out of its socket.
That was the entire disaster.
A cracked bracket allowed a sensor to move.