What the 1.5KE30ARL4G protects and where it sits
Its 25.6V reverse standoff voltage means it stays transparent on a 24V nominal rail, only clamping when a transient pushes the line above 28.5V breakdown. The 41.4V clamp at 36A peak pulse current is the voltage the downstream silicon sees — a downstream DC-DC converter rated for 60V abs-max has margin here, but a 40V-rated input stage does not.
Littelfuse lists the 1.5KE30ARL4G as Obsolete. No pin-compatible drop-in from the original factory is available; a functional replacement will require a different order code and possibly a package spin.
Thermal and mechanical fit
The DO-201AD axial body is a through-hole package — the leads solder into plated through-holes on the board, not a surface-mount pad. Operating junction temperature spans -65°C to 175°C, which covers the full industrial and most automotive under-hood ambient ranges. The Tape & Reel packaging suits automated insertion if the line still runs axial components, though many modern pick-and-place lines have retired the feeder for this form factor.