What action should a technician take when the pilot assembly orifice of a spark ignition furnace is completely clogged?

When the pilot assembly orifice of a spark ignition furnace is completely clogged, replacing it is the most appropriate action. This is because a clogged orifice severely restricts the flow of gas, which can lead to a failure in generating a reliable pilot flame, necessary for the furnace's ignition process.

Cleaning may seem like a quick fix, but if the orifice is entirely obstructed, simply cleaning it might not restore its optimal functionality, especially if there are deposits or damage that compromise its structure. Adjusting an orifice generally pertains to modifying its size or gas flow, which is unnecessary and potentially harmful if the orifice is compromised. Disconnecting it would eliminate the pilot function entirely, preventing the furnace from operating safely. Therefore, replacing the orifice ensures that the furnace can operate safely and efficiently.