This article addresses the most common HPLC detector failures and how to identify their source. It distinguishes between electronic problems, which should be resolved with the manufacturer, and mechanical or optical failures, which typically focus on the flow cell. Warning signs such as bubbles, contamination, or high pressure are also detailed, and critical maintenance aspects are mentioned, such as lamp status or parameter settings such as gain and response time. The text provides practical advice for diagnosing and preventing errors that directly affect the quality of chromatographic analysis.