Which of the following is a sign of a malfunctioning condensate pump?

A malfunctioning condensate pump is indicative of water pooling around the unit. Condensate pumps are responsible for removing excess moisture that results from the air conditioning or refrigeration processes. When the pump operates correctly, it efficiently drains water, keeping the surrounding area dry. If the pump is malfunctioning, it will fail to remove this water, leading to accumulation and pooling around the unit.

This water accumulation can potentially lead to other issues, like water damage or mold growth, making it essential to address the problem promptly. Therefore, observing water pooling is a clear sign that the pump is not functioning as intended. It suggests a failure in either the pump itself or a blockage in the drainage system, necessitating further investigation or repair.

The other options, while they may indicate different problems within the system, do not specifically point to a condensate pump failure as directly as water pooling does.