When testing a vacuum door actuator, what does a zero reading on the vacuum gauge indicate?

A zero reading on the vacuum gauge indicates that there is no vacuum being applied to the actuator. This typically suggests that there is a vacuum leak in the actuator or the associated vacuum system. When a vacuum component, like a door actuator, fails to hold a vacuum, it cannot perform its intended function of opening or closing the door properly.

In a functioning system, the vacuum gauge should show a positive reading when the vacuum is applied to the actuator, confirming that the actuator is functional and capable of moving the door. Conversely, a zero reading signifies that the actuator cannot hold the vacuum, directly implying a malfunction in the vacuum seal or lines. This situation necessitates further investigation to locate the source of the leak or to assess the integrity of the actuator itself.