Now, in the image forming apparatus, the connectors may be manually switched to rearrange the flow path, for example when replacing the ink tank unit, doing the maintenance work, or discharging a transport liquid from the ink tank unit loaded with the transport liquid, and refilling the ink tank unit with the regular ink. In such occasions, the connector may be wrongly connected, or left unconnected.
The existing image forming apparatuses are only configured to detect that the connector is unconnected, as result of detecting whether the connector is connected, and not configured to detect that the connector is wrongly connected, in other words the connector of a different color has been connected. Accordingly, the user is unable to be made aware of the wrong connection of the connector. In case the user continues with the mentioned work without the wrong connection of the connector being detected, just reconnecting the connector is not enough, but a large-scale repair work will be necessary for the target unit of the connection (e.g., ink tank unit) or a unit ahead thereof (e.g., ink jet head).