If you remove the lead from the temp sender unit and the temperature gauge still moves to the hot end with the ignition key just turned to On, then there is an earth on the lead between the sender unit and the instrument cluster.
Perhaps this may be due the sender wire’s insulation being rubbed away, exposing the wire which is coming into contact with the body of the vehicle somewhere.
Here’s a link to the 94 Honda Accord System Wiring Diagram.
If you click on the view online pdf link at the bottom and then when the pdf opens scroll to the bottom of the page and click on the download icon (next to the zoom 100%) it will be easier to use.
When you have the document if you then scroll down to the Instrument cluster diagrams (p.23/50 in pdf) you will see that the sender lead goes as a yellow/green wire from the sender unit to the B9 terminal on the instrument cluster.
You need to trace the wire and check if the insulation is OK and /or that it hasn’t been shorted out to another wire or caught on some metal somewhere.
Here are two images taken from the wiring diagram that shows the connections
(click on image to enlarge for better viewing)
If you remove the lead from the temp sender unit and the temperature gauge doesn’t move with the ignition key just turned to On, then there is a problem with the sender unit.
If you measure the resistance of the unit when cold the resistance should measure ~140 Ohms (I think) and with a hot engine it should measure 30-50 Ohms