How to fix a jack plate that will only run one way: First check and replace the 40-amp fuse. The 40-amp fuse is located on the red wire that comes from the relay harness and is connected to either the (+) battery post or the main power switch. Depending on the year your jack plate was made the fuse holder cover will be either blue or black. For best results, replace the fuse even if it does not look blown.
If your jack plate still only runs one way, but not the other, jump the power cord directly to 12V battery.
Follow the black power cord coming out of the unit’s motor to the disconnect point. Disconnect the blue and green wires from the relay harness. Now the green and blue wires can be directly jumped to a 12V battery by touching the green wire to the positive post of the battery and the blue wire to the negative post of the battery at the same time. Reversing this connection will run the unit in the opposite direction.
If your jack plate still only runs one way, but not the other after you’ve replaced the fuse and tried jumping the power cord, it is likely that the actuator needs to be replaced.
If your unit is less than three years old, contact T-H Marine for a replacement. If your unit is more than three years old, contact your local boat dealership or contact a retail location for a replacement.