magnet trim systems connect each of the two wires
from the trim motor to either ground or positive in order
to allow the motor to run in both directions.
If the motor will not run in the UP direction, it could be
either the UP relay in not making contact to 12 volts
OR the DOWN relay is not making contact to ground.
The opposite is true if the system will not run DOWN.
When the system is not energized, both relays
should connect the heavy motor leads to ground.
To test which relay is faulty if the trim system does not
operate in one direction