The trim sender is the round module on the starboard side of the gimbal ring. If it is the original it is a wire wound variable resistor. Go to the stern and locate the wires coming through the transom (not the trim limit which connects to b/w and p/w wires). Unplug and measure the resistance with an ohmmmeter. If it reads open the you either have a dirty contact or broken wire. If you read resistance, run the drive up and down to se if it changes. If it does then it is probably your gauge. If it reads open you can take it off and open it up to see what is wrong. You might be able to clean it and get it to work. Good luck.
