Go to the stern, locate two black wires from the trim limit switch. They go into two connectors, one with a purple /white wire and one with two blue/ white wires. Unplug and jumper between the two connectors with a piece of wire. Try the trim switch. If it works your problem is with the trim limit circuit. Either the switch or the wires. If the wires look good the switch is probably dirty or corroded. You may be able to disassemble and clean it to get it working. Make sure to mark it well so you can put it back together in the same position.