Remove the wires that go into the harness from the trim limit switch ('h' in the wiring diagram) and join the harness with a short length of wire. If your UP button now works properly you have 3 choices... 1) replace the offending switch. comes in a kit with both switches and their associated wires. Attempts to repair the switches usually fail. Also DO NOT just cut the wires and try and join the new switch onto the old wires. Merc supply the switch with its full wires for a reason... 2) remove the shorting wire and run with the system as is, being aware that to get the drive to trim or go all the way UP you need to press the TRAILER button. Most people don't do this one. 3) Leave the shorting wire in place and just use the UP trim button to get the drive UP. Being aware that with this configuration you can run the drive out of the gimbal support. Operate with caution. Replace the switches when you're doing other work on the gimbal area that will allow easier access, like when you go to change the uni joint bellows. This is the option taken by most people....
HTH,
Chris........
