motor will not trim down

[twotone]

Hi from middle georgia

I have a 1976 70 hp evinrude and today the down trim stopped working. the motor is now all the way up but will not go down. when i press the down trim button the relay clicks but the motor does not go down. when clicking the up trim the motor hums, but it does not move because it is all the way up already.
Any suggestions or ideas.

[boats.net]

Check wire connections, load test battery and check battery cables. may have a bad trim motor.

[spoutman]

had similar problem. Switch in shift and throttle control was corroded. Cleaned it and it worked fine.