First I would remove the dash switch and make sure the harness doesn't have any connectors loose on the back side. If no problem there,pull the instrument cluster and find the connector for the cruise harness. It should be a brown connector with 3 wires,I forget the colors. Check that connection for any loose wires.
If neither of those are your problem,the next step would be to remove the RH lower cowling. Once removed you will be able to see the relay and diode for the cruise harness. Either could be bad or could have connection problems. Not sure how you test them since we always had plenty we just swapped parts out.