One of the younger guys that works with us now told me this story. When he first hired on in the Elevator Business he worked for a non-union company and he went around cleaning pits and machine rooms for a long time, that's all he ever did. Eventually he assisted the owner in some troubleshooting etc. etc. until he got familiar with some of the equipment. So then one day they gave him boxes of titanium wire contacts and told him to go to a composite job and replace all of them in the controllers... Needless to say, when he turned the first car back on it wouldn't run... After hours of troubleshooting they got the car back running. I usually don't clean or replace contacts unless I know for sure that they are causing a problem - a very wise older Elevator Wizard gave me that advice.