Not really a trick but dirty.. picked up 2 Westinghouse ERL cars and on one cars all 4 regulator fuses were jumped, had the wires off the fuse holders andtwisted together with wire nuts. The other car, if you put it on inspection would take off and run by itself only when the other car made a run on automatic .... when the salesman and super surveyed the job they said "I've seen worse". Luckily nobody got hurt.