I had a similar issue with my score motor running because a coil in my score reel was dead so it could never return to 0 during the reset process. I used this link to help troubleshoot: https://pinside.com/pinball/forum/topic/williams-big-deal-help-please#post-2151431 You should be able to use that to figure out which switch is causing the motor to keep running. Then you'll have to troubleshoot the circuit associated with that switch because one of those switches will need cleaning/adjusting or maybe you have a bad coil like I did. I don't think you need to use electrical cleaner to clean contacts. Just use sandpaper or flexstone.

OK the thing with the wheels is called the score motor. Several things can start it running but several more things have to be set correctly for it to stop. Since it's not kicking a ball we can assume it's trying to reset.

Are all the score reels set to 0? If not it is likely that that reel needs to be cleaned and adjusted. If this machine has a bonus that unit needs to be reset as well. Finally the player unit needs to be set to the first player and then a ball kicked out.

If you can figure out how set all the reels to 0 and reset the bonus and see if that gets you further. This will also help identify the culprit.

You should read up on ems and their components here to get familiar http://www.pinwiki.com/wiki/index.php?title=EM_Repair

This video is brilliant and will show why it can be hard to get a pinball to reset: