when the timer unit is reset AND the extra ball trip relay is untripped, the only way to turn on the ball lift motor is via trough switch #8

when checking trough 8, make sure the timer unit and EB trip relays are reset. Also, use a ball to depress the rollover, not your finger since your finger may push the rollover down more than the ball can.

measuring a switch with a continuity test is not reliable. It will find opens, but things that look closed may still not work. Measuring the actual resistance using the ohms function is better as you can see the difference between almost zero ohms (good) and 2+ ohms (bad) ... but rarely it still won't work because the connection can pass small amounts of current, but not larger amounts.

the ideal ways to test the circuit is either using a jumper wire to bypass stuff or a voltmeter. In the voltmeter case, you want to poke around in a closed circuit when the motor should be running but isn't. One meter probe on wire 70, the other poking around in the circuit looking for where the voltage drops way below 50VAC.

tmi
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the purpose of trough switch #8 was to deal with the clever people who figured out that if you:
1] reset the game
2] shot a ball partway up the runway
3] pushed the manual lift button to raise another ball
4] repeat until four balls are in the runway
5] reset and cycle game to increase scores/features
6] shoot all the balls ... the game thinks you only shot one and you wind up with all 8 balls for the cost of the initial coin to reset the game

bally's solution was to not allow the timer unit to step up until all 8 balls were in the trough ... that's why if you reset with ball(s) in front of the shooter it/they will fall thru the playfield when shot and the next ball will close the shutter.

to make this work, they added trough switch 8 to detect all balls being in the trough.