You'll want a copy of the schematic. It can be found at https://ipdb.org/machine.cgi?id=1677

Is this a new problem or did you buy the machine this way?

What is your skill level with repairs? Do you have a multimeter and know how to use it?

Hi wickedpin
in post-1 You write +/- "On player-2, -3, -4 unlit spinner gives 10 points --- lit spinner gives 100 points" - do You have the pin set in "5 balls per play" mode ?
In post-1 You write "On player-1 a spinner gives (lit or unlit) 1100 points" --- is this a "typo", did You wanted to write "110 points" ? Here https://www.ipdb.org/showpic.pl?id=1677&picno=10511 we see the spinners and an "Left Thumper Bumper", "Center Thumper Bumper", "Right Thumper Bumper". See the JPG --- the left thumper bumper and the left spinner share "wiring" --- what happens when You hit left Thumper Bumper ? (Same on the right) Greetings Rolf

0Night-Rider-Work-21 (resized).jpg

Start by tightening all switch stack screws on all score reels. First the screws closest to the contact points, then the screw closest to the wire tabs.

Next, investigate that the Player-up Unit works smoothly and that the wiper fingers are centered on the contact plate points whenever Players 2=4 are "up".

Hi wickedpin
You are right - I mixed up players --- correct is "player-1 functions and players-2, -3, -4 are faulty".
I fear troubleshooting on the problem as I have no plausible theory. In a four-player-pin the stuff to do is separated - a ball on the playfield makes action to happen --- a Points-Relay is made to pull-in --- then completely separated is "which Score-Drums / what player gets the points". The JPG in post-4 shows: Make-and-Brake-Switches on Cam-12 either let the 10-Point-Relay or the 100-Point-Relay to pull-in.
You did not yet answer my question about "what happens when You hit the left or the right Bumper when player-2, -3, -4 is playing". One more question: Player-2, -3, -4 can play and make points - ONLY the spinners are faulty ? Greetings Rolf

Hi wickedpin
I join MrBally - his post-6. I have never seen the inside of an "Night Rider" - here https://www.ipdb.org/files/1677/Bally_1976_Night_Rider_Manual.pdf on page-13 I do not see the Player-Unit drawn (in the cabinet) so I clue the Player-Unit is mounted in the Backbox. Greetings Rolf

Hi wickedpin
thanks for the picture. On the right, somewhat down I believe to see the Player-Unit. Start a One-Player-Game then look at the wipers and the rivets. Danger - Your pin has (110VAC) 48 VAC for actuating coils, 6VAC for the lamps - electricity can kill You --- never touch bare wires / solder lugs. In a One-Player game the wipers should sit in the center of the rivets. Then start for second player, third player,fourth player. Then play Player-1-Ball-1 and let the ball drain, the pin steps to Player-2-Ball-1 - now look at the wipers and the rivets --- in this position (Player-2) : Do the wipers sit in the center of the rivets ? Play Player-2-Ball-1, the pin steps to Player-3-Ball-1 - now look ... then Player-4-Ball-1. Then toggle-off the pin, toggle-on, start a One-Player game, then toggle-off - now try to step manually the Player-Unit --- some slack in the movement ? Do it again, manually reset the Player-Unit then manually step up --- always good ?

Screws on Score-Drums: There is a mechanic hold on each Score-Drum - unlock and take a Score-Drum of Player-1 out, turn it and let hang on the wires. TRY with a Screwdriver: Are the screws on the switchstacks on the Score-Drum tight ? Then do also "a Score-Drum of Player-2".
IF (if, if) You have found loose screws: Write down on which Score-Drum You tighten the screws - check (and maybe tighten screws) ALL Score-Drums on ALL Players. Greetings Rolf

No. The two screws on the switch stacks of each ( of the sixteen ) score reels.
Switch stacks. Wires closer to one of the screws. Contact points closer to the other screw.

See a Bally part catalog or the booklet titled "An Introduction to Bally Flipper Games".