If a coin door switch was stuck, the credits would be going up (not down). If the game is repeatedly subtracting credits then it sounds to me like the coin relay (AKA the start relay) is stuck on. I would check that first.

- TimMe

From your description, the rear stepper unit selects the current player up. That would make the other unit the coin unit, which is used to decide how many players are playing. At the start of a new game, the coin unit should reset to 1 player. Each time you press the credit button (assuming you have credits) this unit should step up once to add an additional player, and also subtract a credit from the replay unit. When you get to 4 players, a switch on the coin unit should open to shut off the credit button.

The credit relay should not be staying pulled in. It should pull in when you press the credit button, run the score motor for one cycle, and then drop out on its own. It's likely that the reason you are always getting 4 players is because the credit relay is stuck on, which would advance the coin unit up to 4 players after four score motor cycles.

There is a lock-in switch on the credit relay that is supposed to keep it powered up for one score motor cycle. There is a score motor switch that should open at the end of each cycle to interrupt the lock-in circuit and allow the credit relay to drop open. I don't have a Pat Hand schematic, but on the Satin Doll schematic this shut-off switch is on the #5 cam. You may want to check the switches on this cam to confirm that they are all operating as they should.

- TimMe

Another possibility with the credit relay sticking is that it is getting mechanically stuck. If there is a lot of gunk on the relay armature and the face of the coil, the relay may sticking for that reason. Cleaning off the gunk with alcohol or metal cleaner should help. If the face of the armature has a severe indentation stamped into it from repeatedly striking the coil center pole, you'll need to grind or file the indentation so that it doesn't have any edges that can get hung up on the coil.

- TimMe

Just to be clear, the rear stepper in this era of Williams games is usually the Coin Unit, which keeps track of the number of players. The spider on the back of it has a lot of fingers on it. The front stepper is usually the Ball Count (or Count Ball) Unit that keeps track of which ball number you're on. It usually has just two fingers. Both bakelite plates confusingly refer to themselves as Player units. It could be different on your game, but it'd be unusual for the time.

The schematic for Pat Hand is here: http://mirror2.ipdb.org/files/1767/Williams_1975_Pat_Hand_Schematic_Diagram_continuous.pdf

As TimMe said, the credit relay should be dropping out on its own after one cycle. It's a little odd that it stops trying to subtract credits after it reaches the zero credit break switch on the credit unit in the backbox. It seems like it should keep trying to deduct credits anyway.

One thing you might try is putting the score motor into service mode and manually rotating it to see just what's triggering/tripping/changing around the game as the score motor advances. There are a few normally closed switches on the score motor that are meant to hold on the credit relay and drop out as it turns, maybe one of them is staying closed.

Cam 5, switch A, in particular, is in series to the Credit Relay. If it stays on, instead of coming open, and the Credit Relay has pulled in once, then the Credit Relay will stay on and never drop out.

Cam 1, switch D is in the circuit that pulses the credit unit reset, which steps down a credit. It should be normally open and close as the score motor runs.