Need help on my Grand Prix, resets but says game over

By jetmechinnc

6 months ago


  • 11 posts
  • 6 Pinsiders participating
  • Latest reply 5 months ago by franz
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#1 6 months ago

I'm hoping it is something simple. My Williams Grand Prix has been perfect for about a year now. My friend was playing it and went to start another game and when the game reset, it said game over! The game still requires quarters, so I first thought it just needed a quarter when he told me about it. But with credits showing in the back box, you can hit the start button, the game resets all of the score reels, and then promptly says game over. Any suggestions? Just odd that it was working perfectly, then when he went to play the next game, it failed.

Thank you,

#2 6 months ago

When you push the credit/start button does the ball kick to the shooter lane? Or does the machine start to reset, and all the score reels reset to zero, but then the reset process just stops? Something simple to check: make sure the outhole switch under the playfield is clean and adjusted properly...

#3 6 months ago

The ball does not kick out. The machine resets all the score reels to zero then just stops with the game over sign illuminated.

#4 6 months ago

Does it go into tilt? Maybe check the tilt Bob and make sure it's free.

#5 6 months ago

This type of issue is almost certainly a single switch gap or a loose screw causing the issue on one component. Dont go crazy fixing things that are not broken and introduce new problems- resist the temptation to "just look around and fix anything that looks weird". I have caused myself issues doing this!

Dont have time to look now but schematic is the way forward! They are on IPDB and are FREE!

#6 6 months ago
Quoted from Lermods:

Does it go into tilt? Maybe check the tilt Bob and make sure it's free

No, it doesn't say tilt, just game over. Goes through the motion of resetting all the score reels, then just says game over, and never pops out the ball into play.
So busy at work, hopefully I'll get a chance to look at it Monday. I already have had to use the wiring diagram for one issue. So hopefully I can figure this out.

#7 6 months ago

Does it advance the ball counter? If I remember correctly, part of the start sequence involves pulsing the ball advance or whatever its called. Its a disc looking thing with a bunch of contacts on it. Grand Prix has 4 I think. When its in the "0" position, it triggers the game over relay. If the coil that advances it isnt being fired, or, if the mechanism isnt moving the disc, it could cause this.

#8 6 months ago

Schematics and manual suggest latch relay on game over relay as a probable cause.

Check to see if the latch relay works mechanically and watch to see if it engages. If it engages its probably the hold swith- if it does not you can look at stack 1a on score motor or reset relay or coin relay as they are in oath of latch.

#9 6 months ago

Well apparently there is a issue with the game over latch relay. Realized this when I noticed the lock relay engaged. Should be a momentary thing and it was staying engaged. When the game restarts, the game over latch relay doesn't pull and the game stays in reset mode. Found this out when I hit the drop targets, they kept resetting. If I manually trip the game over latch relay, the game plays perfectly.

I think the game over relay coil is the problem, P/N Z 27-1000, it ohms out at 2.4 ohms, compared to another one in the game that is around 10 ohms.

I need to review the wiring diagram and see what powers this coil. Not sure, but per the description reset cycle, it sounds like it is powered by motor switch cam A. By the way, how are the cams on the motor labeled? Left to right? A, B, C, etc?

I'll order a new coil, but I think there is something else, any ideas?

Thank you,


#10 6 months ago
Quoted from rufessor:

Schematics and manual suggest latch relay on game over relay as a probable cause.

Rufessor, you were right, Latch relay, Just need to find out if it is the coil or a wire/switch that is off, yet all seems good, no visible wires broken off.

When the game restarts, the game over latch relay doesn't pull the latch, but if I manually trip it, it works fine. The little coil aft of it resets that latch during game powered on.

#11 5 months ago

If the Game Over Relay is an Interlock Relay,adjust exactly the gap between the two armatures of the latch coil and the trip coil

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