I have a 1976 Williams Grand Prix. I am trying to get this thing working 100%. It seems like ever time I get something fixed there is other stuff wrong. The problem I am trying to figure out right now is when I start a one player game everything resets and ball kicks to shooter lane. If i start scoring 10,000 or 1,000 it will advance the ball to ball 2 if I keep scoring it advances to ball 3 keep playing then game over. This is with the ball never draining. So scoring is making ball advance. If i manually actuate the 10, 100, 1000, or 1000 relays it does not make the ball advance. I have also noticed every time I push the start button i get a pop like you get with free game and the credit wheel does not go down. There is other stuff if in say 4 player game like not advancing past 2nd player 1st ball. I start a 4 player game I start playing 1st ball then when it drains it goes to 2nd player 1st ball then i play that ball and it drains it kicks back out and stays on 2nd player 1st ball forever. I don't know if this could all be contributed to same thing or if it is multiple issues. I would really appreciate any ideas for me to check. Thanks

The outhole switch is good. I hit playfield and could not make it do it. I also put paper between the outhole switch contacts and as soon as I score 10,000 it advances to next ball. When i score the 10,000 the ball index relay and the outhole relay pull in. Thanks

All Jones plugs are in right. I have cleaned the male and female parts of all of them. If i activate the 10, 100, 1000 or 10000 point relays by finger it does not make the ball advance. I can solder decently. Thanks

When i did as you said in your post 6 the 1k score moves and the 10k score moves. Neither one of them makes the ball count advance. I have noticed after reading some stuff that the bonus on the left and right drop out at startup and then go back up to 5000 but then the right side goes back down to 0 no light lite. I have also noticed that everything that triggers the ball advance has bonus associated with it. Spinners increase bonus. The 2 outlanes increase bonus. That seems to be the only thing that causes the ball advance. If i score the inner lane 10,000 on both sides it does not advance ball. So could it be a bonus unit issue? Thanks

Sorry about that the 1k moved with the 1k relay coil test and the 10k moved with the 10k relay coil test. When i activate the left advance relay the ball count does not advance. When i activate the right advance relay the ball count advances from 1 to 2. The right bonus arrow is lite on playfield. Also I noticed when I press the left outlane switch which scores 10,000 and suppose to advance left bonus both left and right advance relays pull in. when I press the right outlane switch which scores 10,000 and suppose to advance right bonus both left and right advance relays pull in. I did not know if both advance relays are suppose to pull in anytime a bonus switch is activated. Thanks

I figured out there where 3 wires that someone soldered to the wrong lugs on the right bonus unit. It does not advance ball anymore just from scoring like it was. I have noticed that when the bonus resets to 0 the left bonus pops up to 5000 like it should. The right bonus bumps up to 5000 and then back to 0. Also when I trigger a switch that is suppose to advance left bonus it advances both left and right bonus. When i trigger a switch that is suppose to advance right bonus it advances right and left bonus. Any ideas? Thanks

If you hit the left bonus score switch both left bonus relay and right bonus relay pull in. If you hit the right bonus score switch both left bonus relay and right bonus relay pull in.
Both pull in.

I have looked and looked and can not figure out what is making both the left and right bonus to advance every time a bonus switch is hit. HowardR, I see on the schematics where it looks like the change relay could maybe cause this issue. I have put paper between each switch on the change relay with no change. Can you give me some ideas of what I might look for as far as the left and right relays being shorted together. Thanks

I found this tonight. I got a feeling this has got to be my issue. I wanted to post this link so if anyone ran across this post they could go to hopefully the solution. Who would have thought stand up targets. https://pinside.com/pinball/forum/topic/grand-prix-lr-bonus-advance-always-pulse-simultaneously
I will report back when I can look at my machine. Have Thanksgiving stuff this weekend. Thanks for everyone's help so far. Happy Thanksgiving to everyone

I looked at my machine and the stand up switches behind the rubber rings is what was causing both bonuses to activate at the same time. I am going to mark this resolved and start a new thread on my latest issues. Thanks to all.