So my AC/DC is a couple months old now and it seems like the auto-plunger is getting weak - it fails to make it to the saucer fairly often. When brand new, it never missed. Then after a month or so it would miss once in a great while. Now it is getting to where maybe only 50% of the ball launches make it to the saucer.

Anybody else seen this problem and if so, what did you do to fix it?

Thanks Lloyd, but I have not tried to troubleshoot this yet as it is alien to me! The auto-plunger uses a fork type mechanism to launch the ball. This game has a traditional pull back plunger along with an auto-plunger.

So, since I have no experience with this type of mechanism, 1st I searched and found nothing and then I posted asking if anyone else has expereince with it.

Thanks Lloyd - I will check the fork to make sure it is peened together tight. It does look like something is out of whack because the manual plunger is not centered between the forks. I t looks like both mechanisms are off. The forks are too far to the left and the manual plunger is too far to the right. I will have to mess around with it some more to figure out if there is slop to allow adjustment or if something needs to be bent on the fork mechanism.

I guess I did not know what term/s to search for cause my search came up empty.

Yep - that is how mine is. It may work OK for an entire game - then it misses 6 in a row! Really annoying when you are trying to make the jukebox shot and you drain the ball and then think that's OK, cause the autoplunger is going to make it for me.... Then it misses. And to make the worst, I have intentionally let it drain to give it another shot at the Jukebox and it misses again, wasting all my precious ball save time in the process.

Then again, it is AC/DC so you know it is as mean as hell!!

I fixed the problem tonight so I thought I would report back in case it might help others who have the same problem.

So I did a bunch of checking into this problem. Nothing was loose, the plunger fork was riveted tight, the coil and sleeve were all fine. There really is no adjustment to align the fork so it can't be out of alignment.

The problem turned out to be that the left "tine" of the fork was bent away from the other tine. That was causing the right side of the fork to hit the ball first and making the plunge unbalanced. I carefully bent the tine back into alignment and now the autoplunger shoots smoothly and strong.

This does leave some unanswered questions: What caused the fork to bend? Does that just happen over time? Will I have to bend this back again after more use? Will the fork break off if I keep bending it? Is it a defective part?

Has anyone else seen this fork bending problem?

Ha! There is no slight of hand with this fork bending...

Mine started acting poorly again. It got so bad, it was only making the launch to the jukebox about 1 in 4 times. And sometimes it was so bad the ball did not make it all the way up the launch ramp so it had to try again..

I fixed it right this time! Tracelifter was right on target with the slop on the fork pivot. Mine had at least 1/8" of play at the fork tips. I decided the plastic bushings are the problem. I made a new single piece bushing out of brass and now my fork has almost zero play and the shooter is making the shot to the jukebox every time.

Here are some pictures of the bushing in case anyone else wants to build one. I used 3/8" brass rod stock. I turned the narrow section down to 0.318" and 7/16" length. I left 1/16" shoulder and reamed the center bore to 0.249". It is a snug fit into the U bracket.

ACDC_Autoplunger_Bushing_9539.jpg ACDC_Autoplunger_Bushing_9541.jpg ACDC_Autoplunger_Bushing_9542.jpg

I would not mind making some of these for sale, but it takes me a long time to machine them - my lathe is old school - not CNC....

Not sure I could pay for my time and still sell them at a cost that would be bearable.

Those plastic bushings are junk! I am certainly not a Stern basher since I love my AC/DC, but I could not help thinking that Bally/Williams would have used a brass bushing there and I would not be making this thing myself....

I just played a couple games and not a single auto plunger shot missed - which is awesome!! I might go ahead and build some of these since it seems like there is a lot of interest in them. It would probably be prudent to wait a little while to make sure the brass stock I used is going to hold up. I used C360 alloy brass rod.

If I am going to make a batch of these, I could get some thick walled brass tube stock and it would make the machining job easier since it saves me the center boring step - just have to run the 0.249" reamer through to accurately size the bore. I found a source for 0.375" OD / 0.245" ID tube which would be perfect.

One concern I have is how accurate are the brackets from Stern. I only have a sample of one - which is no sample at all really. If I machine the bushings exactly the same size as mine - are they going to fit everybody else's brackets?

That is a valid concern. There are many different alloys of brass each with different wear properties. I have a No Fear game myself with many thousands of games on it and the long flipper bushing has been holding up well. I did lubricate it with white lithium grease though. Nylon is self lubricating - brass is not. I did lube this auto plunger bushing with a small dab of white lithium grease also. I will have to see how it holds up.

The main problem with the original bushings on AC/DC is that they are split and do not fit to a close tolerance even when brand new. My auto plunge fork has had lots of wiggle since day one. If the brass does not hold up - I could machine a tight tolerance nylon bushing that would be much better than the two split bushings.

The problem with using nylon for this application is the wall thickness of the bushing ends up being too thin. When you try to machine thin nylon, it flexes and you end up with inaccurate cuts.

Now if you want to spend a fortune and set up a mold to make these, you can make the wall as thin as you want.

To use a proper sized nylon bushing (meaning one that can be machined accurately), you would need to drill out the holes in the U bracket to allow a larger OD on the bushing. 0.375" would probably do it, but that does not leave much metal in the bracket. And it certainly eliminates the plug and play feature of the brass bushing.

I still think the brass bushing is the way to go. I really don't expect to see much wear here since it is only rotating a few degrees.

I have not decided to make any of these for sale yet. Since there was a concern about wear on the brass, I have just been playing my AC/DC to see how well it holds up. I have a couple hundred games on it since putting in the brass bushing and so far it is holding up great! Out of all those games, the auto-plunger has only missed the juke box maybe a dozen times, so the success rate is fantastic!

As far as stock sized tubing, you need something with a flange on one side, so tubing is not going to be the answer. You can try new OEM plastic ones, but I think they are sloppy from the beginning, so they may improve your shot success, but still leave plenty of misses which I found very annoying on my AC/DC.

And turning off the auto-plunger sounds terrible - it would pretty much ruin multiball if you had to manually keep plunging balls while still playing the ones on the field...

I don't have any experience with stock size bushings but I doubt you will find one that is the right size. The dimensions are critical if you are going to get the play out of the auto-plunger. 1/4" inside should not be a problem but 0.318" outside does not equate to a standard fractional size. 5/16" would be 0.3125" which would be sloppy in the hole on the plunger bracket. You could step up to 3/8" (0.375") and then drill out the hole in the bracket, but I did not want to modify the stock part and potentially weaken it since a 3/8" hole would not leave a lot of material behind. The 1/16" flange width and 7/16" turned length are also very critical or you won't be able to get the circlip back on. There is no adjustment for that other than go slightly undersize and use very thin washers.

I think your best bet is to find a machinist that does small jobs and have him build a bushing ( or bushings) to the specs I posted.