What happens when you push the coil by hand with the PF up? You should be able to see the entire action happen? Is there a guide out of alignment? Check the wires on the coil. Make sure they are completely soldered on. A wire with bad or little solder hanging loose would prevent the coil from firing full power.

I had the same problem. A friend fixed it by bending the metal peice that the coil fires from. The door has worked fine for two years and counting.

Definitely the wires.

Stern issued a bulletin on this issue early on and recommended upgrading the coil to the next size up. I don't know if later year runs had a stronger coil or not. I had a pop bumper locked on and it fried before I could get the machine shut down, so I ordered the stronger coil, swapped it out with stock one in the garage and put that one in my pop bumper as it was the same size as the fried one.

You could very well need a new or stronger coil or a re-adjustment of the plunger angle. But maybe start by looking at simpler fixes first. Try giving the plunger assembly and door hinge a good cleaning. I found that worked for me (mine's a '07 build).

A few possibilities:

1. The bracket that holds the coil could be a little bent--if so, just bend it back.

2. Existing coil could just need a new sleeve/plunger cleaning.

3. Or just upgrade to a Stern 24-940 coil (as the service bulletin recommends).

Im going to hijack this thread as im having the same problem. i have replaced coil, diode, sleeve, and adjusted alignment so the plunger avoids missing the metal cross bar. garage works fine for a few times per game and then slowly starts sagging so as not to allow any balls passage. when i lift up playfield my coil is hot to the touch... My question is, should this coil be getting that hot? ..and any other suggestions.? maybe torturing the metal bracket more so it has even more avoidance away from the metal cross bar?

Here you go...you can thank me later.
http://doors.networx.com/c.Simpson-Garage-Doors/

Or should that nylon plunger hit the cross bar...?

Stick a little foam pad (like the one behind a target) on the inside of the door where the tip hits it. Low cost, no more problems.

Coils will get hot, but sounds like it could just be a bad coil. Typically the amount of usage it gets shouldn't get that much weaker as the game goes on.

I had the same problem. Turns out there was a stern released service bulletin for the game about this. The coil in several stock games was too weak and an upgraded coil was recommended. I swapped the coil and it's been great ever since. I think the service bulletin recommends a 24-940 coil.

One more vote for upgrading the coil. Once I did that, no more problems.

I have the same problem , i will change the coil to see if it solve the problem , it seem to be tired and solved my problem when i had i problem with up kicker coil .

Uhhhh, 24-940 was mentioned more than once in this very thread!

I messed with this for a year (adjusting parts, foam pads) and it worked on and off. Upgraded the coil and it was 100% perfect. This is the fix.

help!
A buddy and I tried adjusting the parts, foam pads, a new stronger 24-940 coil and still having the exact same issues.
It stars up fine but then it "tires", especially during multiball.
Any insights would be tremendously appreciated!

Replace the plastic plunger pokey thing? I could see it wearing to the point it doesn't work well. I had to reshape mine by grinding it. I don't think i could get away with that a 2nd time. It will likely need replaced down the road.

I'm still having the issue with the garage door. It only happens after about an hour or so playing. Or if a ball hits it while it's opening. I'm not sure if the plastic thing would be the issue, since it opens 100% every time for the first hour or so.

I looked very closely at my pokey thing and it's in pretty good shape. game is HUO.
so i really don't know. at a complete loss on this one. even my friend who's a tech for an operator can't figure it out.
:-/

Bad/failing solenoid transistor? Got another board to throw in there?

hmm... haven't tried that.
i'll ask around if i can find another board to try. thanks

I just placed an order to try out a new transistor. In the manual, it says that it's a Tip122 Transistor. Q20 on the board. They were cheap, so it doesn't hurt to try. Sounds to me like that might be the issue though since the garage door opens fine for the first hour or so. I'll let ya know if that solves it.

That's what I'm thinking, failing acter heating up.

I installed the new transistor last night, but only played a few games since it was late, The door was working fine, but i don't think i was playing enough for the door to start sagging. I'm going to play a lot today, i need to wait a bit though, it's not even 8am yet. I'll post later on today to let you guys know if it solved the problem.

Edit: I just tested it. I played for about 1.5 hours straight. Had a few good games. Had couch and I&S multiball going many times, I also reached the Mystery Spot. The garage door was solid the entire time, it never sagged once, I haven't seen the garage door be that stable since buying the machine. So happy to have fixed the issue

Glad to hear that resolved it for you!

For anyone who does a search on this issue something I found that hasn't been mentioned.. If the door opens but after a while it drops a bit..

Change the coil to the stronger recommended one. Verify solder joints are solid. Make sure everything is aligned (bracket isn't bent)and the plunger is touching the door but NOT holding it open at all (add a rubber shooter tip to the plunger end OR double sided tape to the rubber stopper on the mech to take up the gap. Remember the door has to have just enough play for the switch inside to activate when the door is hit.

Lastly (and this was my issue after verifying and upgrading everything)

Make sure there is no compression washer OR compression spring on the plunger. It's NOT needed and apparently some earlier models have it. Remove them both.

If none of these fix your issue, replace the TIP122 at Q20 with a new one (OR TIP 102) as the transistor may be weak.

I like the shooter rod rubber tip idea... My plastic plunger is pretty well worn, so i will try that.

Mine had the weaker solenoid installed. Instead of replacing it, i took off the number of tuns to match the recommended replacement.

I had to work on my TSPP again (TSPP has been my problem child lately... this time ANOTHER flipper return spring broke) so i tried the shooter rod rubber tip on my game since after repeated play (hours on end literally) the garage door would have trouble staying up. For the me this didnt work. The rubber tip made the shaft bind at some point and the door would always stay up unless i forced it down. I ended up taking some heat shrink insulation and forming it around the tip to widen it. So far this seems to be working really well. I think this compensates for the fact my tip end had gotten worn to the point it was smaller.

***redacted**** I'm an idiot, apparently. I got it figured out.

Ok I'm going to try here too.....My garage door wasn't really working well. I changed out the solenoid to the new 26-940 reccomended stern upgrade. Well, I was blowing a fuse so I figured out the new coil is ground wires on the other side so I moved it and resoldered. Now it is locking on at boot and never dropping. Well I decided to reverse all I had done and put on the old solenoid. Well that changed nothing it still locks on

Anyone have any idea what I could do?

Thanks for any help you can give

Sounds like you might have fried the transistor by wiring it backwards and it's now shorted? Just a guess, but I'd test the transistor that corresponds to the garage coil. There's videos on YouTube on how to test whitestar transistors on LOTR for example and the TSPP manual can tell you which Q # is the one. Pulling driver board is easy on TSPP

Yep you blew the transistor. It really is easy to fix if you have basic soldering skill and take your time.

Marked