Hi Pynke....
I don't know that I'll be able to help you a lot because I'm still coming up to speed with my system. But I think I might be able to give you a few hints. But first, I think you need the history a bit. It sounds like you had a running machine and then you did something (why, what, etc), and now the machine doesn't work. If you can fill in some of those blanks, that might be useful.
Now for a few hints and suggestions. First, Mitsubishi still has some folks that are very knowledgeable on the M3. I am a newer DM4400M owner and I called Mitsu here in the States and they had folks that knew "stuff", including Dyna specific, right from memory. I was impressed. My biggest issue then is that I didn't know squat about the M3, but it sounds like you had your 4500 running for some time before you did "something" and now it doesn't work. The point is that Mitsubishi might be able to give you directions that make more sense than when they gave neophyte little me information.
First off, there is a battery backup in the M3. The original batter (200mAh, as I recall) would give you about 2 months of backup time *when it was new*. If you haven't changed your battery, or it wasn't charged, or you went over that time, you probably lost your memory. This should be fairly easy to fix. There is information on this forum on how to do that or I could dig it up and send it to you. I haven't actually used those processes because I've been good about battery charges (I actually changed mine to a 1200mAh guy... we can talk about that too). Inside the control, there is a tool change macro (9000, as I recall, on my machine.... probably the same on yours) that may have been lost. In fact, there were two different macros over time, so it is possible you have one or the other. These are covered in the manuals... Do you have manuals? You'll need to restore that macro, at a minimum, if you have lost your memory. You hopefully also backed up your parameters or you'll be doing a little hand editing.
I think that the PLC will be fine. As best as I've been able to ascertain, the PLC is actually written into EPROM. Now, it *is* possible that your EPROMs have gotten corrupted. That would really be bad because I don't know where you can get new ones. I've been meaning to pull mine and copy them for that "just in case" scenario, but I'm afraid I may not have backed everything up yet. I'm still pretty green with this machine.
One thing you said that doesn't make a lot of sense to me... I know for a fact that the tool changer is fairly independent on my DM4400M. I'm assuming the same is true for your setup. You can post/send me a photo of the electrical cabinet to confirm, but there should be a large board in the middle. That is the main interface board with all of the switches, etc. Mounted to that is a card cage that has two boards in it. Those are the boards that control the tool changer. one of the boards has an LED on it that indicates the current tool number. Anyhow, the point is that the tool changer works almost like an indexer. The control sends a command and then the tool changer subsystem has a certain amount of time to unload, rotate, and reload the new tool, then confirm with the M3 that this has occurred. The m3 is *not* doing all of those operations itself in PLC. This is good and bad. It may mean that your M3 is fine but you have some funnies (or not so funny!) things going on in the subsystem only. For instance, you said that the changer continues to rotate. That is strange... It sounds like the hall effect sensor isn't feeding back into the subsystem?
Anyhow, maybe you can send along a bit more information and we can sort it all out.
Alan