Thanks Turbo.

Yes, you are thinking on very similar lines to me. The low voltage theory doesn't hold water to me.

Alternator spikes are one theory of mine, hence the alternator change.

My impression also is that the destruction takes place at start-up. I cannot be 100% sure but I feel I heard the engine fire before the EZL died and then nothing.

And I really do not support the idea of EZLs needing any further cooling than good heatsink paste to the bulkhead. I have never felt my EZL get any hotter than "tepid", even on a hot day. Certainly nothing like a hot as a hard working power amplifier driving some naughty B&W speakers.

And also on heat, these cars were supplied to Saudi where things get seriously hot. Did all the EZLs fail?

Like you, I am now hoping for the best. I do not know if my measures will bring about success or failure as the car still starts - and it did before, for a few months!!

Oh well.

RayH

When mine died I did not have any stuttering at all. Just cranked. As far as thermal stuff goes, I agree, it doesn't get that hot. What I'm concerned about is the cycling change in temperature leading to a breakdown of something in the ezl-be a solder joint, bond wire or solid state junction. Mine was dead when I went to start the car, i assume it died when the ezl cooled off, something in its circuitry just went open. But then that kills my dying alternator theory (and my alternator WAS dying, its been replaced right before the ezl died) because you'd expect it to die suddenly while running. I did try experiments to get it to work again but wasn't successful. I tried freezing it and starting the car as well as getting it hot but never even had a stumble. I need to open up that one I have and see if I can find if any parts of the board are still working to get some insight into why they die.



I'm also wondering...Are Siemens ones more likely to fail? both my working one and spare are bosches.

More food for thought.

My impression is that mine have died on startup - did I detect a bit of firing before death? Can't be sure.

I have NEVER had any running issues before death. This car has always been a prompt starter and a smooth runner. Even at 400+ K Kms, it performs like a new car until sudden death.

This problem arose after I replaced plugs, wires and coil. And the genuine MB cap, rotor and shield were all only a year or two old. Did I screw up something? I've maintained the ignition system in this thing for 20+ years so it's unlikely but possible. But what? Are these things really so fragile? Difficult to believe.

The ones that have failed for me are: 2 x Bosch A0105459532 and 1 x Siemens A0125452132.

The one that's working fine right now (or was yesterday in 35C heat!!!) is a Siemens A0105459632. So, I cannot say that Siemens or Bosch are more or less reliable.

More as it happens.

RayH

IS THIS A CLUE?

To recap; 3 EZLs blown in the past year despite almost new HT components, including coil.

I had the impression that death was at startup as I was vaguely conscious of a brief "fire" before death. We concluded that, possibly, some electrical surge was blowing these EZLs.

So, the latest measures included checking and cleaning all accessible earth/ground connections. And then a new (rebuilt by Bosch in Spain) starter motor and alternator have been installed.

Of course, I know not if I've solved it until the car does not fail to start for some time; a year, two years?

But, I have noticed one change.

Before, when closing the electric windows (front ones on a coupé - significant current), the revs would drop slightly and then recover.

After our measures and the new starter and alternator, when shutting the windows, absolute stability. No revs drop. Nothing.

I can't get too optimistic yet as the car was always performing like new - better by far than when I took delivery when it was 6 years old with 130k Kms (80k miles) on the clock.

What do we all think about that?

As always, best to all and keep those comments coming in.

RayH

If it were me I'd take one of the old units apart and look for the specific issue that killed it. It's also odd to me it wants non-resistor plugs since those make noise and electronics generally don't like that. Some think one or the other affects the ign due to current draw but that's ignorant. I'd put resistor plugs in but up to you. I'd also be wary of the coil because new does not mean good. I think I'd rather have an old coil that has proven it works than a new one.
If the coil shorts internally it can cause excessive current draw, which may only appear when hot btw. If your transistor(s) in your module have blown I'd just install some external ones.
Back when I was a kid I got tired of points altering my dwell and timing as they burned (and the cost of new points) so I put a pair transistors between the points and coil, problem solved. Transistors make heat so if moved out of the box then your other components will be cooler.
Or just lose the box and put in an aftermarket setup or home made setup. I see your box has a vac line, so if this is how it controls vac advance, and you still want vac adv, then it just got more complicated. Not impossible, just more complicated. I mention these options if that module is expensive and/or hard to find.

25 August 2020

Not exactly an update but a status report.

After 3 EZL burns we've:

> Checked and cleaned all earth connections.
> Installed a new alternator (90 amp).
> Installed a new starter motor.

Has anything changed? No, the car is running like new but it was before the first EZL failures.

To recap, I said that my impression was that the EZL death was on start up. That was just an impression; there is no evidence of this.

EZL death may be happening on shut down. Does this give us any other clue? Not that I can see.

>>> One small difference is that, if the car is idling and one raises the electric windows, the rev counter doesn't move. Before installing the new parts, the revs would drop noticeably and recover.

Any clue here?

To my mind it must just be the grater capacity of the new alternator.

As always, any and all comments welcomed.

Best to all.

RayH

A thought came to me today: Relays can pump a high voltage spike into the cars system when they're turned off. A relay is just a mechanical switch but it uses a coil to create a magnetic field to actuate said switch. When you turn it off it's similar to how the ing coil works; it generates a high voltage spike. Note I said similar, not just like. This is not good for delicate electronics and while I've never had an issue, it can be one. This may explain why your ign box dies on shutdown because you just killed power to some relay(s) that pumped a voltage spike into the system.
So, if you have relays that weren't in there when the car was new, like maybe to control an elec fan or who knows what, it/they may be the cause. It may be that when the ign is on the system as a whole (battery included) can absorb the spike so no harm. If say you hooked said relay to the ignition power circuit so it only works when that's on, now when you turn the key off you just excluded the battery and everything else leaving the ign box alone in a circuit making a voltage spike. A spike looking for a place to go in an isolated system is like a drunk in a bar looking for a fight and everyone clears the room except a 98lb weakling (ign box), which gets punched right in the face. Corny analogy but it was entertaining for me.
Not saying this is it, but certainly a possibility and seems very reasonable to me. So if you have said relays you may want to put diodes across the coil pins of the relays(s). I suggest a Schottky diode because they're faster and will work better than a silicone diode at catching spikes. Just be sure it's rated for a couple hundred volts which I think most are? Then solder it backwards across the coil pins. If soldered fwd you'll just smoke it and/or blow a fuse. The point is the coils voltage spike is reverse polarity so when it fires off the diode is right there acting as a short.
Since we're on the subject, it's possible an oem relay is causing it too. Maybe the spike is getting to the ign when normally it doesn't. I suppose if an ign switch has more than one contact inside it could break the relay circuit a microsecond before the ign? Or maybe whatever oem relay(s) are on a circuit that has a single diode they share but either the diode died or the circuit was moved to that shared by the ign box, or the ign box circuit moved to the relay circuit. Like maybe one or the other circuit stopped working so someone moved it to another spot. Just guessing, but a thought.

Another thought is to simply make or buy a filter for the power to the ign box so it's safe no matter what kind of weird crap is going on elsewhere. Ironically, the filter uses a coil. Basically fight fire with fire. Other weird crap could be something like the coil in the starter is kicking back which would cause it to die the moment you let off the starter which you described. As in maybe the circuit for the starter is connected to the ign, or is somehow bleeding into it. A long shot theory here but if say the spikes only place to go is in the ign switch, which is normally cut off when you release the key. With wear it makes copper and carbon dust, and the key likely has grease for said contacts. Copper and carbon in grease make it conductive enough that a spike just may blaze right through it so the spike that had nowhere to go, now does. Long shot but who knows. So do you try to find whatever gremlin that may be anywhere, or just put a filter on the thing? Or at the very least put a diode on the leads to the ign.

And as mentioned earlier, I'd use external transistors to actuate the ign coil. Option A; have the internal transistor(s) power the external one(s). If you check a now bad ign box and the output transistor(s) are not working the then you could use the pos (or neg) that drives them to instead drive the new external one(s) and save the box. I'd use two transistors because it's easier on the transistor since a coil is a heavy load, at least the coils I've used. Plus if one fails for whatever random reason you're still good to go. I'd assume the factory used two for the same reason?

What you mentioned about the power windows and rpm is a battery thing, so my guess is the new alt is simply charging the batt properly. When the batt is weak it relies more on the alt which is why you see a drop in rpm. If the batt is good it powers the windows with much less voltage drop, it's the voltage drop that triggers the alt to kick in, and how by how much, so the less power the batt had, either old and weak or just low, the more the alt generates and the more it generates the more of a load on the engine.

I'm not a fan of modifying standard parts. The car's original and I intend to keep it that way.

So, my quest is to find out the cause of these failures. With the new alternator and starter motor all is well but I shall not know until the current EZL doesn't fail. Ridiculous, really, as it's difficult to make a judgement on something that hasn't happened!

Other restoration work continues and all is, for the moment, well.

Watch this space.

Thanks for your continued interest.

RayH

m104 motor EZL----6 cyl (300) 24 valve

Old JC has done little as saviour of my EZLs.

Is the solution for me to go to church more often?

R

hey, going to church is always a good plan! God fixes my cars all the time but my w124 6 cyls have not been able to get an appointment for some reason......reminds me of the old joke where the guy is asking God "why me?" and this voice comes down from the heavens "well....there's just something about you the pisses me off!"

God is very busy now trying to keep safe and healthy all of the COVID patients and the people and animals suffering from the fires in the west coast. God always helps but sometimes in ways we don’t understand.

Amen amen