500SEC Bent rotor arm after 50 miles

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OK your car shipped 15/02/1985 and the change in ignition setup dates from 09/1985 the coil and transistor box looks like the earlier type [ a coil A0001584503 or transistor box A0025452632 part no might confirm this] Couple this to wiring that's been horsed about may mean "little hands" have done some mods previously- which might explain the non running/ignition problem. Running the standard coil without the ballast resistors might explain the arcing for example- difficult to diagnose at a distance.
Ballast resistors are going to look like this if present.
Ballast+resistors_001.jpg
 
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Just had a little wire brush and a check and I’ve got the 0025452632 transistor box so it may appear somebody has taken them out and wired it as the later type?
Is it a modification that can be done if the modules are the same that it’s wired into?
In which case I can order the later coil to go with it?
I will see if I can get a coil number now...
 
But the coil is 0221118329 and is a Bosch item with a merc stamp underneath... is that the later coil?
Primary Windings 0.2 ohm and secondary windings 8.8k ohms so I would say good??
Where do we go next?...
 
But the coil is 0221118329 and is a Bosch item with a merc stamp underneath... is that the later coil?
Primary Windings 0.2 ohm and secondary windings 8.8k ohms so I would say good??
Where do we go next?...
The number is a Bosch identifier and corresponds to the old coil no A0001584503 and it has the old transistor switching unit which poses the question where are the ballast resistors?
 
Should add the 2 ballast resistors [ wire wound-high current]
0.4 ohms A0001582045
0.6 ohms A0001581345
are still available from Bosch if their absence is the problem
An explanation of the exact purpose of the ballast resistors here. altho it refers to a points based system on another model the principles are the same.
Pagoda SL Group Technical Manual :: Electrical / TransistorIgnition
 
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Thanks for the massive in depth reply!
I will lol into the voltages I’ve got when the new battery arrives and then go from there...
 
Should add the 2 ballast resistors [ wire wound-high current]
0.4 ohms A0001582045
0.6 ohms A0001581345
are still available from Bosch if their absence is the problem
An explanation of the exact purpose of the ballast resistors here. altho it refers to a points based system on another model the principles are the same.
Pagoda SL Group Technical Manual :: Electrical / TransistorIgnition

2 new resistors ordered from Mercedes for Saturday .
I will get them fitted and then update you from there.
Thanks again.
 
Also, if you’ve got any more photos of the locations and wire colours etc to make things any easier for me to identify that would be perfect
 
Found this wiring diagram on the online workshop manual I have for the 126 044 500 sec that I have and this is how mine appears to be wired. Would this be the later type after the change over?
It’s for MY 83, 84 and 85 so I would say it applies to my car?
But, there is no mention of any ballast resistors?
Any ideas?
 

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I think at the change over from 09/1985 Mercedes moved to the EZL type of ignition. Its entirely possible that Mercedes changed over to the setup you describe earlier I'm just going by Mercedes EPC parts listed under your chassis no without the benefit of a wiring diagram Sometimes interim developments don't get fully documented! I would have a look under those taped connectors to see if there are any clues there. The wrong coil just seemed to fit your distributor symptoms
 
I will call strip it all back and have a look tomorrow morning. The 2 random wires that have been crimped together (white and brown) could have been added for a component that has been retrofitted and removed years ago... there is also a ring connector on the abs bracket that’s been added to ground something at some point over the years. Could have been an alarm or anything I suppose?!
I’ve got the correct coil on it’s way tomorrow too along with a new battery and if it fixes it all then I won’t go with the ballast resistors...
 
If this helps....
On a car with points a new set of points failed as did subsequent sets (overheated and melted the plastics). The cause I subsequently found out was due to running a '6 Amp' coil which should have only been used in conjunction with a ballast resistor. The earlier points sets were more robust than the later sets and could just manage the 6A current but the newer flimsier ones wouldn't. Fitting a ballast resistor sorted it all out.
That note, was on the low tension side but doubling the LT current is obviously going to increase the HT energy possibly to the point of pushing a failure.
Mainly though - if your coil requires a ballast resistor be sure it is in the circuit for all conditions bar cranking. The current level can damage LT components - in your case if I have this correct - the electronic unit.
 
I see where your coming from and can see how one of the resistors are by passed during cranking. I will check the loom set up I’ve got tomorrow and then I can determine which way to go with it. Is there a tester in existence to measure ht voltage at the dizzy cap and then that can be cross referenced with a value from factory??
 
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This is becoming a tricky thing to get to the bottom of...
this is a picture of mine just to confuse the matter.
They both have the same 4 connections, is there any way to tell by what’s inside of it??...
 

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I see where your coming from and can see how one of the resistors are by passed during cranking.

For 'my' points set up, without a ballast resistor I should have been using a 3 Amp coil. The 6 Amp coil was from an electronic (no points) set up was fine on cranking (without the ballast resistor) as the starter motor draw pulled voltage and current levels down, but once running and getting the full quota of juice the points couldn't take the 6A current hence the need to restrict it with the ballast resistor.
With a ballast resistor permanently wired the coil can be 'starved' during cranking hence the bypass.

I will check the loom set up I’ve got tomorrow and then I can determine which way to go with it. Is there a tester in existence to measure ht voltage at the dizzy cap and then that can be cross referenced with a value from factory??

Probably there is as part of an expensive bit of garage kit. Maybe a multimeter can measure it but the HT pulses are so fleeting you would have to apply some correction factor. If measuring is possible, then with and without (ballast resistor) comparisons may give up some info.
Currents and voltages in the HT side are inversely and directly respectively linked to the turns ratio within the coil. I saw figures quoted in Grober's linked Pagoda piece.
 
RIGHT from photo
MB part no a 0025452632
Bosch 0227100042

appears to have a much more compact substitute unit now [ familar perhaps to 190 owners?]
Switch Unit, ignition system A0025452632 OE Number buy online

see this ebay link for application chart Note the previous "big metal box" acted as a heat sink but IF USING this newer substitute compact unit it would needs to be heatsink pasted to the inner wing or large metal bracket/fins
New Ignition Control MODULE For Mercedes Benz 190E 380SE 500SEC A0025452632 | eBay
 
Update time....
I have 3 red/black cables to the + side of my coil and a green and black to the - side of the coil. I also have the correct diagnostic cabling and the Tacho and and diagnostic cabling in the block on the inner wing.
It’s all factory wiring and matches the wiring diagram for 12v coil with no ballast resistors.
So, can a faulty coil burn out a rotor arm? So should I replace it even if it check out on resistance checks?
Also, the new coil is half the size so has been superseded...
I’m tempted to try to new rotor arm from Bosch and monitor it....
 

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