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1982 380sl
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Discussion Starter · #1 · (Edited)
Hello! I’m new to the forum, but have been reading everyone’s advice for some time. Glad to join, and help others with things I know about and have solved. I’m restoring a 1982 380sl that sat for years before I bought it. I’ve done massive amounts of work to it, but can’t figure out the last issue- which is, my ignition coil keeps melting! This is preceded by missing, and very rough running. I had the car running perfectly for about a day- then it started running very rough and missing while driving on the highway. Here’s what I’ve done:
Checked the coil leads to make sure they’re connected correctly.
Replaced the Ignition Control Module with a Programa unit.
Checked that with another seemingly good ICU that I have- seems to work the same.
Replaced all plug wires, cap, rotor, spark plugs with regular Bosch correct plugs. Wires are NGK blue.
Had the ignition distributor rebuilt.
Replaced the green wire.
OVP relay has been replaced.
car runs extremely rough on start up and misses and surges upon opening the throttle. It’s a real mess. Then coil melts down, oozing asphalt all over the place.
What am I missing here? Does anyone have experience with this problem?
Thanks!!
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1982 380sl
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Discussion Starter · #3 ·
Hey Ken,
Makes sense, but I understand that this car doesn’t have a ballast resistor at all, just the earlier models. I could be wrong!
 

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1974 450SL; 1961 Besasie X-3 (being restored)
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1,856 Posts
Check on the inside of the left front. There could be 2 ballast resistors, 1 blue and 1 silver. At least that's what I have on my 74 450SL. Without a ballast resistor, the coil will overheat and melt. Only other thing I could suggest is keeping the coil in a bucket of ice. :D:D
 

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1984 300D
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5,657 Posts
I did an image.google.com search for: 1982 Mercedes 380sl ignition resistors

And pics of the resistor came up. So it must be supposed to have at least one.

Don't know if needs one or 2 of them but some of those pictured had a blue bracket and others were just natural metal brackets.
 

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1984 300D
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5,657 Posts
This thread has a pic that shows what appears to be 2 resistors

 

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1974 450SL; 1961 Besasie X-3 (being restored)
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1,856 Posts
If you have ballast resistors, that's what they should look like. They are critical to your ignition system.
 

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1982 380sl
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18 Posts
Discussion Starter · #9 ·
What’s the alternator voltage at high rpm?
I will check it. After I put another coil in of course. Are you thinking voltage regulator?
Thanks
Check on the inside of the left front. There could be 2 ballast resistors, 1 blue and 1 silver. At least that's what I have on my 74 450SL. Without a ballast resistor, the coil will overheat and melt. Only other thing I could suggest is keeping the coil in a bucket of ice. :D:D
Maybe I’ll try the ice, or, at least rig it to the A/C compressor 😉
 

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1982 380sl
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18 Posts
Discussion Starter · #10 ·
Thanks for all the ideas, but, I swear, there are no ballast resistors on this car! I even bought one several months ago only to discover that 82 380 does not use one. It has the TSZ 8 z ignition with no resistors- see below.
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1996 SL500, former 1986 560SL
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271 Posts
Does yours have the "green information label on the original coil and switching unit" mentioned in that document?
What is that document and where is it from?
It refers to "National versions"... what does that mean?
 

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1982 380sl
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Discussion Starter · #12 ·
Does yours have the "green information label on the original coil and switching unit" mentioned in that document?
What is that document and where is it from?
It refers to "National versions"... what does that mean?
Hey Ken,
Yes, I have the green label- this is the third coil I’ve bought (Bosch, from Autohaus AZ). The pic is from the factory service manual. I am starting to suspect the voltage regulator…
 

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1974 450SL; 1961 Besasie X-3 (being restored)
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In simple terms, the ballast resistor limits the amperage, or current flow, through the coil while the engine is running, thereby extending the life of the coil and breaker points. You have a breakerless ignition. The only thing I see in this diagram that could be a problem is your Ignition Control Module. The attached diagram is for an 84 380. I don't see a resistor of any kind. The Voltage Regulator is part of the charging system. I'd look at the ICM first. That's where your amperage to the coil is coming from. On this diagram, there's a pretty heavy wire coming from the diagnostic socket--if you have one.
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1982 380sl
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Discussion Starter · #17 ·
Rcrmonte3,
Thanks- I agree there’s not much that can cause it except the ICU- is it possible I’ve had 2 bad ones in a row from Programa, and a third bad one from the junk yard? Any way to test the units? I tried the solid state one from Beru- car wouldn’t even start, so I sent it back. ICU gets extremely hot, BTW- not sure what would cause that other than too much voltage?
 

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Outstanding Contributor , Bob's Your Uncle!
83 280 SL- 5 speed-The PIG
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Sumthin sumthin weird going on.

Bad multiple ICMs and coils?

What kind of voltage would an alternator need to produce for THAT?

And wouldn't the OVP relay protect it?

Spit balling...I'm not familiar with the 380
 

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1982 380sl
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Discussion Starter · #19 ·
Sumthin sumthin weird going on.

Bad multiple ICMs and coils?

What kind of voltage would an alternator need to produce for THAT?

And wouldn't the OVP relay protect it?

Spit balling...I'm not familiar with the 380
nobby,
No doubt! I’m at a loss. I did just replace the voltage regulator since I had a spare one sitting around. Thought it might be the wrong one, but both part #’s are interchangeable according to Transpo website. Anyone have bad luck with this brand of regulator? I went ahead and sent back the ICM too in case it’s fried again. Smells fried….
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1974 450SL; 1961 Besasie X-3 (being restored)
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Rcrmonte3,
Thanks- I agree there’s not much that can cause it except the ICU- is it possible I’ve had 2 bad ones in a row from Programa, and a third bad one from the junk yard? Any way to test the units? I tried the solid state one from Beru- car wouldn’t even start, so I sent it back. ICU gets extremely hot, BTW- not sure what would cause that other than too much voltage?
Will, if I could, I'd go further, but I'm more familiar with the earlier, virtually non-computer, ignitions. The only computer I have in my car is the ECM, which controls the D-Jet. If your ICM is getting hot, there's either something wrong with it or, for some reason, it's getting way too much amperage. The only thing I can recommend is tracing every wire that goes to the ICM. There just may be a bad connection that is causing a short somewhere. I agree with Nobby. Multiple bad coils and ICMs would be weird. Good luck. Sorry I can't help more. If the ICM smells fried, it probably is, which to me would mean there's too much amperage/voltage going through it. Where is that extra coming from? I don't know. All I can say is it involves the ICM and the power going thru it.
 
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