ignition control module

[ewenjo]

Need advice ..(as usual)

My 380SL will not start. There is no spark at the plugs. I am reading the forum and researching the electrical schematics. It seems that most point to the Ignition Control Module. Looking into the price for the replacement module is somewhat staggering.... $250 -700. Further research indicated that there is a updated replacement unit made by Hueco. The module is smaller, different shape, and is said to be a "modern" replacement and is priced at less than $60.

Does anyone have any experience with this Hueco product? And if it indeed is a replacement, is there anything else that should be changed upon installaion? I have read that the ignition coil should also be changed when installing a new ICM.... is that correct?

Thanks for any insight

[ewenjo]

Upon reading the Forum, I noticed that the "Crankshaft Position Sensor" could be a problem with starting> Does the 380SL have this and if so where would it be located and can it be tested?

Thanks

[Deltacom]

It seems your issues with ignition problems emanates from your earlier issues with the AC. The first port of call would be to turn the ignition on and test voltage at the coil (the + and – poles). If there is voltage then test the primary and secondary winding on the coil (disconnected from wires) and ascertain the correct resistances for your coil to establish whether your coil is faulty. Then you can proceed with testing the ICU before embarking on expensive replacements. Just FYI these ICU and coil and the suitable for your model. I have them on my car to replace earlier ballast resistors coil and ICU and have been performing beautifully for the last 7 years. BTW, the cranckshaft position sensor play no part on ignition process. It is only for diagnostics.

[ewenjo]

Thanks for the reply Deltacom

I have checked that there is power to the coil. I have not checked the resistance. In your pics, are the ohm readings correct. I don't know what the proper resistance values should be.

Also I noticed that you have a different coil. I did not see that one when searching for parts. So my question is, if I do replace the ICU with the Huco version, do I need to get that particular type of coil replacement.

Thanks for the great info and pics

John

[Deltacom]

John, for your model (82 380SL I believe) the coil should be Bosch 0221118329 and the resistances on primary winding should read 0.3 - 0.6 Ohms and secondary 6 – 15 Kohm (+- 0.3 and 1 Kohms respectively).

You do not need to replace the coil (if it is working to specs) if you replace the ICU. The replacement of the coil refers to previous versions that used external ballast resistors. Your coil has inbuilt resistors. The coil I replaced with the one on the pic above in conjunction with the ICU was to obtain higher ignition and because my model used the external ballast resistors and my original coil was not compatible with the Huco ICU replacement. The Huco is a straight replacement for your ICU with your existing coil.

[ewenjo]

Latest on the progress:

I checked the ignition coil and it seems to be within specs except for the voltage reading:

Primary Coil Resistance: 0.7 ohms

Secondary Coil Resistance: 10K ohms

However, Voltage at the coil was questionable. With power feed connected (+ side), voltage was 10.7 volts to ground (?). When I disconnected the wire and read directly it read 12.3 volts to ground.
A drop of 1.6 volts doesn't seem correct.

I disconnected the 4 pin connector at the Ignition Control Unit (ICU) and took a voltage reading on pin 15 (power in) and ground, and it was 12.3 V. When I reconnected the ICU , sure enough, the voltage was 10.7V. QUESTION: IS THIS DROP NORMAL AT THE ICU?

I removed the ICU (pictures attached) and checked resistance at pin connections.

Connector Pin Descriptions:
pin 15 power in
pin 16 ignition
pin 31 ground
pin TD RPM output

Ohm Readings:
pin 15 to 31 infinite no continuity
pin 16 to 31 continuity
pin TD to 31 infinite no continuity

Since I don't know really how to check if the ICU is defective, I am asking you experts for an opinion. Thanks for any insight.

[david s poole]

you can take that ignition control module apart and inside you will see a ballast resistor to one side that burns up and needs replacing.i have fixed several that way.you cannot leave the ignition on with these units as they will get hot and burn up the mentioned resistor.

[ewenjo]

Thank you Deltacom and David Poole

I replaced the ICU with the Huco unit and also replaced the ignition coil after doing the diagnostic check according to my MB CD. The voltage reading was extremely high between #1 and #15 terminal (7.2V) which suggested the ICU was defective.

After the replacement the car started right up. SO now back to the initial ACCIII Blower problem. (Ref earlier post ACCIII Problems)

The curiousity still nags at me, as to why the ignition problem started after I "wiggled" the key to see if there was an effect on the blower operation. Coincidence??

David, where can I get the ballast for the initial ICU

Thanks