W211 AMG Discuss the W211 AMG's such as the E55 and the E63

E55: s/c magnet problem

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Old Jun 22, 2021 | 02:00 PM
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W211 E55 AMG
E55: s/c magnet problem

Hi all!

I hope you can help me with the following issue. Last week, my mechanic placed a new 77mm s/c pulley and flashed the ecu with an updated RaceIQ tune. Also, he checked the pump, the vacuum hoses and the relais.

when test driving, the s/c did not spin. SDS mentioned a problem with the s/c magnet. However, when you put 12V on the magnet, it engages with a clunk. Can this be the problem with the diode in the connector of the magnet?

Any of you that can help me out?
thanks in advance!

KR Martijn
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Old Jun 22, 2021 | 05:22 PM
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Do you have the code number from SDS relating to the magnet? That will tell us what to look at next. There was another thread somewhat recently about an SC magnet not engaging, however that car was stock and had some other previous issues, I don't think the owner has fixed it yet.

Easy things to check/do - unplug battery overnight to clear out ECU and adaptations etc. This will not erase your new map. Sometimes these cars see something new, or the connector was unplugged while the car had power and is now confused, so definitely try this first if you haven't already.

Does the connector and visible wires going to it look ok?

You asked about a diode, there is a resistor that is often sent with fixed pulleys that goes in that harness, but based on your post it appears you have a clutched pulley. If they sent a resistor, definitely don't use it. And maybe verify that Tony sent you a map for a clutched pulley (vs FSP).

Good luck!
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Old Jun 22, 2021 | 05:23 PM
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Oh - and the last thing to check is to make sure the radiator cooling fan is plugged back in. Tony's video on install has you unplug it during a map upload, if you forget that could possibly cut things like the SC as a safety precaution until it's plugged back in.
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Old Jun 23, 2021 | 12:07 PM
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Its fairly common at this age for Magnets to fail. If this is the case A clutch delete will remove the whole mechanism. However, If you are able to apply power and engage the SC then you could have a wire issue. Check your IC pump aswell
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Old Jun 25, 2021 | 04:52 AM
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W211 E55 AMG
Thanks for your replies. I have asked my mechanic to crack the connector on the magnet, and yes, there is a diode in there!

also, the diode is fried. We are changing this diode and I will update you afterwards.

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Old Jun 25, 2021 | 11:49 AM
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W211 E55 AMG
This afternoon my mechanic called to tell me that this was indeed the problem.
He changed the diode for a new one, and everything works as it should! The diode he used was a standard 12V diode, which prevents to run a current from the magnet back into the system.

Because the old diode was broken, the car was running in limp mode and the s/c was shut off.

I will give you an update about the invoice...
Have a nice weekend!
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Old Jun 26, 2021 | 03:10 AM
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Originally Posted by Reurda
This afternoon my mechanic called to tell me that this was indeed the problem.
He changed the diode for a new one, and everything works as it should! The diode he used was a standard 12V diode, which prevents to run a current from the magnet back into the system.

Because the old diode was broken, the car was running in limp mode and the s/c was shut off.

I will give you an update about the invoice...
Have a nice weekend!
Excellent! Well done on this. Enjoy the unleashed beast now
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