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I think that's right. Car starts up, it's sending a signal to close the relay (disconnect aux battery from the main charging loop), and the relay won't close. That condition is causing ECO mode to become disabled. Think I am at a dead end absent diagnostics now.
If you look at the wiring diagram, There’s a fuse for that ECO circuit, I believe it’s internal in the rear SAM.
You should. Probably diagnose in XENTRY as it will be easier than pulling the SAM.
Normally that is a non-serviceable item and dealer just replaces the SAM, but those MIDI/AMI fuses are available if this turns out to be the issue.
Last edited by crconsulting; 02-01-2023 at 08:19 PM.
Awesome - thank you. Didn't appreciate they were serviceable. Maybe if I am feeling daring I will pull it out and see if there is anything amiss. Does the fuse and relay panel separate from the SAM unit?
Awesome - thank you. Didn't appreciate they were serviceable. Maybe if I am feeling daring I will pull it out and see if there is anything amiss. Does the fuse and relay panel separate from the SAM unit?
(I wouldn’t pull anything yet 😀 ) Actually looking at that circuit again, it looks like it’s possible there’s a pre fuse block that contains that fuse on the r231, maybe not the SAM as on some cars. Do you see one of these? (I doubt that’s it because you’d have a non-start condition.) At this point, I think there is definitely another fuse associated with that Aux battery. The wiring diagram definitely shows it. Just a question of where it is. SAM settings are typically also backed up via XENTRY when swapping or working on SAMs, so be careful.
Good Luck!
Last edited by crconsulting; 02-02-2023 at 11:33 AM.
Reason: wrong fuse block
(Don’t pull anything yet 😀 ) Actually looking at that circuit again, it looks like it’s possible there’s a pre fuse block that contains that fuse on the r231, maybe not the SAM
Do you see one of these? (I doubt that’s it because you’d have a non-start condition.) At this point, I think there is definitely another fuse associated with that Aux battery. The wiring diagram definitely shows it. SAM settings are typically also saved via XENTRY when swapping SAMs
It's not immediately jumping out to me. Is there somewhere specific I should be looking?
It's not immediately jumping out to me. Is there somewhere specific I should be looking?
It’s in the front, #175 in diagram below,
Sorry but it’s unclear if that’s actually the circuit going to the Aux battery vs main, without being on site to confirm 100%
You may be able to tell on the car….
Last edited by crconsulting; 02-02-2023 at 11:34 AM.
Reason: Wrong fuse block
It’s in the front, #175 in diagram below,
Sorry but it’s unclear if that’s actually the circuit going to the Aux battery vs main, without being on site to confirm 100%
You may be able to tell on the car….
Great. Will go searching and revert back in a bit.
Found it….
Ignore post 30 & 32 😀
Just looking thru the WIS, you’re looking for this pre-fuse relay box in your car, it’s associated with the ECO function.
See attachment below of what you’re looking for. It’s not #175. (sorry, kinda working blind over the ‘net) But rather look at the front, at the + jumper terminal (look for the IM1 circuit)
See second page- with B03 ECO. It looks closer to picture in post #26 above but not part of the SAM itself.
Last edited by crconsulting; 02-01-2023 at 11:08 PM.
Having trouble bridging from the jump start point (the red circular post) to finding the prefuse box. Maybe it's buried under some of the cladding?
This is the part you’re looking for below: PN 231-540-10-50-64
It’s in series with that + jumper cable. (says right front floor)
Hard to tell exactly where from illustration….
Look for this MIDI/AMI fuse inside the part above “pre fuse relay box”
From PDF in post #34
Last edited by crconsulting; 02-02-2023 at 11:29 AM.
This is the part you’re looking for below: PN 231-540-10-50-64
It’s in series with that + jumper cable. (says right front floor)
Hard to tell exactly where from illustration….
Doesn’t jump out under the hood. May need to get under the car later and see if I can find it.
So I have resigned myself to taking it to the dealer this week. To get it ready for that trip, I am trying to undo the wiring left by the stereo shop (since I am not entirely trusting of the stereo shop's skills). Do you happen to have the wiring diagram for the HK amp under the smuggler's box? In the harness going into the amp, there are two wires twisted together that don't run into the amp (red arrow in my poor photo, below). I am not sure if that's something the shop did or if that is OEM. The other wiring I can figure out. I also can't seem to remove the harness connector from the amp.
So I have resigned myself to taking it to the dealer this week. To get it ready for that trip, I am trying to undo the wiring left by the stereo shop (since I am not entirely trusting of the stereo shop's skills). Do you happen to have the wiring diagram for the HK amp under the smuggler's box? In the harness going into the amp, there are two wires twisted together that don't run into the amp (red arrow in my poor photo, below). I am not sure if that's something the shop did or if that is OEM. The other wiring I can figure out. I also can't seem to remove the harness connector from the amp.
Thanks!
I wired the amp back to stock and left that bundle of blue wires (four of them) alone since they didn’t appear to serve any function. All speakers are working, so seemed to work.
I wired the amp back to stock and left that bundle of blue wires (four of them) alone since they didn’t appear to serve any function. All speakers are working, so seemed to work. will report back on my dealer experience shortly.
Been traveling, so away from my shop/WIS, but sounds like you got your wiring back to somewhat original configuration…..
Dealer will probably just replace that pre-fuse block above. Hopefully the only damage…
Been traveling, so away from my shop/WIS, but sounds like you got your wiring back to somewhat original configuration…..
Dealer will probably just replace that pre-fuse block above. Hopefully the only damage…
Good Luck, let us know how it goes.
Thank you, sir. The rear speakers all seem to be working, so I guess my wiring job worked. I am assuming that the bundle of random blue wires taped off was OEM (the tape was different than the shop tape). Looking at some other HK Logic 7 systems in other MBs, it looks like that bundle was meant to deal with a bass amplifier that I do not think the R231 has.
Merc says bad front prefuse box and quoting $1K to replace. Probably going to have them do it and put this long national nightmare behind me.
I believe the tech at the dealer made the correct diagnosis, which can be half the battle. They won’t change just the fuse in the pre-fuse box, but it’s worth the money to get your car operational. 👍
And, you saved some money by replacing the relay. Dealer would have probably charged $700 (or more) for that.
Moral of the story here is be careful when modifying electrical in these cars. They are pretty sensitive….
I believe the tech at the dealer made the correct diagnosis, which can be half the battle. They won’t change just the fuse in the pre-fuse box, but it’s worth the money to get your car operational. 👍
And, you saved some money by replacing the relay. Dealer would have probably charged $700 (or more) for that.
Moral of the story here is be careful when modifying electrical in these cars. They are pretty sensitive….
Good Luck!
Amen, brother. I’ve asked for the old box back so I can take it apart and test it with my multimeter. May as well use it as a learning experience!
I appreciate all of your help. I will definitely post the outcome once I get the car back from Mercedes early next week.
I’ve learned my lesson - no more electrical tinkering. It’s a shame because others on this forum have clearly installed these amps without issue by running the power to the Rear SAM and using an empty fuse slot. How the shop got the idea to wire directly into a high amperage relay network is beyond me.
Amen, brother. I’ve asked for the old box back so I can take it apart and test it with my multimeter. May as well use it as a learning experience!
I appreciate all of your help. I will definitely post the outcome once I get the car back from Mercedes early next week.
I’ve learned my lesson - no more electrical tinkering. It’s a shame because others on this forum have clearly installed these amps without issue by running the power to the Rear SAM and using an empty fuse slot. How the shop got the idea to wire directly into a high amperage relay network is beyond me.
End of the story - just got the car back from Mercedes:
Front prefuse box was replaced. Old one looked pristine.
Everything is working again.
I disassembled the old prefuse box (doing some damage to the plastic case trying to get it open - now I know why they say it isn't serviceable). Multimeter continuity test showed the 200amp fuse on the IM1 circuit was blown - that's the culprit here as my helpful friend in this thread thought.
It's a shame that a $0.50 cent fuse in a plastic box necessitates replacing a $450 box, but what can you do. For folks who feel like trying to take it apart themselves, be super patient and work around the plastic. It's brittle and wants to break apart.
Labor to get to this thing on the R231 is a beast.
May others learn from my misfortune! Never let anyone hook anything to the IM1 circuit!
Appreciate all of your help and expert diagnostic skills. Now to enjoy my R231 (by turning off the ECO feature I just fixed).
Next items on the list . . . sacrificial harnesses for the cam magnetic adjusters (no oil leaks yet, but figure it's cheap insurance) and replacing my worn out driver's door arm rest.
02-01-2023, 08:09 PM
