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#16
03-14-2019, 10:10 AM
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Quote:
__________________
'85 300D - federal spec, built in late 84. 85 300D Complete AC System Rebuild 
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#17
03-14-2019, 11:03 AM
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Pic attached. Looks like it's the 10mm allen screw.
So, i'm having trouble following the situation. Does this mean that the Momo adapter linked to above, WILL fit my vehicle on the column end of things? I guess i'm wondering about the spline business. I guess if that works out fine, then it's just down to the 70mm bolt diameter, which i do believe is already settled with this steering wheel and this momo adapter. As for the horn button... I'll take a look at the dual contact situation, but i'm assuming that can be modified easily to just be a regular SPST switch and not a DPST sorta thing. I'm assuming Mercedes simply doubled up on the one contact end of things so as to always guarantee action. I could maybe even install a second contact wire somewhere in the new wheel so that the vehicle follows the safety standard that Mercedes requires. 
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#18
03-14-2019, 11:49 AM
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It's not a redundancy thing. The MB horn button is a switch the closes + lead to the horn, so the contacts need to isolated from ground. In most other cars the horn button closes the ground so it only needs a single contact.
And yes, the 10mm allen screw means that the Momo adapter linked previously will work.
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#19
03-14-2019, 12:33 PM
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All right well i ordered the steering wheel.
Assuming the worst about the button hole and that a momo-merc three point button won't install, I'm comfortable with having to do some sort of serious electronic workaround to get the connections working. I work with electronics on a daily basis so can figure something out. They weren't able to provide any pics of wheel without the button, nor give a diameter of the hole. But based on pics it sure looks very similar to the momo size, and their own brand of horn buttons for sale seem to be standard for "all wheels". So fingers crossed. The momo hub adapter seems to be a match on both ends. Fingers crossed on that too though. You never know.
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#20
03-14-2019, 01:03 PM
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So long as you receive the correct, non-defective part it is the correct hub for your car.
For the steering wheel, can't really tell what size the horn button hole is because the one it comes with has a built in trim ring kinda thing. Hopefully it has Momo horn button diameter, because your hub will. Nardi horn button is slightly larger. Not bad looking though. It's like a knockoff of the wheel in my W201. 
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#21
03-15-2019, 05:10 PM
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Quote:
But yeah it does seem like this whole brand of wheels is meant to work together nicely with Momo and a few other parties specifically. So i could always go about tracking down an actual Momo horn button... that was designed with Mercedes' three point electronics switch? Is that what i'd look for ? The dealer that carries the hub adapter actually went ahead and reached out to Momo on my behalf and got back to me with some numbers about the spline end of things.. "spline count 76 and 23mm diameter" Just thought i'd post that info here! I assume those are the numbers for these later W123's and other series going forward as mentioned previously in this thread.
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#22
03-15-2019, 06:17 PM
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Steering Wheel Fun
PING ! I just sent you an E-Mail, it might go into your spam folder .
__________________
-Nate 1982 240D 408,XXX miles Ignorance is the mother of suspicion and fear is the father I did then what I knew how to do ~ now that I know better I do better
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#23
03-15-2019, 06:21 PM
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Quote:
Try sending a PM message directly in forum messags maybe?
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#24
03-16-2019, 12:19 AM
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Here's an example of a MB-Momo horn button, and yes they have dual contacts.
Can sometimes find them a bit cheaper. I bought and sold one because the Momo OD is a little smaller than Nardi horn button ID, so there was a gap and couldn't use the trim ring. Then later I lucked out and found the MB-Personal horn button in the above photo. I've seen some stick-on adhesive wheel center caps that might work with the horn button on that steering wheel you bought. Take some measurement when you get it and eventually you'll find something to spiff it up. There are also off-brand horn buttons with MB logos. Many of them are made using single contact horn buttons, so just be sure to verify with the seller if you go to purchase one.
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#25
03-19-2019, 07:16 PM
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Ok, please see attached. This is the inside of the new wheel just received.
Can someone please relay info about the electronic difference between this and the proper mercedes connections? Looking at the ebay link to the Momo horn button ( There are two connection points in both horn button design. Can i just hook this thing up?
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#26
03-19-2019, 10:27 PM
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It's probably safe to assume that's a normal dual contact horn button. The back of the Momo in your link looks more/less the same. There are two spade connectors.
 If you want to be sure use a multimeter to verify function of the switch. The contacts should be isolated from the body of the horn button and close when it's pressed.
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#27
03-20-2019, 10:48 AM
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Yeah when i get to finally dive in with this next week i'm going to put a multimeter to the OEM wheel horn first and see what's actually going on and then do the same for this button. It's not clear to me what the situation is right now.
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#28
03-20-2019, 11:26 AM
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Not much to understand. It's just switched 12V going to the horn. Horn button is no different than a light switch or any other switch.
Like mentioned before, most other cars have switched ground for the horn. So a single hot lead goes to the horn button and it grounds through steering wheel when the button is pressed. Worst case is you blow a fuse if that horn button is incorrect somehow.
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#29
03-20-2019, 11:37 AM
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Oh. So it’s just that Mercedes decided that they wanted to be patching 12V around instead of patching ground around. Gotcha. So basically the two connectors need to have nothing to do with ground otherwise we sink our 12V when button is pressed.
So if this new horn button’s two contacts don’t beep out to gnd on the continuity checker, then I suppose this horn button will wire up fine with a Mercedes. I guess I’ll do a check for this. But maybe back in the w123 wheel connections there is a third ground wire I can just omit from the new button or something.
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