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Anyone retrofit the alarm siren for option code 551 to a US spec W164?
I'm looking at doing it so I can get the audible lock/unlock notifications - it doesn't seem too difficult at all... The siren is H3/1 on wiring diagrams and it's looking like the mod requires adding one wire to the c connector of the rear SAM at position 43/routing a new wire, a fuse at f110 under the hood, and grounding to w16/3 under the hood... then coding!
The siren looks to be pretty inexpensive, and I've got a spare rear SAM for experimenting...
Guess it's time to fiddle!
Last edited by justinwrock; May 22, 2018 at 04:33 PM.
Should have mentioned, non-US/Canadian spec cars with code 551 have the h3/1 alarm siren with the battery backup, whereas US cars get code 460 for h3 (basic horn) - see below from the MB workshop manual.
Here's a non-US spec W164 with the audible lock/unlock:
Here is the USA wiring diagram. Retrofitting doesn't look that easy.
I've attached the wiring diagram of the rear sam - note at the top of page 6 where h3/1 is listed: we have pin 1 of the alarm siren going to fuse 110 of the main box, pin 2 going to w16/3 (current ground for the stock alarm horn), then pin 3 being connected to c/43 of the rear sam. the connection is made via x25/2 at the firewall and a grey wire in a car equipped with the alarm siren.
My vin starts with a 4.
Retrofit actually looks super simple, the hardest part is going to be running wires and adding a pin to the connector...
I've attached the wiring diagram of the rear sam - note at the top of page 6 where h3/1 is listed: we have pin 1 of the alarm siren going to fuse 110 of the main box, pin 2 going to w16/3 (current ground for the stock alarm horn), then pin 3 being connected to c/43 of the rear sam. the connection is made via x25/2 at the firewall and a grey wire in a car equipped with the alarm siren.
My vin starts with a 4.
Retrofit actually looks super simple, the hardest part is going to be running wires and adding a pin to the connector...
I believe all W164 were made in Alabama, so all of the VIN's start with a 4. The vin starting with W is from Germany, and none of our cars were made there.
Justinwrock, I have looked at the wiring diagrams you posted, and I think you are exactly right.. there are only 3 wires to the siren: from SAM, 12v, and ground.
Rather than going from the fuse box, can't you tap any constant power wire under the hood? And I'm not sure about the alarm siren, but most horns are grounded using the mounting point -- when you bolt it to the car in the assigned spot, it is grounded and no separate wire is required. Your horn is probably wired this way. Verify for sure, but you may not need a separate wire (or can simply run the wire a few inches to the mounting bolt)
It sounds like other than power and ground, you only need that one pin from the SAM. I'd be hesitant to add another pin to a SAM connector.. you would have to be VERY careful not to short circuit or mess up the connector or you could have lots of problems. Maybe the connector already has that wire and you can tap into it? I'd be surprised if MB had a different wiring harness for cars with an alarm siren vs. without.. the wire may already be there and you can tap into it.
Let me know if you get this working.. I'd LOVE to do the same!
As a test, have you tried hooking up a voltmeter to the siren pin in your SAM to see what happens if you lock/unlock your doors? I can give mine a shot, as I have already coded it to chirp the siren.. I just don't have a siren (yet!)
I believe all W164 were made in Alabama, so all of the VIN's start with a 4. The vin starting with W is from Germany, and none of our cars were made there.
Justinwrock, I have looked at the wiring diagrams you posted, and I think you are exactly right.. there are only 3 wires to the siren: from SAM, 12v, and ground.
Rather than going from the fuse box, can't you tap any constant power wire under the hood? And I'm not sure about the alarm siren, but most horns are grounded using the mounting point -- when you bolt it to the car in the assigned spot, it is grounded and no separate wire is required. Your horn is probably wired this way. Verify for sure, but you may not need a separate wire (or can simply run the wire a few inches to the mounting bolt)
It sounds like other than power and ground, you only need that one pin from the SAM. I'd be hesitant to add another pin to a SAM connector.. you would have to be VERY careful not to short circuit or mess up the connector or you could have lots of problems. Maybe the connector already has that wire and you can tap into it? I'd be surprised if MB had a different wiring harness for cars with an alarm siren vs. without.. the wire may already be there and you can tap into it.
Let me know if you get this working.. I'd LOVE to do the same!
As a test, have you tried hooking up a voltmeter to the siren pin in your SAM to see what happens if you lock/unlock your doors? I can give mine a shot, as I have already coded it to chirp the siren.. I just don't have a siren (yet!)
As far as I know, all W164's were built in Alabama - US/Canada market ones got the standard 17 character vin, while ROW cars got the cool 16 character FIN. I believe the W166 is built in 2 plants though - Alabama and at a plant in Asia.
The h3 (alarm horn) might be grounded through the mount, but I know it has a ground wire (verified on my car and on the wiring diagrams). I know the connector/harness doesn't exist under the hood of my car - and suspect that the wire doesn't exist at the rear sam If you're curious, the location for the factory siren would be under the fresh air intake for the heater core on the passenger side of the engine compartment, behind the firewall. Unsnap the silver latches, then remove the two 10mm (or 12mm) nuts holding the air box in, and it should be under there.
I actually thought about it yesterday, and may just mount the alarm siren somewhere in the rear under the bumper... It'd be way easier to install - +12 constant can come from the rear fuse box, ground to the mount/chassis (or at the actual ground next to the rear SAM), then the signal wire only needs to be ran a foot or two. There's even a place on the grommet for the hitch wiring which you can cut and run the wire through.
You could tap any constant +12 source with a fuse under the hood, I just liked the idea of a factory looking install. Figured the 15 minuntes it would take to wire to the OEM spot in the fuse box would have been a drop in the bucket compared to the hour or two it'd take to run the wire from the rear sam to under the hood!
As for checking for the wire/output on the pin - I haven't had a chance. I was planning on actually trying it this weekend while I have my trunk/rear bumper apart to change out the wiring for my hitch. If you do have time to check for the wire/signal on pin c/43, please let us know your findings!
Honestly, I might just take the plunge and buy the parts before poking around. I found a recycler local to me who has the siren/connector with 2 feel of wiring attached for $40, and re-pinning the connector is super-dooper easy! I am going to have my trunk apart, so it would be easy to swap to my old rear SAM for testing so I don't hurt my new one.
Also, I'll definitely let you know what I find this weekend. I really want to make this happen - I can't believe an audible notification for lock/unlock was never a "thing" on US spec W164's!
-Justin
Last edited by justinwrock; May 24, 2018 at 12:21 PM.
Yes, non US-spec MLs for sale in Germany... Though they were manufactured in Alabama then exported to Germany.
Attached is the vin breakdown for the W163, but is applicable to the W164. Basically the character before the chassis number is the indicator for the plant where manufactured, chassis number being the last 6 digits of the VIN/FIN. A is for Alabama, and in all of the cars showing VIN/FINs for sale on that site list an A for the plant where manufactured.
Got the wiring done while installing the hitch wiring! Alarm siren is temporarily just sitting inside the spare tire compartment while I try and sort coding! Hopefully will have some time to work with the coding in the next week or two.
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If you're curious, the location for the factory siren would be under the fresh air intake for the heater core on the passenger side of the engine compartment, behind the firewall. Unsnap the silver latches, then remove the two 10mm (or 12mm) nuts holding the air box in, and it should be under there.
