Aftermarket amp wire - battery or rear SAM/ fuse box
Thread Starter
Junior Member
Joined: Sep 2012
Posts: 22
Likes: 0
From: Montreal Canada eh
2009 C300
Aftermarket amp wire - battery or rear SAM/ fuse box
I am installing an aftermarket amp and sub in the car and I am at the last step - trying to find a place for my POS amp wire.
I have searched for hours online and saw one thread on here where a guy found a spare grommet at the passenger side below the dash - that same grommet on my car (maybe because mine is a Canadian car) has a grey tube in it and cannot be used.
I have heard people saying they used the rear SAM module (fuse box) in the trunk... I looked and it looks do-able but just not sure how - I've always used the battery! there are 2 heavy gauged red wires there but does anyone know how you tap into such big wires with another big wire?
Or can anyone else suggest how to get the wire from the battery to inside the car
My car is totally taken apart and I am just waiting on this final piece of the puzzle before closing everything up and enjoying some nicely added bass!
I have searched for hours online and saw one thread on here where a guy found a spare grommet at the passenger side below the dash - that same grommet on my car (maybe because mine is a Canadian car) has a grey tube in it and cannot be used.
I have heard people saying they used the rear SAM module (fuse box) in the trunk... I looked and it looks do-able but just not sure how - I've always used the battery! there are 2 heavy gauged red wires there but does anyone know how you tap into such big wires with another big wire?
Or can anyone else suggest how to get the wire from the battery to inside the car
My car is totally taken apart and I am just waiting on this final piece of the puzzle before closing everything up and enjoying some nicely added bass!
MBWorld Fanatic!
Joined: Dec 2007
Posts: 3,056
Likes: 47
From: Orlando, Florida
E350 Sport/ML350RWD
I have installed many competition audio systems with no issues. This is the first car I took to a shop for an install. The problem is everything is so tight it is nearly impossible for me to fit my hands anywhere. It wasn't worth it for me to take a chance of screwing up something expensive.
If you are installing heavy gauge wire- I (and the high-end shop I used) do not recommend tapping into the rear fuse box. Clean power from the battery is the only way as far as I am concerned. If you are running 16g for a Bazooka ro something small- MAYBE it would work but I have never seen anyone include detailed pics of how they tap into the rear block.
Sorry I can't help more.
If you are installing heavy gauge wire- I (and the high-end shop I used) do not recommend tapping into the rear fuse box. Clean power from the battery is the only way as far as I am concerned. If you are running 16g for a Bazooka ro something small- MAYBE it would work but I have never seen anyone include detailed pics of how they tap into the rear block.
Sorry I can't help more.
Super Member
Joined: Oct 2007
Posts: 642
Likes: 1
From: Natick, MA
2010 C350 Sport
There is a grommet near the battery that you can take out and pass the wire through. It is to the right of the battery if you are looking at the battery from the front of the car. Pop the grommet out and you will be set. You will need to pull the carpet up from the inside of the car as well, I used a snake and the job was pretty easy.
Thread Starter
Junior Member
Joined: Sep 2012
Posts: 22
Likes: 0
From: Montreal Canada eh
2009 C300
Do you have to take the battery out to see it? I know there is someone on here that had pics of the grommet he used and he had to remove the battery to see it... And he also had a pic of the grommet from the inside passenger compartment... And that grommet on my car has a grey tube in it for some reason (maybe cause my car is a canadian model)
Anyhow, I will look tomorrow around the battery...
Anyhow, I will look tomorrow around the battery...
Member
Joined: Oct 2010
Posts: 139
Likes: 1
From: Virginia
2010 C350, 2011 BMW 328xi
I have been researching this as I am going to do a HK Amp retrofit. If you look in the read SAM there is a relay box for fuses, slot 67 through 73. 67 is the slot for the sound system if your car originally came with the code 810 HK Amp. This would be an excellent place to tap into. The other slots occupied are 70, 71, and 72 which are the cigar lighter, power to the power outlet in the glove box, and power outlet to the center console for the rear passengers. You would need a 40 amp fuse and the connector that attaches to the power wire and fits in the relay box. Relay box separates from the SAM very easily to do the install. I don't know the part number but hopefully going to the merc dealer today to get it--will update you when I have it in case you want to go this route. will your amp pull more than 40 amps?
Super Member
Joined: Oct 2007
Posts: 642
Likes: 1
From: Natick, MA
2010 C350 Sport
Do you have to take the battery out to see it? I know there is someone on here that had pics of the grommet he used and he had to remove the battery to see it... And he also had a pic of the grommet from the inside passenger compartment... And that grommet on my car has a grey tube in it for some reason (maybe cause my car is a canadian model)
Anyhow, I will look tomorrow around the battery...
Anyhow, I will look tomorrow around the battery...
There is also another grommet behind the battery that you can use if you take it out.
I would not tap the rear SAM, I would find a way to get power directly from the battery.
Thread Starter
Junior Member
Joined: Sep 2012
Posts: 22
Likes: 0
From: Montreal Canada eh
2009 C300
Ok i think I found it..
Is that it in the pic below? it's more like a plastic cap and not the usual rubber grommet, can this be?
And can I just drill a a small hole in the center instead of removing it?
And then put a little silicone afterwards...
Is that it in the pic below? it's more like a plastic cap and not the usual rubber grommet, can this be?
And can I just drill a a small hole in the center instead of removing it?
And then put a little silicone afterwards...
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Super Member
Joined: Oct 2007
Posts: 642
Likes: 1
From: Natick, MA
2010 C350 Sport
Yes that is it. I do remember it begin plastic on mine as well. I drilled a hole in it as well and fed the wire through. Drill it the right size and you really won't even need the silicone.
You will probably need to remove it to drill it though. It is easier to remove from the inside while pushing to towards the battery opening.
You will probably need to remove it to drill it though. It is easier to remove from the inside while pushing to towards the battery opening.
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From: Miami Beach/Madison
'09 S550-4 W221 '18 S560-4 W222 & '14 S550-4 W222
You may have the ticket
I have been researching this as I am going to do a HK Amp retrofit. If you look in the read SAM there is a relay box for fuses, slot 67 through 73. 67 is the slot for the sound system if your car originally came with the code 810 HK Amp. This would be an excellent place to tap into. The other slots occupied are 70, 71, and 72 which are the cigar lighter, power to the power outlet in the glove box, and power outlet to the center console for the rear passengers. You would need a 40 amp fuse and the connector that attaches to the power wire and fits in the relay box. Relay box separates from the SAM very easily to do the install. I don't know the part number but hopefully going to the merc dealer today to get it--will update you when I have it in case you want to go this route. will your amp pull more than 40 amps?
What did you learn at the dealer, I'm planning to connect a 400w bridged, 200 RMS amp to the 8-10AWG power wire going into the SAM using a 3-way connection fuse block sort of deal that goes from 2 4-8AWG (2) to 0/1-4AWG (1) with a 60amp fuse (that I can swap out for a 40 or 50 if need be). But tapping right into the fuse block, esp with some sort of Merc part seems a lot wiser/easier.
Note: i realize getting power direct from the battery is ideal, although in my case where I only be using the setup for maybe 3-4 months, this seems a lot more feasible to me, despite the potential drawbacks (short of ruining something very expensive 🫰🏽 😞
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