another w204 backup camera problem
Thread Starter
Newbie
Joined: Jan 2019
Posts: 6
Likes: 0
c300 4matic 2010
another w204 backup camera problem
i have been working on this backup camera on my wife's 2010 c300 since yesterday morning. it's killing me.
what i've done:
installed camera to trunk lid and made appropriate connections
routed video cable to COMAND unit
connected fakra/rca adapter, connected video line to COMAND
enabled SRVC in eng.menu
system reset
what it's doing:
shift into reverse, black screen with text and guidelines
troubleshooting:
1. removed fakra/rca adapter, brought an extensions cord and 19" tv out to the car, and confirmed that the camera is outputting video to the end of the line
no way to test throughput of fakra/rca adapter
2. reconnected original green fakra for iPod kit, connected old Nintendo
deactivated SRVC in eng.menu, corrected setup for aux.video
switch input to aux video with OEM connections: black screen
tried connecting nintendo to 4pole 3.5mm multiplug, still black screen
tried connecting nintendo with new fakra/rca adapter, still black screen
3. visual inspection of fakra port on COMAND unit, it looks fine
visual inspection and comparison of OEM and new fakra plugs, both look the same and fine
4. confirmed NTSC settings in COMAND
the only thing i haven't tried is loading a video on this ancient iPod i have, and trying to play aux video through the 30pin dock connector
has anybody else encountered this? the troubleshooting i've performed indicates that my COMAND unit isn't capable of accepting/displaying video through the aux fakra. that would be a terribly inconvenient truth.
what i've done:
installed camera to trunk lid and made appropriate connections
routed video cable to COMAND unit
connected fakra/rca adapter, connected video line to COMAND
enabled SRVC in eng.menu
system reset
what it's doing:
shift into reverse, black screen with text and guidelines
troubleshooting:
1. removed fakra/rca adapter, brought an extensions cord and 19" tv out to the car, and confirmed that the camera is outputting video to the end of the line
no way to test throughput of fakra/rca adapter
2. reconnected original green fakra for iPod kit, connected old Nintendo
deactivated SRVC in eng.menu, corrected setup for aux.video
switch input to aux video with OEM connections: black screen
tried connecting nintendo to 4pole 3.5mm multiplug, still black screen
tried connecting nintendo with new fakra/rca adapter, still black screen
3. visual inspection of fakra port on COMAND unit, it looks fine
visual inspection and comparison of OEM and new fakra plugs, both look the same and fine
4. confirmed NTSC settings in COMAND
the only thing i haven't tried is loading a video on this ancient iPod i have, and trying to play aux video through the 30pin dock connector
has anybody else encountered this? the troubleshooting i've performed indicates that my COMAND unit isn't capable of accepting/displaying video through the aux fakra. that would be a terribly inconvenient truth.
Thread Starter
Newbie
Joined: Jan 2019
Posts: 6
Likes: 0
c300 4matic 2010
well, as it would seem, this fakra/rca adapter has a short circuit, the two poles show continuity.
does anybody know if that could/would damage the COMAND unit?
i never tested the aux.video functionality before connecting the backup camera, but i've pulled the COMAND unit and i'm measuring 78ohms of resistance between the inner pin and the sheath.
i'm not particularly knowledgeable about "what to expect" but the internet says i should expect 75ohms resistance on a coaxial a/v/data line, compared to the .8ohm short on this fakra adapter.
this stinks
does anybody know if that could/would damage the COMAND unit?
i never tested the aux.video functionality before connecting the backup camera, but i've pulled the COMAND unit and i'm measuring 78ohms of resistance between the inner pin and the sheath.
i'm not particularly knowledgeable about "what to expect" but the internet says i should expect 75ohms resistance on a coaxial a/v/data line, compared to the .8ohm short on this fakra adapter.
this stinks
Last edited by Ronnoc Nailli; Jan 13, 2019 at 06:45 PM.
Super Member
Joined: Mar 2011
Posts: 803
Likes: 37
From: Bay Area, CA
2011 C300 Sport, P1, MM, Wood, Heated FS, DIY rearview camera.
75 ohm is the characteristic impedance of a video coaxial cable, not the DC resistance measured with a DMM. Any coaxial cable should be DC open between the center conductor and the outer shield.
Thread Starter
Newbie
Joined: Jan 2019
Posts: 6
Likes: 0
c300 4matic 2010
well shoot.
-1 for my tenuous grasp of low voltage electronics
i measured the resistance between center and shield on the COMAND unit, which read ~75ohm as opposed to the cable's 2-3ohm.. to quote cablesondemand:
“The characteristic impedance of the coaxial cable (in Ohms) is determined by the dielectric constant of the inner insulator and the radii of the inner and outer conductors.”
which to me reads, the impedance between inside and outside.
operating under the assumption that i correctly understood the situation, i completed the repair and thankfully it worked.
-1 for my tenuous grasp of low voltage electronics
i measured the resistance between center and shield on the COMAND unit, which read ~75ohm as opposed to the cable's 2-3ohm.. to quote cablesondemand:
“The characteristic impedance of the coaxial cable (in Ohms) is determined by the dielectric constant of the inner insulator and the radii of the inner and outer conductors.”
which to me reads, the impedance between inside and outside.
operating under the assumption that i correctly understood the situation, i completed the repair and thankfully it worked.
Junior Member
Joined: Jan 2014
Posts: 46
Likes: 0
From: Seattle, WA
2012 C300 4Matic
Guys, i also got everything wired up and the screen shows nothing when in reverse. I dont have any monitor/tv to test out if the camera works or not. is there any other way i can test to see if camera outputting anything? i bought camera and fakra cable almost 4 years ago.. just got to install it.. so not sure if camera is still working.
Thread Starter
Newbie
Joined: Jan 2019
Posts: 6
Likes: 0
c300 4matic 2010
i found that the FAKRA adapter was difficult to fully seat into the COMAND unit. i ended up removing the plastic jacket and inserting the core connector only. it's still a snug fit, and that made plugging in the LVDS connector next to it easier
without having a TV or screen of some sort to test the camera, there's not a whole lot you can try...
use a multimeter or the like to test the power/ground at the camera when it should be on
test the continuity of the video cable you've run to the COMAND unit
test the continuity of the RCA/FAKRA adapter (if you've bought cheap chinese one like me, it may be bad or out of spec for the job)
if the camera isn't fully installed to the trunk lid, you may consider bringing the camera inside and connecting to your home TV, and trying to find a 12v power supply to turn it on there.
you could also enter the engineering menu and disable SRVC and enable AUX.video... then select AUX.video on the COMAND unit... this could possibly determine that the camera is correctly installed and that the SRVC isn't configured correctly in COMAND.
good luck
without having a TV or screen of some sort to test the camera, there's not a whole lot you can try...
use a multimeter or the like to test the power/ground at the camera when it should be on
test the continuity of the video cable you've run to the COMAND unit
test the continuity of the RCA/FAKRA adapter (if you've bought cheap chinese one like me, it may be bad or out of spec for the job)
if the camera isn't fully installed to the trunk lid, you may consider bringing the camera inside and connecting to your home TV, and trying to find a 12v power supply to turn it on there.
you could also enter the engineering menu and disable SRVC and enable AUX.video... then select AUX.video on the COMAND unit... this could possibly determine that the camera is correctly installed and that the SRVC isn't configured correctly in COMAND.
good luck
Last edited by Ronnoc Nailli; Jan 19, 2019 at 07:37 PM.
Trending Topics
Junior Member
Joined: Jan 2014
Posts: 46
Likes: 0
From: Seattle, WA
2012 C300 4Matic
i found that the FAKRA adapter was difficult to fully seat into the COMAND unit. i ended up removing the plastic jacket and inserting the core connector only. it's still a snug fit, and that made plugging in the LVDS connector next to it easier
without having a TV or screen of some sort to test the camera, there's not a whole lot you can try...
use a multimeter or the like to test the power/ground at the camera when it should be on
test the continuity of the video cable you've run to the COMAND unit
test the continuity of the RCA/FAKRA adapter (if you've bought cheap chinese one like me, it may be bad or out of spec for the job)
if the camera isn't fully installed to the trunk lid, you may consider bringing the camera inside and connecting to your home TV, and trying to find a 12v power supply to turn it on there.
you could also enter the engineering menu and disable SRVC and enable AUX.video... then select AUX.video on the COMAND unit... this could possibly determine that the camera is correctly installed and that the SRVC isn't configured correctly in COMAND.
good luck
without having a TV or screen of some sort to test the camera, there's not a whole lot you can try...
use a multimeter or the like to test the power/ground at the camera when it should be on
test the continuity of the video cable you've run to the COMAND unit
test the continuity of the RCA/FAKRA adapter (if you've bought cheap chinese one like me, it may be bad or out of spec for the job)
if the camera isn't fully installed to the trunk lid, you may consider bringing the camera inside and connecting to your home TV, and trying to find a 12v power supply to turn it on there.
you could also enter the engineering menu and disable SRVC and enable AUX.video... then select AUX.video on the COMAND unit... this could possibly determine that the camera is correctly installed and that the SRVC isn't configured correctly in COMAND.
good luck
i should be able to remove it from the trunk lid. i didnt seal the trunk yet so i'll be able to take it out. I checked the wires and they all are securely connected. also i pushed the fakra the way in to make sure it was securely connected. but yes if the issue is cable like yours then i'm screwed.
thanks for the suggestions..
MB World Stories
The Best of Mercedes & AMG
Flawlessly Restored Mercedes 190E Evo II Heads to Auction
Verdad Gallardo
Electric Mercedes C-Class Unveiled: 11 Things You Need to Know
Verdad Gallardo
Mercedes EQS Gets A Major Update: Everything You Need to Know
Verdad Gallardo
5 Underrated Mercedes-Benz Models That Don't Get the Love They Deserve
Verdad Gallardo
Mercedes 300D Has Pushed Well Past 1 Million Miles and It Ain't Stopping
Verdad Gallardo
10 Most Reliable Mercedes-Benz Models You Can Buy Used
Verdad Gallardo
Mercedes Teases Updated EQS With Steer-By-Wire and a Yoke
Verdad Gallardo
8 Mercedes Models With Poor Reliability Records
Verdad Gallardo
Magnificent New Mercedes-Maybach S-Class Revealed: 12 Things to Know
Verdad Gallardo
Junior Member
Joined: Jan 2014
Posts: 46
Likes: 0
From: Seattle, WA
2012 C300 4Matic
Junior Member
Joined: Jan 2014
Posts: 46
Likes: 0
From: Seattle, WA
2012 C300 4Matic
