This is progressing slower than I would like, but I passed my last technical risk for a minimal level of functionality. I was concerned about the overall cable length and connector loss with a connector at the hitch and more than twice as much cable as the infotainment kit came with (and likely an OE installation). With this in mind I purchased 25m (~80') of what I think is the best quality / performing cable available which is still small enough to work with Fakra connectors. What is discovered is connectors claiming to be compatible with RG-316 are not exactly compatible with RG-316DS (dual shield) and RG-316DS cable is expensive. I ordered the following from Digikey:
Digikey: 3628-22510218-DS-ND MFG : Huber+Suhner, Inc. / K_02252_D
Digikey: WM10362-ND MFG : Molex / 0734036262
Digikey: WM10369-ND MFG : Molex / 0734036282 (This is the wrong p/n (C key, blue) to connect to the mirror! The infotainment plug Z key (water blue, equivalent to Molex 73403-6290).)
The electronics lab tech at work assembled the connectors for me, using a Amphenol? crimper with SMB dies. He commented the connectors weren't intended to be used with dual shield cable (he had to thin the braid to fit the crimp tube), the SMB dies weren't ideal for the center contact but worked, they were the correct size for the crimp tube and something about me being impatient, which i ignored. I took his recommendation to install connectors on both ends of the spool and test the connection before cutting the cable to the lengths I need.
Before leaving the office, I had to test the cable. This is when I discovered the mirror connection was not C key. The infotainment cable has a Z key plug (mirror end) and a C key jack (camera end). The camera is very obviously C key (has blue band on die cast plug). The mirror jack is dark (black, or brown?) and difficult to see with the mirror installed. It's obviously not C or Z key (Z is universal), but I can't tell for certain if its A (black), F (brown) or something else without a flashlight and moving the mirror. I modified my C key to a Z key by shaving off the 2 keying ribs with a pocket knife. Everything was finally connected (we also installed the connectors on wrong ends of the spool so I had unspooled 80' of cable into the passenger foot well) and flipping the toggle yielded a clear image on the mirror. I could drive home happy.
Once home, I tried my 25m (80') cable as an extension on the infotainment 25' cable, to test signal integrity margin. This introduces signal loss via an additional connector pair (I'll have a pair at the hitch and another pair near the rear fuse panel (to select the lift gate camera)) and 25' of lower quality RG-174 cable. Considering my final cable length will be approximately 60', I likely could have purchased 1/2 as much RG-174 (at 20% the cost per meter of RG-316DS and still Huber+Suhner), used the infotainment cable to get to the hitch and saved several hundred dollars.
My next steps are to determine the length of each section, have the additional connectors installed, 3D print a housing for the camera, install then further testing on a 1500km tow to my parents place.
Additional notes and observations:
- the Fakra housings (at least these Molex ones) are easy to install and remove. This will come in handy for pushing cables with connectors pre-installed through grommets and to change the housing to a different key is necessary.
- these are not waterproof connectors. I'm going to use these as is for my upcoming trip and will wrap in electrical tape when not in use (and may tape the connection for this trip). Longer term I may investigate adapting the OE 7 pin + 2 video connector (I'm not a huge fan from photos I've seen online) or an IP67+ rated connector which can also be capped to protect the unmated contacts. There are IP69 rated Fakra connectors but I haven't found any which are water tight in the unmated condition.
- this is as (or more) expensive than the ZM1 option with GM trailer camera and will yield a different user experience. I would have purchased the ZM1 option if available and likely would have been satisfied with it. I think glancing in the interior rear view mirror to see traffic behind me (as I do without the trailer) will superior to looking a the dash. There are clearly uses where the ZM1 option is superior, such as backing guidance, integration with the side cameras, exterior and interior cameras, checking an option box vs dumping many hours into researching a diy option, etc.
Jeff