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Old 03-11-13
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Join Date: Jun 2007
Location: Adelaide
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Default Factory camera and MMCS replacement

Yes, it can be done, and it's not that hard - in hindsight, when you know what to do...

I bought my NT second hand (from a fellow forumite) on a Friday - in Brisbane.

On Monday, while driving back to Adelaide, I decided the MMCS had to go.

Ever the opportunist, I bought an ex-demo unit from another fellow forumite, Extnix. Although it came with an aftermarket camera and all required cables, I decided I would prefer to use the factory camera - if possible.

After pulling apart the dash and extricating the old unit, the connectors on the back of the new unit didn't match the connectors on the wiring diagram I found in the on-line Russian service manuals - see here.





However, the colour-codes of the wires did match, and the modification can be done without cutting a single factory wire.

My new head unit only used two of three multi-pole connectors. The one that wasn't used looked like this:



The pink wire to the camera is the positive power supply - on my NT, it was measuring 6.6V when the camera was active.

The video signal was on white and light green wires - with my el-cheapo multi-meter, measuring AC volts, the measurement went from about .09V with the camera off, to about 0.27V with the camera active.

The other two wires (pink-black and black-yellow) have me bamboozled. They both appear to be earths, they always seemed to have the same voltage (measuring both AC and DC), and the camera would work with either earthed. In the end, I simply earthed them both.

A reversing signal is on the red wire with a green stripe (although it looked more black to me...) Upstream of the diagram I posted above, it comes from an ignition-switched supply, via a fuse and transmission switch - it's essentially a +12V supply that's only on when the ignition is on, and the transmission is in reverse.

So - the Paj provides a +12V source when reverse is selected, but the camera needs +6.6V. So I bought a 6V regulator (LM7806), wired it up and hooked up the camera - no good.

Sleeping on it, I concluded the next step was to up the voltage - Mitsubishi was feeding the camera 6.6V, maybe 6V wasn't enough. I modified the regulator circuit (two extra resistors, but it meant I needed to move everything to a small PCB) and (through trial and error - I was too lazy to look up specs and do the calcs) I produced 7V. (For the record, 3k3R between output and ground terminal, then 120R between ground terminal and vehicle ground.) This worked fine without load, but dropped to 5V under load, which caused the regulator to get very hot. Surprisingly, the camera was working and producing video, but the heat was disturbing. I measured the camera load at about 80mA, which shouldn't stress a regulator rated for 1A. I even considered adding a heatsink, but calculated heat dissipation was well within published specs.

After more thought, I decided to stop being lazy, and install a 100uF capacitor on the regulator input, as recommended in Fairchild's data sheet. Worked out how to add it to my cut-down piece of PCB, and gave it a test. All good. Stable 7V, and cool regulator.

Even the video connection was quick & easy (aka cheap & nasty). I had a damaged RCA cable that I didn't see myself ever using again, so I chopped the yellow lead off, and stripped the end. It's not even coax, but I twisted and tinned the ends, then poked them into the factory sockects on the white ("signal") and green ("shield") wires. By deliberately selecting the reversing camera input on the new headunit, I could see the picture on the camera - a fraction noisier than I remember the MMCS picture, but I'll live with it.

The last step was to find a signal to tell the new head unit that the camera was required. Theoretically, the new head unit was supposed to receive an appropriate signal via canbus, but (as Extnix had warned me) this didn't work. I already had +12V on my PCB whenever I wanted the camera, so I added another wire to feed that signal into the head unit. Problem solvered!

For the record, the factory multi-pole connector comes apart, so individual wires can be removed. Unfortunately, all the wires come loose at once, so I am very pleased that I thought to take multiple photos before I started. Ultimately, I removed the wires I wanted, then simply poked new wires into the individual sockets. Theoretically, I can restore the connector to the factory configuration at any stage - but I really don't know why I bothered. It would be almost as easy to simply poke wires into the relevant parts of the factory socket, and probably more reliable to simply cut the factory harness and solder new wires as required.

Anyway, it's done. I'm using the factory camera with an aftermarket head unit, and didn't cut a single factory wire.
Attached Images
File Type: jpg Connector.jpg (137.7 KB, 306 views)
File Type: jpg Rear View Camera.jpg (94.3 KB, 314 views)
File Type: jpg Reverse Switch.jpg (34.4 KB, 305 views)
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NT Platinum. DiD Auto with 265/70R17 Toyo MT, Lift, Lockers, Lockup Mate, Low range reduction, LRA Aux tank, bull bar, winch, lots of touring stuff. Flappy paddles. MMCS is gone!

Project: NJ SWB. 285/75R16 ST Maxx, 2" OME suspension, 2" body lift, ARB 110, 120l tank, bullbar, scratches, no major dents. Fully engineered in SA. NW DiD & auto in place - a long way to go....

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