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 #378937  by 00R/T
I can cross another item off the list. Since I’ll be hiding the ATC head, I need to relocate the temperature sensor and aspirator somewhere that they can still sample interior air. Since the thermistor is currently mounted directly to the ATC head PCB, I decided to switch to the unit used in most of the modern FCA vehicles. It’s all integrated in one unit and designed to be installed away from the controls. I’m planning on making a mounting boss for it (probably 3D printed) and finding somewhere to put it. I’ll cut vent holes in the surface, epoxy the boss over them, and mount the sensor to it. I’ll need something relatively flat with enough space behind it and that is exposed to cabin air. I’d also like it to be somewhat inconspicuous in case the slots I make in the panel for air to flow through don’t come out the best. The typical spot nowadays is in the knee bolster, so I’ll probably use that if there’s enough room behind it.

Unfortunately the new unit uses a 47k thermistor instead of the 10k in the ATC head. It’s a nice, small, epoxy dipped piece that the sensor is designed around. I was able to find comparable 10k ones, but after doing testing at various temperatures I found that the one used in the head has a very unusual temperature curve that didn’t match anything I could find. So, I desoldered it from the head and carefully rebuilt the sensor with it. It didn’t go in perfectly because it was a bit too large and I didn’t have the exact size wire, but after some careful solder work and some hot glue it should be functional.

Thermistor I removed from the sensor:

Sensor with thermistor from ATC head:

3D model of my mounting boss design:
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 #379280  by remi
Hi Steeve,

I don't know if this will help but anyway... The 1999 or 2000 ATC I have has a custom Motorola MCU, MC68HC05 based. The VFD driver is indeed an OKI chip, a MSM5267B-15 to be accurate. It's a 33 channels driver, although the VFD only uses 25 channels IIRC. I haven't checked if it is relying on the OKI chip to drive the two amber leds on the side of the switches...
Anyway the OKI chip is a basic shift register. The logic analyzer confirmed it's working on 33 bits per word, there's a data line, clock, and a latch. I don't think the "blank" is even used. I have identified the VFD pinout and VFD to OKI wiring but the logic analyzer does't correlate to my findings so... more work required.

I'm stunned by this project, this is great work! Keep it up :)
 #379344  by 00R/T
Thanks for the update, Remi. The more we know about the guts of these systems the better!

I apologize for my lack of updates, but it’s due to a lack of progress. The bare PCBs that are going to go into the ATC head arrived a few weeks ago as did the components for them. However, I’ve been really busy with spring chores around the house and just haven’t had the time to sit down with them yet. It’s going to be quite a bit trickier to test this part because the head won’t run without being in the car. Hopefully it works straight away and I won’t have any debugging to do, but I’ve been doing this long enough to know how unlikely that is!
Sigmaz liked this
 #385671  by Sigmaz
I have the same radio on my bench right now and I've been trying to get it to wake up ..
I wasn't able to sniff the donor bus for the acc / run messages nor the VIN message wrapper id.
Are you able to share your findings? I'd really appreciate it.
thanks man
 #385688  by Sigmaz
I’ve tried to sniff a bit from a friends ‘14 Cherokee but only from the obd port. I see various 205 id’s when the key is inserted and turned. I have tried to send them to the radio.. it’s still not happy.
I assume the id’s on the IHS are probably different. ..
This stinks...
Would you be willing to send me the ID’s you used to power on?
I realize I’ll need to do some vin fiddling, but having the ids would be awesome.

 #390260  by brandonh8403
Amazing work!! I have read many threads on FCA can bus and I find yours most relevant to what I am hoping to do. Your input would be greatly appreciated. I have a 16 Jeep cherokee with the Harman 8.4. I would like to add more cameras than just reverse, here is what i am thinking.
have events trigger the radio to display the reverse camera ( reverse, left turn signal, right turn signal, slow to stop, manual backup camera button)
depending on which event is triggered would also determine what cameras feed is displayed.

how complicated do you think something like this would be to build off the settup you have already created?
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 #390261  by In-trepid
Steve, I was just thinking about this project the other day and wondering what ever happened with it. Having seen it in person and your command of what needed to be done to make it work totally intrigued me. Can we get an update?
 #390374  by 00R/T
In-trepid wrote:Steve, I was just thinking about this project the other day and wondering what ever happened with it. Having seen it in person and your command of what needed to be done to make it work totally intrigued me. Can we get an update?
Honestly, after the Special became driveway art I kind of abandoned it. But, it was nearly complete. I just never finished the HVAC control portion. I would like to revisit it, though, especially if I get the brake lines done.
TrepKing95 liked this