Need help understanding HVAC module requirements - 3rd gen Ram with 4th gen Android head unit/Dash swap

[gmax111]

Hey everyone,


I'm working on an interesting project with my 2004 Ram (3rd gen). I've already completed a full interior and dash swap, and now I'm installing an Android head unit that has digital HVAC controls. Here's my situation:


Current Setup:

• 2004 Dodge Ram
• Android head unit designed for 4th gen Ram manual HVAC controls
• All 3rd gen HVAC components (I've mapped out the wiring compatibility between 3rd and 4th gen)

Issue:The HVAC controls are grayed out on the head unit. I have everything connected on the C1 and C2 HVAC plugs except for the CAN_IHS +/- wires (pins 23&24), since my 3rd gen doesn't have CANBUS.


My Theory:I think I need an HVAC module to send activation messages to the head unit about actuator states and fan speed. I'm planning to grab one from a wrecker to test this. I'm also half decent with CANBUS networks but not too specific to Dodge/Chrysler. My original thought was that the manual controls wouldn't need CANBUS but now that I'm understanding what the head unit is trying to do I believe it needs the IHS network to initialize.


My Question: Does anyone know if the HVAC module needs initialization messages from the ECU or BCM to function? Or does it just need power (either constant or ignition)?

 

[SitKneelBend]

Hey everyone,


I'm working on an interesting project with my 2004 Ram (3rd gen). I've already completed a full interior and dash swap, and now I'm installing an Android head unit that has digital HVAC controls. Here's my situation:


Current Setup:

• 2004 Dodge Ram
• Android head unit designed for 4th gen Ram manual HVAC controls
• All 3rd gen HVAC components (I've mapped out the wiring compatibility between 3rd and 4th gen)

Issue:The HVAC controls are grayed out on the head unit. I have everything connected on the C1 and C2 HVAC plugs except for the CAN_IHS +/- wires (pins 23&24), since my 3rd gen doesn't have CANBUS.


My Theory:I think I need an HVAC module to send activation messages to the head unit about actuator states and fan speed. I'm planning to grab one from a wrecker to test this. I'm also half decent with CANBUS networks but not too specific to Dodge/Chrysler. My original thought was that the manual controls wouldn't need CANBUS but now that I'm understanding what the head unit is trying to do I believe it needs the IHS network to initialize.


My Question: Does anyone know if the HVAC module needs initialization messages from the ECU or BCM to function? Or does it just need power (either constant or ignition)?

I don't know the answer to your specific question about initialization (which I think would come form the BCM) but you are on the right track and the reason it doesn't work is that the android radio will send all of those messages or CANBUS. Furthermore, the "manual" HVAC controls of the lower trim vehicles have the HVAC module integrated in the HVAC bezel itself and the higher trim vehicles that come with 8.4" screens have a separate remote HVAC module located on the passenger side at the very top of the floor kick panel area almost in line with the glove box.

Do you have any pictures of your swap so we can see what you're working with?

 

[gmax111]

I don't know the answer to your specific question about initialization (which I think would come form the BCM) but you are on the right track and the reason it doesn't work is that the android radio will send all of those messages or CANBUS. Furthermore, the "manual" HVAC controls of the lower trim vehicles have the HVAC module integrated in the HVAC bezel itself and the higher trim vehicles that come with 8.4" screens have a separate remote HVAC module located on the passenger side at the very top of the floor kick panel area almost in line with the glove box.

Do you have any pictures of your swap so we can see what you're working with?

Good call on the pics and some further information. I searched the local wreckers for a 2014 limited ram by using the body code for the limited model. I pulled pretty much the entire interior from the truck I found. My airbox in the 3rd gen had to be modified to adapt to 4th gen air ducts, and my column shifter had to be cut and extended 0.5inch. There was a bit of trimming that needed to be done around where the A pillars fit with the dash but the dash was nearly direct fit.

For the steering wheel I had to take apart the cruise control/button modules and rework the board. I cut and remade traces and resoldered resistors to match what my 3rd gen was looking for on the signal wires for cruise control and various buttons. I did the same thing for the headlight switch (although my dimmer still needs some work). I may make a full PCB design and send it off to be made for the steering wheel controls and the headlight switch. I may sell these for other people looking to do the swap.
Next I will be swapping late model 3rd gen door panels painted black to match the dash, and I want to redo my headliner with black suede.

I don't know the answer to your specific question about initialization (which I think would come form the BCM) but you are on the right track and the reason it doesn't work is that the android radio will send all of those messages or CANBUS. Furthermore, the "manual" HVAC controls of the lower trim vehicles have the HVAC module integrated in the HVAC bezel itself and the higher trim vehicles that come with 8.4" screens have a separate remote HVAC module located on the passenger side at the very top of the floor kick panel area almost in line with the glove box.

Do you have any pictures of your swap so we can see what you're working with?

You make an interesting point about the integrated HVAC module. The manual controls arrive today for testing, and I now understand why I couldn't find a standalone HVAC module at the wreckers - I was searching based on my incorrect assumption that the manual controls used the separate module on the right side of the dash. Your point also has me thinking: could the system work by just connecting the manual controls behind the dash using CAN_IHS (Hi/Low) to create a network with the head unit, along with basic power and ground? I'll double check this as well.

Here is the 14.4" screen for those that are curious, the second pic is my head unit and you can see the HVAC controls are grayed out, swapping canbus protocol on the head unit to various vehicle models hasn't enabled them either.


If it's just initialization the head unit is seeking then I can record the CANBUS messages and develop an esp32 with a can-hat to satisfy the head unit. The head unit might need real-time HVAC actuator and fan status updates beyond initialization, but we shall see. I would also share my 3rd gen to 4th gen android head unit and harness pinouts once I've completed the project.

I bought the head unit from Alibaba, which came with a pre-made harness designed for 4th gen Rams. While I can understand most connections using available 4th gen wiring diagrams, there's one specific HVAC connector that goes between the audio portion of the head unit to the HVAC portion whose wiring details remain unclear. The seller provided limited documentation as the system is usually plug and play. I'm trying to speak to an engineer but the language barrier is rough.

Anyway, I hope this provides further interest and others might have more information or clues to help with this.

One other thing I'm concerned about is if the stand alone HVAC module needs init messages like vin and vehicle specific checks. I've seen on other posts that people who have used salvaged HVAC modules, they needed to be re-programmed to their truck, and I've seen some posts that say it just worked after replacement.

 

[SitKneelBend]

View attachment 557821View attachment 557814View attachment 557822View attachment 557815View attachment 557816View attachment 557817View attachment 557818

Good call on the pics and some further information. I searched the local wreckers for a 2014 limited ram by using the body code for the limited model. I pulled pretty much the entire interior from the truck I found. My airbox in the 3rd gen had to be modified to adapt to 4th gen air ducts, and my column shifter had to be cut and extended 0.5inch. There was a bit of trimming that needed to be done around where the A pillars fit with the dash but the dash was nearly direct fit.

For the steering wheel I had to take apart the cruise control/button modules and rework the board. I cut and remade traces and resoldered resistors to match what my 3rd gen was looking for on the signal wires for cruise control and various buttons. I did the same thing for the headlight switch (although my dimmer still needs some work). I may make a full PCB design and send it off to be made for the steering wheel controls and the headlight switch. I may sell these for other people looking to do the swap.
Next I will be swapping late model 3rd gen door panels painted black to match the dash, and I want to redo my headliner with black suede.


You make an interesting point about the integrated HVAC module. The manual controls arrive today for testing, and I now understand why I couldn't find a standalone HVAC module at the wreckers - I was searching based on my incorrect assumption that the manual controls used the separate module on the right side of the dash. Your point also has me thinking: could the system work by just connecting the manual controls behind the dash using CAN_IHS (Hi/Low) to create a network with the head unit, along with basic power and ground? I'll double check this as well.

Here is the 14.4" screen for those that are curious, the second pic is my head unit and you can see the HVAC controls are grayed out, swapping canbus protocol on the head unit to various vehicle models hasn't enabled them either.
View attachment 557819View attachment 557820

If it's just initialization the head unit is seeking then I can record the CANBUS messages and develop an esp32 with a can-hat to satisfy the head unit. The head unit might need real-time HVAC actuator and fan status updates beyond initialization, but we shall see. I would also share my 3rd gen to 4th gen android head unit and harness pinouts once I've completed the project.

I bought the head unit from Alibaba, which came with a pre-made harness designed for 4th gen Rams. While I can understand most connections using available 4th gen wiring diagrams, there's one specific HVAC connector that goes between the audio portion of the head unit to the HVAC portion whose wiring details remain unclear. The seller provided limited documentation as the system is usually plug and play. I'm trying to speak to an engineer but the language barrier is rough.

Anyway, I hope this provides further interest and others might have more information or clues to help with this.

One other thing I'm concerned about is if the stand alone HVAC module needs init messages like vin and vehicle specific checks. I've seen on other posts that people who have used salvaged HVAC modules, they needed to be re-programmed to their truck, and I've seen some posts that say it just worked after replacement.

I see you're a mad lad! What a conversion! Beautiful Truck!

To be clear, the bezel you have for HVAC controls in your picture is the bezel that has the remote HVAC module on the passenger side in 4th gen trucks. SO for that bezel to ever work, it would need the remote HVAC module to receive commands (at the least).

I haven't messed with those Tesla style radios in years and it looks like they have come a long way, but they used to have an external CANBUS module that would interface with the trucks CANBUS in order to send commands for HVAC controls and programmed options that would be activated from the radio.

 

[gmax111]

I see you're a mad lad! What a conversion! Beautiful Truck!

To be clear, the bezel you have for HVAC controls in your picture is the bezel that has the remote HVAC module on the passenger side in 4th gen trucks. SO for that bezel to ever work, it would need the remote HVAC module to receive commands (at the least).

I haven't messed with those Tesla style radios in years and it looks like they have come a long way, but they used to have an external CANBUS module that would interface with the trucks CANBUS in order to send commands for HVAC controls and programmed options that would be activated from the radio.

Haha thanks! You could say I'm more autistic than mad for attempting this but either way, lmao. I'd like to give back to the community with modification addictions like I have

And yeah the controls in the above picture were just what came on the truck I pulled the bezel from. I knew right away those wouldn't work with my 3rd gen airbox without full canbus modules and sensors communicating properly. I'm glad you pointed out the operation of the HVAC Module with what control systems.

This is the HVAC Controls from a 3rd gen:

Front has 4 speed fan selector


Rear plugs, (Right) has 5 pins for fan speed, (Left) is controls for mixing/flap actuator positions (as well as evap sensor, lamps, etc)



4th Gen Manual controls (typically found in base model 2500/3500's):

Front has 4 speed fan selector (Same selections on front as 3rd gen)


Rear plugs, (Right) has 5 pins for fan speed, (Left) is controls for mixing/flap actuator positions (evap sensor, lamps, etc) as well as CAN_IHS(+/-). What's interesting is the manual controls actually control the AUTO Headlight function from the sun sensor on the dash. 3rd Gens don't natively have AUTO Headlights but now with the dash swap it is possible to add it.


Nearly all the connections needed for the 3rd gen airbox are present on the 4th gen Manual A/C Controls. I believe when I connect the 4th gen manual controls, it should operate the Fan and Airbox actuators in my truck as I have wired.

I ordered the Android head unit optioned for manual controls thinking the head unit would operate the airbox on analog signals just like the controls do. Now here I am scratching my head as to if my wiring is correct or if there's missing CAN messages. I may tear apart this 4th gen controls box to see what the PCB is doing.

 

[SitKneelBend]

If you haven't already looked here, this site is a great resource for factory wiring purposes.

Mopar Connection Repair Kit

connectorrepairkit.mopar.com

Use the source truck's info to setup the search...

 

[04fxdwgi]

Haha thanks! You could say I'm more autistic than mad for attempting this but either way, lmao. I'd like to give back to the community with modification addictions like I have

And yeah the controls in the above picture were just what came on the truck I pulled the bezel from. I knew right away those wouldn't work with my 3rd gen airbox without full canbus modules and sensors communicating properly. I'm glad you pointed out the operation of the HVAC Module with what control systems.

This is the HVAC from a 3rd gen:

Front has 4 speed fan selector
View attachment 557826

Rear plugs, (Right) has 5 pins for fan speed, (Left) is controls for mixing/flap actuator positions (as well as evap sensor, lamps, etc)
View attachment 557827


4th Gen Manual controls (typically found in base model 2500/3500's):

Front has 4 speed fan selector (Same selections on front as 3rd gen)
View attachment 557828

Rear plugs, (Right) has 5 pins for fan speed, (Left) is controls for mixing/flap actuator positions (evap sensor, lamps, etc) as well as CAN_IHS(+/-). What's interesting is the manual controls actually control the AUTO Headlight function from the sun sensor on the dash. 3rd Gens don't natively have AUTO Headlights but now with the dash swap it is possible to add it.
View attachment 557829

Nearly all the connections needed for the 3rd gen airbox are present on the 4th gen Manual A/C Controls. I believe when I connect the 4th gen manual controls, it should operate the Fan and Airbox actuators in my truck as I have wired.

I ordered the Android head unit optioned for manual controls thinking the head unit would operate the airbox on analog signals just like the controls do. Now here I am scratching my head as to if my wiring is correct or if there's missing CAN messages. I may tear apart this 4th gen controls box to see what the PCB is doing.

4th Gen can bus changed in '14, I believe and won't talk to the earlier stuff. Gen 3 was earlier than that.

Pins might be there, but talk a different language.

 

[gmax111]

4th Gen can bus changed in '14, I believe and won't talk to the earlier stuff. Gen 3 was earlier than that.

Pins might be there, but talk a different language.

Yeah I'm aware of this part. But CAN_IHS that was introduced in 2010 remains nearly the same and same data rate. ID's may change from year to year or based on model changes and network changes between models (this is unknown to me). From what I can tell most parts/modules seem to be interchangeable, and even the HVAC module from 2018+ Ram classic looks identical to 2014-2018 HVAC module (different part numbers).

More information for others:
2002-2003: ISO 9141-2 protocol (Chrysler's version of CAN)

2004-2005: Transition period

• Some models: ISO 9141-2
• Others: Early CAN bus implementation

2006-present: Full CAN bus (Controller Area Network)

• 2006-2009: CAN 2.0A/B
• 2010+: Enhanced CAN with additional modules and higher data rates
• 2019+: Includes FCA's newer PCI architecture alongside CAN

2010-2013 Dodge Ram used CAN bus with a data rate of 500 kbps, with the main communication happening over 2 CAN networks:

• CAN-C (powertrain, ABS)
• CAN-IHS (Interior/Exterior lighting, HVAC)

2014-2018 models upgraded to:

• Higher data rate (1 Mbps on CAN-C)
• Added CAN-B network for body control modules
• Enhanced diagnostic capabilities through expanded Parameter IDs (PIDs)
• Introduction of LIN bus for low-speed device control

 

[SitKneelBend]

4th Gen can bus changed in '14, I believe and won't talk to the earlier stuff. Gen 3 was earlier than that.

Pins might be there, but talk a different language.

I think he's aiming to program his own interface if I'm understanding his approach correctly and only for limited functions. At first glance, I'm thinking "maybe?"

I'm wondering if some "heavy hitters" could weigh in on this too like @Mpgrimm2 ,@Jimmy07 or @Roman217 might be able to chime in (sorry if I missed anyone, I know there are a lot of folks here with knowledge, just thinking the mod-makers might have some insight here)

 

[gmax111]

If you haven't already looked here, this site is a great resource for factory wiring purposes.

Mopar Connection Repair Kit

connectorrepairkit.mopar.com

Use the source trucks info to setup the search...

This is super useful! I was looking for needed connectors in the wreckers because I couldn't find an online resource or part number for them!!

Also has the pinouts!!


Edit to add: With the wiring diagrams and these pinouts, you can feed AI (chatgpt, claude) this information and nearly build any harness you need.

 

[nighttrain]

Wow I can't believe someone is figuring this out. I just did a longhorn swap over the holidays and have the 3rd get heater controls zip tied in place for now. I will defiantly order one of these screens if @gmax111 can make the heat turn on. Any updates?

How are you getting the instrument cluster under the touch screen to work?

 

[gmax111]

I'm trying but I really think this won't be for the faint at heart. I connected the 4th gen manual HVAC controls to my truck and I can get almost everything to work except to command the A/C compressor to engage the clutch (more on this below).

I had to order a chip to communicate on the 3rd gen J1850 bus as well as a chip to communicate on the CAN_IHS network of the android headunit. These would connect to an esp32 to handle some simple programming.

The 3rd gen uses the ECM to command the AC compressor to turn on/off after it checks relevant sensors report good standing. The headunit needs activation messages to enable HVAC controls on the screen. So I will have to handle this part using programming on the esp32, which isn't hard once I can decode the messages on both platforms. I'm pretty sure the 3rd gen J1850 messages are well known and reported on the internet, I have a starting point for these in my notes.

I have to log and decode the 4th gen messages so I will be borrowing a friends 4th gen to monitor CAN_IHS messages for the activation messages. I see benchtop emulators on eBay for the uConnect stereo's ($100-$150) and I'm actually wondering if these are just feeding a recorded series of messages to the units to activate head units while on a benchtop. So basically this part has been done before and I'm sure someone here has more information.

 

[gmax111]

One other thing to add is that I may 3d model a bezel to 3d printed for my 3rd gen HVAC controls for now. I'm driving my truck around without HVAC right now and it sucks, my truck is also looking like it's stolen at the moment

If I make this I can drop the 3d model on the internet for other people to have printed so we don't just have HVAC controls hanging out of our dash haha

 

[nighttrain]

One other thing to add is that I may 3d model a bezel to 3d printed for my 3rd gen HVAC controls for now. I'm driving my truck around without HVAC right now and it sucks, my truck is also looking like it's stolen at the moment

If I make this I can drop the 3d model on the internet for other people to have printed so we don't just have HVAC controls hanging out of our dash haha

I'll post a pic tomorrow of the heater consoles, that sounds like too much effort for a temporary solution. I know nothing about programming so it sounds like making the heater controls work off the head unit would be far too complicated for me. I could move the heater controller into the centre console so I could fit the 14" head unit though.

Does the head unit have the capability to run the heated/cooled seats? Or are we running into the same problem where the head unit needs to talk to the bcm and from the bcm to the seat module? I assume you aren't using the 4th gen bcm.

 

[nighttrain]

4WD
I am trying to make the 4g 4wd switch work but it has 3 wire terminals instead of 6 like my 3g switch. Was starting to think it was impossible because of the can bus situation, but I see you figured it out. Any guidance would be appreciated.


INSTRUMENT panel
I would like to order an instrument panel that has the 5 accessory buttons so I can put a relay box under the hood to run light bars, strobes, back up lights etc. I have the standard heated seats buttons and again only 3 wire terminals so I assume those buttons send signals not voltage.