Digital HVAC upgrade breaks locking differential. Warning!

[hobbymaster001]

Of the mods I have done on my truck most were very minor... bed liner, hood deflector, homelink mirror, etc. One bigger one that I did was buy an identical dual zone HVAC control from a 2022 Ford Escape. Unplugged the old one, swapped out the button with the truck image on it so it matched the vehicle, plugged it in, and flashed the as built codes to it. Everything seemed to work perfectly and I have been LOVING it ever since it was installed.

I have had this working for well over 8 months now without issue, but I noticed when offroading recently that I got stuck in mud and it didn't seem like my diff was locking at that time. After a bunch of effort to get out a friend was able to verify wheel slip and the diff not appearing to lock. Brought it in for the turn signal recall and had them diagnose that while it was in the shop. After extensive testing they determined the HVAC module was the culprit. Didn't believe it myself, but the new (original design, non digital) HVAC module came in, they installed, flashed it and everything is 100% working fine now.

Truck configuration: 2023 Ford Maverick Tremor Lariat Luxury with CoPilot 360.

Has anyone else noticed this behavior? If so, did you find a workaround for it?

If I find a dual zone digital module again in the future (maybe off of something known to have a licking rear diff) I may try this one more time being aware of this issue. I may try to solder the ribbon cable connectors from one with the digital displays onto my original one (I kept it for spare buttons etc just in case) if I dont have luck with the other idea and do a bit more experimentation. I am still floored that the locking diff needs to interact with the climate module, and am happy to have that function back but man am I going to miss the digital temperature readouts.

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[Robber's Roost]

When I did this with my '24 Lariat AWD ecoboost there was no flashing of the module needed. Just plug and play. Did you use an HVAC module from an escape with the same drivetrain, as in not from an escape hybrid? They look the same but they're not.

 

[hobbymaster001]

I flashed mine because it has a vin field that could be updated. It did work without it but I wanted as builts on it so Ford could never complain because it's their own hardware and settings.

And as far as the vehicle the ad is down now so I can't get details but the buttons were identical and when I had looked it up it was a high end st trim and was a gas vehicle not hybrid. Those don't have lockers on them so maybe that is the difference. Does yours have the diff lock option and does that still work for you after the swap? Literally everything worked perfectly for me with the exception of the diff locker.

 

[EONR24]

I flashed mine because it has a vin field that could be updated. It did work without it but I wanted as builts on it so Ford could never complain because it's their own hardware and settings.

And as far as the vehicle the ad is down now so I can't get details but the buttons were identical and when I had looked it up it was a high end st trim and was a gas vehicle not hybrid. Those don't have lockers on them so maybe that is the difference. Does yours have the diff lock option and does that still work for you after the swap? Literally everything worked perfectly for me with the exception of the diff locker.

To activate the locking rear diff, don't you need to engage it with a button? It also says it engages only under certain drive modes.

The drive mode button and auto stop start button and several others are all included in the HVAC coding. I know this because I was able disable or enable these buttons through HVAC coding in FORSCAN.

So, My theory is something in the HVAC coding was not right specifically for your Tremor. The Tremor may use a unique coding or button or wiring because of the Locking Rear diff. Aren't the tremors buttons even in a different location than non tremors?

 

[EONR24]

Send me your current HVAC as built codes. Ill compared them with mine on an XL ecoboost.

Here are a few codings that could affect it

 

[hobbymaster001]

To activate the locking rear diff, don't you need to engage it with a button? It also says it engages only under certain drive modes.

The drive mode button and auto stop start button and several others are all included in the HVAC coding. I know this because I was able disable or enable these buttons through HVAC coding in FORSCAN.

So, My theory is something in the HVAC coding was not right specifically for your Tremor. The Tremor may use a unique coding or button or wiring because of the Locking Rear diff. Aren't the tremors buttons even in a different location than non tremors?

Yes that is correct, there is a button in the cluster of 6 of them in front of the center console storage indentation near the auto brake hold, drive mode, AWD etc buttons. Turning on the sand drive mode also locks the diff. Everything except the locker functioned after swapping the HVAC unit until they replaced it. Even after I flashed my as builts to it. I did notice that the I believe all of the buttons are in the same place, they just have a different number of buttons. Like the cruise control on the wheel, same place, same shape, just more buttons of you have copilot 360 assist vs just copilot 360

 

[hobbymaster001]

I can't seem to be able to get my phone to do anything with the AB file I have on my cloud storage. I'll send the HVAC specific as builts tomorrow morning.

As a note... My HVAC module showed a different part number obviously because the displays etc were different... But there was HW 3.0 on it... Mine was HW 3.1. the problem module also showed sw 7.0.0 on it and mine was 5.x.x whatever that was. I am assuming if I find matching hw values that sw is software and that can be updated maybe ... Any idea what those values are if it's not the hardware revision and software revision as flashed from the factory, and what may have changed?

 

[EONR24]

Yes that is correct, there is a button in the cluster of 6 of them in front of the center console storage indentation near the auto brake hold, drive mode, AWD etc buttons. Turning on the sand drive mode also locks the diff. Everything except the locker functioned after swapping the HVAC unit until they replaced it. Even after I flashed my as builts to it. I did notice that the I believe all of the buttons are in the same place, they just have a different number of buttons. Like the cruise control on the wheel, same place, same shape, just more buttons of you have copilot 360 assist vs just copilot 360

If you flashed your original as builts to the digital HVAC control unit then I would lean toward the unit just being incompatible with tremors and it probably has to do with the wiring differences present due to the rear locking diff.

But yeah it would still be helpful to see if there are any coding differences between the HVAC coding in a tremor like yours vs a XL, XLT, Lariat ecoboost. You can private message me your VIN if you want and I can look at the HVAC coding that way.

Like I said it may not be a coding issue though. The escape units could just be incompatible with the Tremor!

 

[TheShark]

This is interesting, I have an Escape EB HVAC digital readout on my '24 Lariat Tremor and I too flashed the as built codes as well. To be honest I've never had an occasion to use any of the modes or lock the rear end so I have no idea if it works or not. I guess I'll have to give it a try and see.

 

[hobbymaster001]

Alright, LONG overdue update here! I ended up purchasing a 2022 Bronco Sport HVAC cluster. From the outside, the dials are different pattern wise on the grip. They match the pattern on the dial shifter and have the silver accent at the base of the knobs instead of along the dial face.

Bronco unit I have now with the displays:
HW: 3.2
SW: 8.2.3

My new replacement unit straight from Ford that works again has the following:
HW: 3.1
SW: 5.0.1

The unit that I had from the Escape:
HW: 3.0
SW: 7.0.0

The original Unit that came with the truck:
HW: 3.1
SW: 5.x.x (photo is blurry so I am not sure on the last digits)

When I put the bronco unit in it worked out of the box but my diff no longer locked again. I flashed my own as builts back into the unit, and still the same behavior. Absolutely everything works except for the diff once again. Frustrating. Couldn't tell if the Bronco Sport I got this from was a special edition with the locker or just a normal sport where it was optional.

As requested, these are my as builts for the HVAC module:

;Block 1
733G1G10076816B46E4
733G1G25A19E0408050
733G1G366006B5846AD
733G1G40AA06B5846F2
733G1G5721082648028
733G1G6ED0EA0042000
733G1G7FC41D270B071
733G1G80281A0000066
733G1G9000000000044
733G1GA00000000004B
733G1GB00000000004C
733G1GC00000000004D
733G1GD000000004E
;Block 2
733G2G1<vin-chunk-1-redacted>B5
733G2G2<vin-chunk-2-redacted>7C
733G2G3<vin-chunk-3-redacted>6E
733G2G4<vin-chunk-4-redacted>AB

Additionally, I did a whole lot of digging on the PCBs themselves. There are ZERO differences between my original board the truck shipped with (HW 3.2) and the replacement ford put in when fixing the diff issue (HW 3.1). I can see a slight difference in a few LEDs on them so I think they just changed vendors and that is the difference in HW version.

NOW the interesting part... I wasn't able to get the Escape unit back as it was sent back to ford, but I tore down the Bronco one I have. two of the photos here are the factory original part (without the flat cable connectors) and the two other photos with the connectors are the Bronco board. I have highlighted the missing components with yellow.

On the contact side of the board I have accounted for the four missing LEDs and the two missing resistors on the upper left and right banks. Those are for the dial backlights. There is one resistor missing in the upper middle of the board that leads to a VIA that is orphaned on the back so that is for an internal layer I cannot seem to trace. Everything has continuity to it.

On the logic side of the board, there is one large resistor missing upper center. Below that there is one resistor and capacitor missing that are part of a trace that heads into the microcontroller. I have not been able to determine what those do, or what the large resistor does yet. On the far right hand side there is one missing transistor, and below that slightly to the left, there appears to be a ferrite bead or resistor or similar non polarized SMD component that swaps from the pair of pads to the right, and moved left one pad pair on the Bronco unit. I am still trying to trace things out but the multi layer PCB is killing me.

If anyone has a tremor and has the HVAC displays, and their diff lock button works (literally just press it and you'll see the diff lock light on the dash come on), is there any chance I could see a photo of a PCB that is functioning as intended? These boards are so similar and simple (almost everything on the one side is LED related, and the other side is mainly logic and pull up/downs, lighting, and feeds in and out of the controller) that I can't imagine it would be difficult to make this work once I see something functioning.

My current bets are on the large missing resistor or the missing transistor being the culprit. Does anyone have the connector pinouts and what they are labeled for? I would love to trace this back and probe it with a scope!

 

[hobbymaster001]

I am receiving my hot air rework station in today and plan to yank some components off of my factory original board so I can trace leads more effectively. Worst case if I am unable to figure it out, I will set up my original board to match the Bronco one just without the parts to populate for the screens. That way I can see what functions don't work (expecting at least the dial back light LEDs) and hopefully the locker. Then I can work backward and see what actually triggers the locker. I don't have the motivation to tear out the whole dash to get to the locking diff button so I can trace it back through the harness so if anyone has wiring diagrams for the Lariat Lux Tremor I would GREATLY appreciate some data to work with!

Thanks!

 

[TheShark]

I replaced the HVAC controls on my '24 Lariat Tremor with a unit from a '21 Escape with the digital readouts. Everything was working or at least I thought it was, I never in a million years would have thought to check the locking diff but after reading this thread I decided to check. Sure enough, didn't work, the dash light never came on. So I pulled the Escape unit and put the original back in, light came on so I'm assuming it's working now. Switched out the units one more time just to be sure and the same results.

The unit from the Escape:
LJ6T-18C612-GD
HW: 3.0
SW: 8.0.0

The original from the Tremor:
NZ6T-18C612-GE
HW: 3.1
SW: 5.0.1

 

[hobbymaster001]

Excellent to know and I feel better about not being crazy! I have two identical known working PCBs so I think I am going to go straight to pulling components and see which ones end up disabling that function and maybe move them over to the new board. I am literally unable to find a hardware and software version that matches the known working ones that also have the dual screens to give a go. I did see on another thread in here someone posted the OEM part number from a 2022 with the screens but I cannot find it again. I just remember seeing that the part had been discontinued and was replaced by the one without the screens so if someones OEM one has a problem they will be downgraded to what we have without the screens.

Now ... the hard part will be getting diagrams and pinouts because I don't have any friends at the ford garage yet I can pull information from. That would make reverse engineering and making a working unit SO much easier.

 

[TheShark]

Excellent to know and I feel better about not being crazy! I have two identical known working PCBs so I think I am going to go straight to pulling components and see which ones end up disabling that function and maybe move them over to the new board. I am literally unable to find a hardware and software version that matches the known working ones that also have the dual screens to give a go. I did see on another thread in here someone posted the OEM part number from a 2022 with the screens but I cannot find it again. I just remember seeing that the part had been discontinued and was replaced by the one without the screens so if someones OEM one has a problem they will be downgraded to what we have without the screens.

Now ... the hard part will be getting diagrams and pinouts because I don't have any friends at the ford garage yet I can pull information from. That would make reverse engineering and making a working unit SO much easier.

Good luck, I hope you figure it out. For now I'm back to no displays

 

[lavaspill]

I replaced the HVAC controls on my '24 Lariat Tremor with a unit from a '21 Escape with the digital readouts. Everything was working or at least I thought it was, I never in a million years would have thought to check the locking diff but after reading this thread I decided to check. Sure enough, didn't work, the dash light never came on. So I pulled the Escape unit and put the original back in, light came on so I'm assuming it's working now. Switched out the units one more time just to be sure and the same results.

The unit from the Escape:
LJ6T-18C612-GD
HW: 3.0
SW: 8.0.0

The original from the Tremor:
NZ6T-18C612-GE
HW: 3.1
SW: 5.0.1

Is it just the dash light isn’t coming on or it’s not engaging the lock? You should be able to see in the off road screen if all 4 wheels are moving.

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