A/C not blowing air and heated seats not working

[svinorenko]

The A/C panel buttons work, they change the parameters of A/C, also seat heating buttons change the intensity of heating, but A/C does not blow any air and seats are not heated at all.
No pre-symptoms, I drove normally with A/C, parked the car, 2 hours later when I get back to it, A/C won't work anymore.
OBD scanner show multiple errors, erasing them only left me with one non-erasable: E70C2D (AC-LIN-1: Fan output stage does not answer, bus error fan output stage.). Even though the error indicates that the blower motor is dead, I don't think so, cause why seats heating broke at the same time?

Car is almost new, 3000 km.
I did disassemble the center console and took out A/C head unit like a month ago, but I'm sure I connected it back properly and it was working for the whole month after. Also when I turn A/C ON / OFF, I can hear the clicking noise under the dash, so there is definitely a connection between the head unit and the car.

Also when I try to start the auxiliary ventilation, it will turn on the A/C display, will not start the A/C itself, and in around 15 seconds it will shut off and give me an error:

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[Khain]

The A/C panel buttons work, they change the parameters of A/C, also seat heating buttons change the intensity of heating, but A/C does not blow any air and seats are not heated at all.
No pre-symptoms, I drove normally with A/C, parked the car, 2 hours later when I get back to it, A/C won't work anymore.
OBD scanner show multiple errors, erasing them only left me with one non-erasable: E70C2D (AC-LIN-1: Fan output stage does not answer, bus error fan output stage.). Even though the error indicates that the blower motor is dead, I don't think so, cause why seats heating broke at the same time?

Car is almost new, 3000 km.
I did disassemble the center console and took out A/C head unit like a month ago, but I'm sure I connected it back properly and it was working for the whole month after. Also when I turn A/C ON / OFF, I can hear the clicking noise under the dash, so there is definitely a connection between the head unit and the car.

Also when I try to start the auxiliary ventilation, it will turn on the A/C display, will not start the A/C itself, and in around 15 seconds it will shut off and give me an error:

The persistent E70C2D LIN bus error points directly to a total communication failure on the AC-LIN-1 sub-bus, which controls the blower fan output stage and power management for related cabin comfort modules like seat heating. Since your center console work was a month ago, the shared fuse, a loose main connector pin at the IHKA/A/C module, or a shorted blower regulator is likely dragging down the entire LIN line.

 

[svinorenko]

The persistent E70C2D LIN bus error points directly to a total communication failure on the AC-LIN-1 sub-bus, which controls the blower fan output stage and power management for related cabin comfort modules like seat heating. Since your center console work was a month ago, the shared fuse, a loose main connector pin at the IHKA/A/C module, or a shorted blower regulator is likely dragging down the entire LIN line.

Thanx, that fits well with the symptoms. Is the fuse is the regular fuse box in the trunk? Blower regulator is the blower controller which is inside the blower motor unit itself?
Should I try to open up the central console again to check all the connectors first?

 

[26StratMT]

Not an expert here but I would start with the easy stuff first.
Check fuses.
If the easy stuff fails something you did in the console would be next suspect.
Check all connectors, check for pinched or chaffed wires, etc.
Good luck!

 

[concept]

Some of this may help:


Given that the A/C blower and both heated seats failed at exactly the same time, I would actually be less suspicious of the blower motor itself and more suspicious of a shared power, LIN-bus, or HVAC control issue.
The fault code is very telling:

E70C2D: AC-LIN-1: Fan output stage does not answer, bus error fan output stage. [f30.bimmerpost.com], [bimmerfest.com]

On BMW-based platforms (and the A90 Supra is largely BMW electronics), this code usually means the IHKA/HVAC module cannot communicate with the blower's electronic regulator/output stage over the LIN bus. BMW technicians frequently investigate the LIN wiring, power supply, ground, or the blower output stage itself when this code appears. [f30.bimmerpost.com], [bimmerfest.com]
Why the heated seats matter
Your observation is valid:

• HVAC controls still respond on the screen.
• Seat-heater level indicators change normally.
• No blower operation.
• Heated seats produce no heat.

That suggests the user interface is working, but the system is not actually driving the loads.
A few possibilities stand out:
1. Blower output stage/regulator lost power
The blower motor on these cars uses an integrated electronic controller ("fan output stage" / FSU). If its power supply or ground disappears, the HVAC module sees exactly the type of LIN communication fault you're getting. [go-parts.com], [f30.bimmerpost.com]
Since the car is nearly new, a failed power feed, connector, or fuse is arguably more likely than a worn blower motor.
2. Shared fuse or power distribution issue
Many BMW systems disable comfort functions when a shared supply is missing. If the heated seats and HVAC blower share a fuse block, relay, or power distribution module, both symptoms could appear together.
I'd check every fuse related to:

• IHKA (climate control)
• Blower motor
• Seat heating
• Front electronics/body controller

even if they look unrelated.
3. LIN-bus communication fault
The code literally reports a LIN communication problem. [f30.bimmerpost.com], [bimmerfest.com]
A damaged connector, pin not fully seated, water intrusion, or wiring issue between the HVAC module and blower output stage could cause:

• blower disabled
• auxiliary ventilation failure
• secondary HVAC-related functions not operating correctly

4. Connector issue from prior disassembly
You mentioned removing the HVAC head unit a month ago.
I agree it seems unlikely because it worked for a month afterward, but I'd still recheck:

• HVAC control panel connectors
• Any connector behind the center stack that carries LIN communications
• Pins pushed back in the connector housing

A partially seated connector can work for weeks and then fail after vibration.
The auxiliary ventilation message
The message:

"Heating/cooling deactivated so as to restrict the vehicle's starting ability..."

may be a consequence rather than the cause.
If the car cannot communicate with the blower output stage, auxiliary ventilation cannot operate, so the system aborts the request.
What I would do next

1. Check all HVAC and heated-seat related fuses with a meter, not just visually.
2. Inspect the blower motor/output stage connector in the passenger footwell.
3. Verify power and ground at the blower output stage.
4. Look for LIN-bus wiring damage between the blower output stage and IHKA.
5. Since the car has only 3,000 km, strongly consider a warranty visit before replacing parts.

My current suspicion ranking would be:

1. Blower output stage/regulator power loss or failure
2. Fuse/power distribution issue affecting multiple comfort systems
3. LIN-bus wiring/connector fault
4. HVAC control module issue
5. Actual blower motor failure

The fact that the heated seats quit simultaneously is the strongest clue that this is probably not just a worn-out blower motor.

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