A Genius Bar tech phoned to say that the Macbook passed all the external diagnostics so they were going to revert it to factory defaults by loading the firmware and MacOS from another Mac to be confident that everything was as it should be. The tech was sure that this would resolve the issue and that the fans starting randomly when the machine was not under load was typical behaviour. They didn't like me challenging that assertion by saying that in the 18+ months I've owned it, I've only ever had the fans come on at an audible level when processing 8K video. I suppose that the fans might have come on at a level that I couldn't hear them, but certainly not making the noise that they produced with this fault.
Next day, the same tech phoned to say that they'd reloaded firmware and OS and had just created a test logon when the fans came on full bore when the machine was idle. They ran for long enough that the tech managed to start activity monitor to confirm the machine was barely ticking over. They apologised that they'd had the machine for a week and were now predicting another week while they wait for parts to arrive and repairs to be effected. They're swapping out the logic board as their best bet for fixing the problem. I said that the gas gauge sensor was on the battery management daughterboard, but the tech said they'd nothing to indicate the sensor was faulty and second level support had advised swapping the logic board. I emailed them https://www.reddit.com/r/mac/comments/xw7dty/battery_gas_gauge_sensor_not_producing_a_reading/ in addition to the link in my original post but no reply. So, looks like they're going to replace the £1,200 thing then have to clear and re-associate the Secure Enclave, rather than just clean the sensor first to see if that resolves the issue. I don't know if the battery management daughterboard is fixed to the logic board, or if it's separate, although I found a 'flexible link cable' for connecting the battery management unit to the logic board on Intel MacBooks, indicating it was separate in Intel times.
I suppose the replacement logic board might fix it if the problem really isn't anything to do with the gas gauge sensor, but I've a funny feeling I'm going to get the machine back after two weeks with the fault still present. I guess that the tech might 'accidentally' clean the sensor while working on the machine.
I'll update again in due course.
Cheers,
Bill
