Power interrupted when brake pedal pressed after initial startup

[EvTek23]

I'd wondered why when I sat in the car, set the heated seats to low and steering wheel heat on and then started off, I found that the seats and steering wheel weren't heating up.
When I rechecked the HVAC screen they were all off.
In much the same way as @MikeM found that the accessory socket gets a power interruption when the brake pedal is pressed after you initially sit in the car and the systems turn on, then so to do the heated seats and steering wheel.
I only noticed this because I'd left the HVAC screen displayed, set the items and then pressed the brake pedal to engage drive. Immediately with other relays clicking as they always do at this point, the red third (low) of the seating icon and the heat in red radiating from the wheel icon all went off.
So I will remember next time to set them after selecting D to save them having to be set twice.
Anyone else noticed this on their Trophy model, or if its a quirk of only the MG4, but exists in the MG S5 as well?

 

[Kenno]

Have to say I always press the brake pedal the moment I get in, so that power will start flowing from the high voltage battery to the 12 volt (when it bongs and shows ready). Then all the power hungry devices are not coming straight from the 12 volt. Therefore haven't noticed the above

 

[Coulomb]

Maybe it depends on firmware, but my MG4 extended range (LR here) starts the air conditioning as soon as "bum on seat" is detected (I always leave the HVAC on). That requires the HV battery, so the contactors are on, and the 12 V battery is being charged by the DC-DC. I can see at least 13.8 V on the 12 V battery before I go to full ready with the "hoof on brake".

I do notice that there is a very brief interruption when the car goes to full ready. I assume that this is because the motor controller capacitors are being pre-charged, and this takes a pulse of power from the main battery. Maybe the DC-DC goes off briefly then too, though I don't see why. I can't recall exactly what gets interrupted, but it's noticeable if I pay attention.

 

[Martinonline]

@EvTek23, I, too, discovered this issue yesterday with my MY23 Trophy. I can't remember that the HVAC suffers from the same issue.

 

[bobs2293]

I have similar issues. My dash cam is wired into the cigeratte lighter. Get in the car and sit down it powers up normally. Press the brake peddle the power is briefly interrupted and it shuts down. I just have to reseat it and it comes alive again

 

[EvTek23]

I think it's what they call a "feature" of the way the car fully boots up when you press the brake pedal. Why MG decide to do it this way I'm not sure, but they must have their reasons.
I just hadn't twigged that's why I kept on finding the heated seats and steering wheel off when I'd switched them on.

 

[tsedge]

Mine does the same. It is really annoying, especially if I forget and set up the AC/seats/wheel before I hit the brake pedal.

It is a silly way of doing things and as has been observed above, it isn't about the HV battery per se (because the AC can run anyway), it is about MG's choices with the way the software initialised. It shouldn't require re-entering selections that have already been running.

 

[gary333]

Same here with the resetting of seat and steering wheel heater. However, I'm used to it (as always use heated steering wheel and other half likes seat baking seemingly whatever the weather). The AC does get interrupted when started-up for a split second (you'll hear a change in tone but not fully off as not enough time for fans to spin down).

 

[Anon70]

You will also notice that if you are on the MG Pilot screens not all of the sensor systems activate with just a bum on seat, you have to activate the brake pedal to turn everything on. For example you cannot disable the lane keep assist until the brake pedal has been pressed.

I guess if you want to think of it old school it's like the accessory and on positions for a key in an old ICE car

 

[Panther]

This is good to know, as with my current car I always turn the heated seat and steering wheel on as soon as I get in, and then hit the brake before putting into drive.