Understanding how the interior heating system works

robNL · Feb 22, 2025

Hi all,
One happy MG4 Luxury owner from the Netherlands since december 2024 so with recent updates etc, my previous car was a petrol Skoda Octavia.

I have a question about how the interior heating system works.

Coming from a petrol driven car, in the winter the car had to warm up before blowing hot air around. I guess this is partly due to a cold engine and additional heating elements needing to heat up.
In my old car I very rarely used the airco and then only either in the summer or to demist the windows. This is my first time with a car with a heat pump.

My MG4 only seems to provide warm air when the AC button is on. If I set the desired temperature to its maximum value and turn the fan on, no hot air comes out unless I also engage the airco. I just get cold air.

Is this normal (they all do that sir...) or do I need to contact the dealer about a possible fault with the heat pump?

Warm regards,
Rob

Edited to add information about age of car and firmware and my model does have a heat pump.

ReintjeWA · Feb 22, 2025

Air conditioning is more than just a way to cool the air. It conditions the air to whatever you set it to, even in ICE cars the air will heat up quicker using your aircon.

I haven’t tried this because of always have the aircon on and no real need for heating since I got the car, but I imagine you are correct in thinking the car doesn’t generate heat by itself, or at least not enough, and so needs the aircon to accomplish this.

siteguru · Feb 22, 2025

Do the models with a heat pump also still have a PTC heater? (The UK models have no heat pump but do have a PTC heater ... and after I got the latest Infotainment and HVAC updates my HVAC controls have been nigh on perfect).

MDWMG · Feb 22, 2025

siteguru said:
Do the models with a heat pump also still have a PTC heater? (The UK models have no heat pump but do have a PTC heater ... and after I got the latest Infotainment and HVAC updates my HVAC controls have been nigh on perfect).

I believe the Luxury is known as the ER in the UK, and my UK ER has a heat pump. I always have the AC on, in Eco mode, and heating is almost instantaneous.

siteguru · Feb 22, 2025

Luxury = Trophy ... the ER just means Extended Range, vs the LR = Long Range. (And SR = Standard Range).

salty · Feb 22, 2025

Rob.

Tight Git · Feb 22, 2025

MDWMG said:
I believe the Luxury is known as the ER in the UK, and my UK ER has a heat pump. I always have the AC on, in Eco mode, and heating is almost instantaneous.

Are you absolutely sure about the heat pump as no UK models have one AFAIK - where did you get the information from to say it has one?

MDWMG · Feb 22, 2025

Tight Git said:
Are you absolutely sure about the heat pump as no UK models have one AFAIK - where did you get the information from to say it has one?

Comparing what's under the black cover in the front compartment of my car with the information in the Service Repair manual (page 243) I found a Heat Pump System Valve Unit and associated pipework - photo attached.

pd2 · Feb 23, 2025

I'm pretty confident my early (72) Trophy LR has that as well, will need to check later after work.
There's no heat pump in the UK models. Might be the battery heater or similar, possibly part of the PTC system.

Lord Randall · Feb 23, 2025

EU Luxury trim (UK Trophy) has heatpump and is available in both SR and LR (49 lfp and 64 nmc packs).
EU Trophy is = UK Trophy ER, has heatpump too.

If you run an MG4 with heatpump you don't get heated air unless you set AC on.

MDWMG said:
Comparing what's under the black cover in the front compartment of my car with the information in the Service Repair manual (page 243) I found a Heat Pump System Valve Unit and associated pipework - photo attached.

Heatpump in MG4 is a black plastic box fitted in the upper part of the front compartment. On the right of the pink liquid tanks.

robNL · Feb 23, 2025

Tight Git said:
Are you absolutely sure about the heat pump as no UK models have one AFAIK - where did you get the information from to say it has one?

Mine definitely has a heat pump. Attached is the configurator page from the Dutch mg website

mg4mc · Feb 23, 2025

Back to the original question, yes models with a heat pump also have a PTC - used if the heat pump is not meeting demand.

robNL · Feb 23, 2025

I guess what I'm asking is could people please try turning the temperature control up to maximum, turn the fan speed up, note that they have hot air coming out and then turn the AC off, leave the temperature and fan speed alone and see if they just get 'unheated' air.

I'd be grateful if people could test this so I could get an idea of what I should expect. But based on Lord Randall's comment I have a feeling I know what the answer already is

. But as they saying in Dutch 'measuring is knowing'.

Kithmo · Feb 23, 2025

My 23 reg (Mk1 ?) UK Trophy gets slightly hotter when I turn the AC off, so I guess it's Uk spec and doesn't have a heat pump.

ReintjeWA · Feb 23, 2025

robNL said:
I guess what I'm asking is could people please try turning the temperature control up to maximum, turn the fan speed up, note that they have hot air coming out and then turn the AC off, leave the temperature and fan speed alone and see if they just get 'unheated' air.

I'd be grateful if people could test this so I could get an idea of what I should expect. But based on Lord Randall's comment I have a feeling I know what the answer already is . But as they saying in Dutch 'measuring is knowing'.

I just tried this and I still get hot air coming through, as if the aircon is still active. My car is Aussie spec so no heat pump.

These are the settings with hot air still coming through.

robNL · Feb 23, 2025

ReintjeWA said:
I just tried this and I still get hot air coming through, as if the aircon is still active. My car is Aussie spec so no heat pump.

View attachment 35007

These are the settings with hot air still coming through.

Thanks for taking the time to do this. I notice its 27 degrees where you are. Do you think that might also be a factor? On my car the air is cold with the airco off,not even luke warm.

ReintjeWA · Feb 23, 2025

robNL said:
Thanks for taking the time to do this. I notice its 27 degrees where you are. Do you think that might also be a factor? On my car the air is cold with the airco off,not even luke warm.

Maybe, but 27°c is a cool evening for us here, the air coming out was definitely hotter than ambient outside, as in, something was heating it up. Another factor could be that I was stationary so there was no cooling airflow or anything, perhaps that makes a difference?

NLMGSAN · Feb 23, 2025

robNL said:
I guess what I'm asking is could people please try turning the temperature control up to maximum, turn the fan speed up, note that they have hot air coming out and then turn the AC off, leave the temperature and fan speed alone and see if they just get 'unheated' air.

I'd be grateful if people could test this so I could get an idea of what I should expect. But based on Lord Randall's comment I have a feeling I know what the answer already is . But as they saying in Dutch 'measuring is knowing'.

My car (EU version Trophy ER with heatpump) MUST have the A/C on to get warm air. Even at max. Never experienced anything of a PTC heater. But with the latest software update the system runs fine.

NLMGSAN · Feb 23, 2025

robNL said:
Thanks for taking the time to do this. I notice its 27 degrees where you are. Do you think that might also be a factor? On my car the air is cold with the airco off,not even luke warm.

Reintje, the circulation is on auto. So it partially recirculates the hot air in the car.

ReintjeWA · Feb 24, 2025

NLMGSAN said:
Reintje, the circulation is on auto. So it partially recirculates the hot air in the car.

Fair point, I tried again this morning but same results, still get hot air with aircon set to off.

Understanding how the interior heating system works

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