Cabin heater hunting the target temperature

[RP67]

I'm not complaining about the offset of the temperature reading, it is inconvenient, but that's it, or the range drop with the AC on, that's pretty much already covered in other threads. However during a recent trip (the first long one with the MG4), I have noticed the heater is not quite as smooth as it is expected nowadays. I managed to set the temperature to 26 degrees, which is about 3 degrees higher than I usually do in my recent cars. Fan speed on 2, just to keep the mist off from the windscreen and to get some airflow to the cabin. It was fine for awhile, we felt the temperature rising reasonably quick, and become comfortable. Suddenly it decided it was too much, so started to cool the cabin. I mean the air blown in the cabin, was pretty much freezing cold. Then the cabin temperature dropped, and the heater started to heat again. The temperature differential could be around 15-20 degrees (the blown air), which was very unpleasant.
Not sure whether it is the "normal MG4" way to control cabin temperature, or should I get it checked by the dealer?

 

[Rolfe]

I've seen one or two people on the forum complaining of the same problem, although I don't know if anyone has had it develop some way into their ownership of the car. I think it's a fault and you should talk to your dealer about it. I'm not noticing this with my car.

 

[CooperS]

I have posted previously about the heating/ac system in my current car an EV6. Despite software updates it still doesnt heat properly and will cool as you describe. I thinks its an EV issue as there is no ‘hot’ water as in an ICE car and we are depending on electronic systems to heat.

 

[Rolfe]

Why does it only affect some cars, then?

 

[CooperS]

I dont know, I have not had problems that others have had. Says he touching wood! It is very random how issues affect some and not others? Theres probably a law for it

 

[Rolfe]

I think it's something sticking. Physically, I mean.

 

[Spaniard]

Don't overthink about it.. the mg4 has a poor climatiser.
Other brands use several temperature sensors (e.g. VW bi-zone) including sun sensors to compensate its effect on the skin increasing the cold. Nothing like that is in the mg4, so do not expect miracles

 

[RP67]

I've seen one or two people on the forum complaining of the same problem, although I don't know if anyone has had it develop some way into their ownership of the car. I think it's a fault and you should talk to your dealer about it. I'm not noticing this with my car.

Thanks for the comments, I expected to be smoother and to be fair, there is "water" and it is heated/cooled by a "machine" (either you call it heat pump or not), and it is supposed to be controlled a lot more precisely.

 

[RP67]

Don't overthink about it.. the mg4 has a poor climatiser.
Other brands use several temperature sensors (e.g. VW bi-zone) including sun sensors to compensate its effect on the skin increasing the cold. Nothing like that is in the mg4, so do not expect miracles

You've got the point, but avoiding heating to cooling within two minutes, and back to heating again after a couple of minutes shouldn't be a miracle...

 

[Rolfe]

Mine doesn't have a heat pump, but received wisdom seems to be that the heat pump does a better job. I don't have a problem with mine. I was driving home at 5 degrees the other night and periodically turning the heating down a degree at a time as I was feeling quite warm, and I didn't experience any sudden shifts.

 

[AdeSc]

Mine doesn't have a heat pump, but received wisdom seems to be that the heat pump does a better job. I don't have a problem with mine. I was driving home at 5 degrees the other night and periodically turning the heating down a degree at a time as I was feeling quite warm, and I didn't experience any sudden shifts.

I’m really curious as to how your car heats and cools if it doesn’t have a heat pump. What system does it use please?

 

[Ian Key]

Have a look at the heating screen and see if ECO is switched on. If it is that could be causing the fluctuations in the temperature.

 

[tsedge]

I’m really curious as to how your car heats and cools if it doesn’t have a heat pump. What system does it use please?

The UK spec has normal AC for cooling and a PTC Heater for heating. This is standard for cars without a heat pump. And indeed it was the only option before heat pumps were introduced to EVs.

 

[AdeSc]

The UK spec has normal AC for cooling and a PTC Heater for heating. This is standard for cars without a heat pump.l and indeed was the only option before heat pumps were introduced to EVs.

Huh. Live and learn. I did not know that, I assumed all AC. Thanks for the info.

 

[JonnyG]

............It was fine for awhile, we felt the temperature rising reasonably quick, and become comfortable. Suddenly it decided it was too much, so started to cool the cabin. I mean the air blown in the cabin, was pretty much freezing cold. Then the cabin temperature dropped, and the heater started to heat again. The temperature differential could be around 15-20 degrees (the blown air), which was very unpleasant.
Not sure whether it is the "normal MG4" way to control cabin temperature, or should I get it checked by the dealer?

I have noticed similar with mine on occasions. It seems to be blow warm or cold but unable to maintain a constant temperature very well on long journeys. I've put mine on ECO with a lowish manual fan speed and that seems to minimise the effect.

 

[Coulomb]

And indeed it was the only option before heat pumps were introduced to EVs.

Some cars actually use a "kettle", i.e. a resistive element under the bonnet connected to the cabin by heater pipes. As opposed to the PTC which is inside the cabin.

I think the kettle might be more common on models that are also available with an ICE powertrain, as the same plumbing can be used for both.

 

[tsedge]

Huh. Live and learn. I did not know that, I assumed all AC. Thanks for the info.

AC doesn't heat, it is about cooling in a similar way to a fridge (cold inside, waste heat goes outside) and AC will also reduce humidity.

Conventional ICE cars use waste engine heat to provide heating and if the AC is on then the humidity of the air is also reduced, hence the use of AC in winter to quickly clear the windows and windscreen. With ICE there's tons of waste heat, but only when the engine is warm, which is why warming up the car on winter mornings is such a pain.

On EVs, using a PTC heater gives instant heat (think electric fire) which is great for winter warm-ups, although it will sap the battery.

Heat pumps are like enabling bidirectional AC: they can heat and cool and do so very efficiently, so they use much less energy - however they struggle to provide a huge blast of heat, which a PTC heater can do, so they can be less effective for a quick temperature change - it all depends on the quality of the design and engineering.

I am happy to be corrected on any of this but this is my understanding.

 

[GameZone]

This is normal behaviour on my car. I think it does this in order to save electricity once reaching a certain temperature. It doesn't bother me that much though. When it's cold outside I normally just leave it at 24, and I usually have to drive long distances before it switches to cold air. If unpleasant I just turn the temperature up again. And my car does have the heat pump.