640d Heater Issue?

Discussion in '6 Series' started by imi7, Apr 19, 2019.

  1. imi7
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    imi7

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    Just thought I would ask the following as I cannot remember coming across this before:-

    I have a 2015 640d - Mileage at 24k. This week I have experienced that when I adjust the Climate control between 16-27.5C, the air being blown out is the same throughout (A/C is OFF, Centre Hot/Cold wheel between front vents set in the middle). As soon as it sets to 28C then hot air blasts out. Anyone else come across this?

    Also - not sure of this affects the above, but 2 months earlier the Dealer had taken out the dash completely to fix a previous issue.

    I have extended warranty on the car with the same dealer, and booked it in for a check on the above issue- any advice would be welcome.
     
  2. Peter
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    Peter WARLORD Site Supporter

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    I note you say the A/C is off. What's the difference when A/C is on? Why I say this, what is the ambient temperature? If ambient is quite high and you are needing to cool the car, and there is no cold air, it may simply be blowing as cold as possible without A/C support.

    You reference the temperature range and then specifically 28C. 28C is unregulated heating, compared with the regulated range to 27.5C. If it is trying to cool (cabin's quite hot) then you switch to 28C, it will go into full heat mode, that is by design.

    I'd try with A/C on, see if it is functioning correctly. Plus try different air flow intensity levels.

    Peter
     
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  3. Mieke
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    Mieke WARLORD Site Supporter

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    Why would you need to turn the AC off anyway? It should be run all year round to prevent contaminants building up in the system.
     
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  4. Peter
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    Peter WARLORD Site Supporter

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    Agree, plus Climate Control is limited without the A/C function.

    It doesn't take a very high ambient temperature to stop efficient cooling, without A/C. There is so much heat soak in the system components and bulkhead area that I find anything above say 14C, and you notice that it can't cool properly if the sun is shining in the car. A/C sorts that in a heartbeat.

    Peter
     
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  5. imi7
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    imi7

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    Thanks for the info. The ambient temperature was around 18C.

    I did not realise that it is best to leave AC on all year round...will bear this in mind going forward.

    It has also been suggested that maybe the Dealer failed to reconnect a Stat during the last dash repair - and as Peter stated that at 28C the Stat is ignored and blasts out heat anyway.

    I tried the AC and it is working OK at all intensity levels.

    My thoughts are, when the AC if Off and the ambient temp not being too high, that at least at 16-18C it should be blowing out reasonably colder air than at 25C?
     
  6. Peter
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    Peter WARLORD Site Supporter

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    Good to read your Climate Control is working better with A/C turned on.

    On the heat settings, remember it is not just outside ambient temperature, add actual cabin temperature and inputs from the solar sensor to the HVAC commands. Gets complex, and if we don't run a full auto mode (including A/C) we can appear to be running HVAC conflicts. Like the temperature of the air not appearing to steadily rise with dialling in more temperature. Sunshine can mean there is no call for heat, could even be near a perfect blend, or even the opposite, it could still be requesting colder air as you turn up the heat. A cloudy day and the function can be totally different.

    Even using a thermometer at the vents, may not fully explain the actual function. I assure you when the A/C is off and ambient temperatures start climbing above 15C, there is a lot of heat about on a sunny day. Easy to assume the HVAC system is messing you about, even set at something like 20C, turn the A/C on and leave on auto and the cabin stabilises very quickly.

    Peter
     
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  7. imi7
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    imi7

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    Thanks Peter - I have left AC on now - I guess I thought turning it off over the winter months was the correct thing to do as AC was not needed.
     
  8. Peter
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    Peter WARLORD Site Supporter

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    Climate Control (it's in the name) works much better and is less intrusive when the A/C function is switched on. CC is not the same as systems where A/C is almost a stand alone feature of a more basic HVAC system.

    In my own driving in the Highlands, typically colder than further south, still find the A/C function is more important in the cooler months, than simply when there is high demand for cooling. Keeping the car dry, with the dehumidifying function, preventing misting when getting in with wet clothes, or generally high humidity and large temperature swings. Runs without need for manual intervention, works efficiently with low air flows.

    Using A/C all year, doesn't make much difference to economy in our larger engine cars. Remember the energy demand from A/C is low in cooler months anyway, and variable output compressors mean they are pretty efficient anyway. It is hot days in summer when the energy demand is high, That's when it costs most to run A/C.

    Peter
     
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  9. K777
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    K777 WARLORD Site Supporter

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    I always had a/c on in my 640d in cold months, if not it misted up all to easy.
     
  10. imi7
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    imi7

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    Quick update - I have delayed my Dealer appointment, but decided to test out different scenarios based on the advice/comments above.
    On a cloudy day, outside temp 14C, with the centre dash wheel on Red, AC ON, as I increased the temp from 20-27.5 there was no heated air coming out of the vents, but once again at 28C hot air blasts through.

    Could there be a faulty sensor somewhere?

    AC function works fine. Just seems the call for heat is being ignored.
     

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