135i Climate control

Kkuba · 04-08-2014, 09:20 PM

A few questions about the HVAC system in the 135i:

1. In full auto mode, does the system cycle the compressor on/off once the requested temperature (lower than outside temperature) is achieved? Or does it keep the compressor running, and just mix in a bit of hot air to regulate specific temperature? (obviously sunlight will have an impact here, but let's ignore it for simplicity's sake, as if this is happening at night)

If the former: if the temperature outside drops to equal inside, will the compressor cycle more off than on, then eventually, as the temperature outside drops more and more, off completely? Meaning that if you request a temperature (say, in winter) that is much higher than ambient, in full-auto mode, that the compressor will not kick-in?

The other possibility I see is that the compressor goes into an on/off cycle after it has lowered the temperature enough, say, at a 50% duty cycle, and stays like that, even if very cold outside, and simply adjusts the temperature with some hot mix, but keeps the air dry.

2. I have noticed that when I have it in full manual mode (when I set the fan, temp, A/C off, and direction to face only), and set the temp to say 25 deg and direction to face, then it only blows cool air, if I set it to 27.5, still only blows cool air. As soon as I set it to 28, it blasts hot air. What is going on here?

Occasionally, I would like to be able to operate my HVAC like a manual, non-CC one, where you turn the dial that changes how hot the air is that comes out of the vents. But it seems when it comes to heating, I can't really do that.

I suspect that this is something to do with the "fresh air on the face, warm air everywhere else" strategy that BMW employs, is there anyway of getting around this?

3. I have noticed that later 135i cars have an "ALL" button, for making one temperature knob control both temperatures. I would find this very useful, as I find myself adjusting the passengers knob to match driver's, almost every time I go to change the temperature.

Furthermore, "MAX AC" I have not yet used, although that might change when summer comes round, I think that the extra steps required to achieve MAX AC, without the button, are not that bad, and would not be done very often. An easily worthwhile trade off I think.

Is it possible to fit later model HVAC controls to earlier models?

I hope that 1 and 2 make sense...

Thanks in advance.

ItsHectic · 04-08-2014, 11:56 PM

1. It just changes the temp, slows the fan, I have never had it blow hot air when I set it to cooling in auto.

JinAM · 04-09-2014, 04:24 AM

1. BMW a/c compressors are variably changing the require pressure to cool, hence you down feel the sudden on/off clicking sound like jap cars.

2. That means there is something wrong with the system. You need to get it check out with a workshop that has factory equipment level ability. It could be a few things, ie, inside temp sensor, ihka control unit etc.

3. I am not sure whether you can change to over to the later type, but just find one and swap it in and see if it works.

jksgoh · 04-09-2014, 03:58 PM

re point 2.
I thought it was normal for the car not to blow warm air until you reached a certain threshold (relatively high). I remember it being discussed in the forums years ago, and it was considered normal… apparently so it doesn't make the driver fall asleep or some rubbish?

Kkuba · 04-09-2014, 09:27 PM

Quote:

Originally Posted by JinAM

1. BMW a/c compressors are variably changing the require pressure to cool, hence you down feel the sudden on/off clicking sound like jap cars.

2. That means there is something wrong with the system. You need to get it check out with a workshop that has factory equipment level ability. It could be a few things, ie, inside temp sensor, ihka control unit etc.

3. I am not sure whether you can change to over to the later type, but just find one and swap it in and see if it works.

1. Are you suggesting that they are variable displacement compressors? They are not common, but I guess a BMW could be classified as a 'high end' car.

2. But it only happens when on face it seems. If I have it set to manual mode but blowing on the windscreen or feet, it seems to behave like I would expect it to.

Also, in full auto mode, it seems to control the temperature accurately.

3. hmm... So your advice is to buy one so I can answer my own question, which I initially asked because I don't want waste my money buying one for it to not work.

And no, I don't know anyone with a spare later model HVAC interface just lying around in their garage/shed.

Quote:

re point 2.
I thought it was normal for the car not to blow warm air until you reached a certain threshold (relatively high). I remember it being discussed in the forums years ago, and it was considered normal… apparently so it doesn't make the driver fall asleep or some rubbish?

This is along the lines of what I was thinking might be the case

JinAM · 04-11-2014, 08:03 AM

2. There is a temp sensor on the face vent, that could be your fault. The a/c system is pretty complicate, it's hard to say what is the fault without checking it properly.
If the car is not warm up, how could you get hot air out when you set to 28? That doesn't make sense.
There is a difference in 27.5 and 28, when it's set to 28, the a/c will direct hot air out regardless to what the interior or outlet temp is currently on.

3. What I am suggesting is see if anyone in the forum is willing to swap it in for you next time you are in a meet up or something.

04-08-2014, 09:20 PM	#1
Kkuba Private First Class 25 Rep 101 Posts Drives: N54 135i Join Date: Nov 2013 Location: VIC, Australia iTrader: (0)	135i Climate control A few questions about the HVAC system in the 135i: 1. In full auto mode, does the system cycle the compressor on/off once the requested temperature (lower than outside temperature) is achieved? Or does it keep the compressor running, and just mix in a bit of hot air to regulate specific temperature? (obviously sunlight will have an impact here, but let's ignore it for simplicity's sake, as if this is happening at night) If the former: if the temperature outside drops to equal inside, will the compressor cycle more off than on, then eventually, as the temperature outside drops more and more, off completely? Meaning that if you request a temperature (say, in winter) that is much higher than ambient, in full-auto mode, that the compressor will not kick-in? The other possibility I see is that the compressor goes into an on/off cycle after it has lowered the temperature enough, say, at a 50% duty cycle, and stays like that, even if very cold outside, and simply adjusts the temperature with some hot mix, but keeps the air dry. 2. I have noticed that when I have it in full manual mode (when I set the fan, temp, A/C off, and direction to face only), and set the temp to say 25 deg and direction to face, then it only blows cool air, if I set it to 27.5, still only blows cool air. As soon as I set it to 28, it blasts hot air. What is going on here? Occasionally, I would like to be able to operate my HVAC like a manual, non-CC one, where you turn the dial that changes how hot the air is that comes out of the vents. But it seems when it comes to heating, I can't really do that. I suspect that this is something to do with the "fresh air on the face, warm air everywhere else" strategy that BMW employs, is there anyway of getting around this? 3. I have noticed that later 135i cars have an "ALL" button, for making one temperature knob control both temperatures. I would find this very useful, as I find myself adjusting the passengers knob to match driver's, almost every time I go to change the temperature. Furthermore, "MAX AC" I have not yet used, although that might change when summer comes round, I think that the extra steps required to achieve MAX AC, without the button, are not that bad, and would not be done very often. An easily worthwhile trade off I think. Is it possible to fit later model HVAC controls to earlier models? I hope that 1 and 2 make sense... Thanks in advance.
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04-08-2014, 11:56 PM	#2
ItsHectic But your honour it's my Affluenza I swear! 58 Rep 533 Posts Drives: at a reasonable speed Join Date: Aug 2011 Location: NSW iTrader: (0)	1. It just changes the temp, slows the fan, I have never had it blow hot air when I set it to cooling in auto. __________________ 135i M Sport DCT. BSM/Oyster/GP trim. FBO Cobb, Bilstein EDC coilovers, M3 bushings, PSS. Knowledge of the Tapa Tapa Tapa street race start.
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04-09-2014, 04:24 AM	#3
JinAM Private 11 Rep 87 Posts Drives: 335i Join Date: Nov 2013 Location: Melbourne iTrader: (0)	1. BMW a/c compressors are variably changing the require pressure to cool, hence you down feel the sudden on/off clicking sound like jap cars. 2. That means there is something wrong with the system. You need to get it check out with a workshop that has factory equipment level ability. It could be a few things, ie, inside temp sensor, ihka control unit etc. 3. I am not sure whether you can change to over to the later type, but just find one and swap it in and see if it works.
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04-09-2014, 03:58 PM	#4
jksgoh Major 141 Rep 1,448 Posts Drives: M2 Join Date: Oct 2008 Location: Melb, Vic, Aus iTrader: (0) Garage List 2008 E82 125i [0.00]	re point 2. I thought it was normal for the car not to blow warm air until you reached a certain threshold (relatively high). I remember it being discussed in the forums years ago, and it was considered normal… apparently so it doesn't make the driver fall asleep or some rubbish?
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04-11-2014, 08:03 AM	#6
JinAM Private 11 Rep 87 Posts Drives: 335i Join Date: Nov 2013 Location: Melbourne iTrader: (0)	2. There is a temp sensor on the face vent, that could be your fault. The a/c system is pretty complicate, it's hard to say what is the fault without checking it properly. If the car is not warm up, how could you get hot air out when you set to 28? That doesn't make sense. There is a difference in 27.5 and 28, when it's set to 28, the a/c will direct hot air out regardless to what the interior or outlet temp is currently on. 3. What I am suggesting is see if anyone in the forum is willing to swap it in for you next time you are in a meet up or something.
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