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Discussion Starter · #1 ·
As the weather has started getting colder, and I've been using the heat more I've noticed an odd behavior with my climate control.

When it is cold outside I always keep my climate control set to 70F and on the several other E39s I've owned it will initially blow hot air out of the lower/foot vents and then slowly transition to the upper/face vents where the mixing vent in the center of the upper console resides. However, my latest E39 will not do that. It seems to blow hot air out of the defrost and foot vent but only mildly chilly air out of the upper vents/mixing vent. I have it set to all the way to 3 dots and I can manually specify air to come out of the upper vent and it will actually blow hot air! Also, when it moves from lower/foot vent air only to the upper vent I can feel a small amount of heat come out of the upper/face vent and then it slowly gets colder until its at its low flow/chilled state.

my IHKA has no stored errors other than the AUC sensor, which all of my E39s have had errors for and it didn't affect this behavior. I've also gone through with INPA and manually actuated each vent and they seem to work and open fine. I'm wondering why my HVAC behaves this way and am curious if anyone has any input.
 

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Do you mean turn on the AC/cooler temp and see if the floor vents still blow hot air?
No just turn the heater temp down, if you turn on the AC that will still cool hot air so how would you know.
You likely have an issue with the valve under the hood and if hot air still blows out the floor when the heat is low that is an indicator. Just because it does not blow hot does not mean the valve is ok it just means you need to run the next test.Sorry I don't remember the other tests off the top of my head.
 

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Discussion Starter · #7 ·
No just turn the heater temp down, if you turn on the AC that will still cool hot air so how would you know.
You likely have an issue with the valve under the hood and if hot air still blows out the floor when the heat is low that is an indicator. Just because it does not blow hot does not mean the valve is ok it just means you need to run the next test.Sorry I don't remember the other tests off the top of my head.
So you're saying I have a problem with my heater valve under the hood? Are you talking about BMW P/N 64118374994? And you're saying just because I have hot air doesn't mean the valve assembly is working correctly? I don't see any leaks and I can hear the auxiliary pump running correctly with the key to position 2 and the heat on. I tried lowering the target temperature and I noticed the air got colder from all vents marginally, including the lower one.
 

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And you're saying just because I have hot air doesn't mean the valve assembly is working correctly?
That is not what I said, if it cools or works right that does not give the valve a clean bill of health. If it stayed hot that is a sure sign it is broken. Valves can stick in positions so if you can hear the pump running you should confirm the valves are moving and not leaking. You also need to confirm the electric motor is actually doing something the impeller is connected through a magnetic joint so the motor can run but the impeller seized.
 

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Discussion Starter · #9 ·
That is not what I said, if it cools or works right that does not give the valve a clean bill of health. If it stayed hot that is a sure sign it is broken. Valves can stick in positions so if you can hear the pump running you should confirm the valves are moving and not leaking. You also need to confirm the electric motor is actually doing something the impeller is connected through a magnetic joint so the motor can run but the impeller seized.
Thanks for all the patience.

I went through with DIS and manually checked that the driver and passenger side heater cores are correctly raising and lowering their temperature in accordance with the climate control and they are. I can hear the water pump running but you're right, it could be seized. I purchased a rebuild kit off ebay and I'm going to try to replace the seals as this was a junkyard one the PO put one when the original failed. I will likely be back to revisit this thread in ~1-2 months when the rebuild kit comes in and I rebuild the valve/pump. Thanks for all the help Sailor
 

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Thanks for all the patience.

I went through with DIS and manually checked that the driver and passenger side heater cores are correctly raising and lowering their temperature in accordance with the climate control and they are. I can hear the water pump running but you're right, it could be seized. I purchased a rebuild kit off ebay and I'm going to try to replace the seals as this was a junkyard one the PO put one when the original failed. I will likely be back to revisit this thread in ~1-2 months when the rebuild kit comes in and I rebuild the valve/pump. Thanks for all the help Sailor
I would inspect it rather than all that but if it is a replacement from a junkyard they don't do well when stored so likely sitting in a junkyard is worse. Those things come apart pretty easy. It could be other things, it is just that valve is the first thing to check when you have either too much or too little heat.
Anything with the 540 coolant system is nasty with the high temps and pressure. You should look around a 540 forum because there might be some common things that happen to that car that don't happen to the other models.
 

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It seems to blow hot air out of the defrost and foot vent but only mildly chilly air out of the upper vents/mixing vent.
Wait, this sounds pretty normal to me, across both my old E36, 540i, and current M5. When the heat is on, the hot air only blows out the lower vents. The upper vents are either no airflow on your face (red dots) or increasing amounts of cooler airflow (blue dots). Thought the manual said something about fresh cool air in the winter to help keep you awake and alert or something. Am I to understand it that all of my cars have be broken in the same manner, and turning the dial to the red dots should give hot airflow from the upper vents?
 

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Discussion Starter · #13 ·
Wait, this sounds pretty normal to me, across both my old E36, 540i, and current M5. When the heat is on, the hot air only blows out the lower vents. The upper vents are either no airflow on your face (red dots) or increasing amounts of cooler airflow (blue dots). Thought the manual said something about fresh cool air in the winter to help keep you awake and alert or something. Am I to understand it that all of my cars have be broken in the same manner, and turning the dial to the red dots should give hot airflow from the upper vents?
Mine all work that way. It is not as hot as what comes out the floor because the air path is different.
So I'm basing this off my previous E39's that I've owned. But usually at about 45C coolant temp I would get hot air blowing on my feet and then at around 65C coolant temp after the cabin had heated up a bit it would transition to blowing hot air from the upper vents as long as I had the 3 red dots selected. Of course this was on a 530i however I can imagine the HVAC behavior between the cars would be similar? It seems odd for the behavior to change with I6 vs V8
 
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