Question about automatic climate control...

[paris1]

So as a new owner of a 2013 35i, I'm finding one of the most baffling systems on the car to be the automatic HVAC. Damn thing seems to have a mind of its own, but then maybe that's by design! Adding to this obtuseness is that the section in the owners' manual dealing with this has got to be the worst section of this generally useless publication!

So let's start with a simple question. How in the hell do I get this thing to simply pass ventilation air through the cabin without heating it? Is this simple function a lost art among Bavarian engineers? I have tried everything I can think of and the system always seems to add heat to air coming into the cabin, even on the lowest temp setting. This, as you can imagine, is not helpful when it's 75 degrees outside here in Calif.!

[Eltee]

Have you tried moving the dial (located inbetween the two center vents) towards the blue side (cold)? If it is turned towards the red/ hot side you're going to get heat even if the temperature dials are set colder than ambient temp.

Seems as if this simple mechanical dial overrides whatever temperature is set even if it is just the air out of the upper vents.

[rking117]

I think you can turn off the AC via the button and then turn the nobs down to be lower than the outside/inside temperature and it will just vent.

[paris1]

Originally Posted by rking117

I think you can turn off the AC via the button and then turn the nobs down to be lower than the outside/inside temperature and it will just vent.

Nope. When I do that the resulting airflow is warm!

[Putzo]

Originally Posted by paris1

So as a new owner of a 2013 35i, I'm finding one of the most baffling systems on the car to be the automatic HVAC. Damn thing seems to have a mind of its own, but then maybe that's by design! Adding to this obtuseness is that the section in the owners' manual dealing with this has got to be the worst section of this generally useless publication!

So let's start with a simple question. How in the hell do I get this thing to simply pass ventilation air through the cabin without heating it? Is this simple function a lost art among Bavarian engineers? I have tried everything I can think of and the system always seems to add heat to air coming into the cabin, even on the lowest temp setting. This, as you can imagine, is not helpful when it's 75 degrees outside here in Calif.!

I have noticed this issue with both of my BMWs and have given up trying to understand it. I now live with it and end up using the A/C more than I would on any other car make.

[nicknaz]

Try turning off the "auto" mode, turning the dial by the vents to blue, and setting the temperature to 60f (coldest it will go).

[paris1]

If I'm not mistaken (and I haven't got the car here now) the system automatically defaults to auto mode upon startup. Is there a setting to defeat this?

[C.D.335xi]

I previously had a E92 335 with an N54 engine that exhibited the same behaviour and I have the same issue with my Z4 (which also has an N54). Based on numerous posts on the 3 series forum, it appears to be largely attributable to the N54 - the engine gives of a significant amount of heat that is not effectively dissipated, affecting the temperature of the air flowing through the vents when the AC is off. In the 335 this also manifests itself in reports of the sides of the transmission tunnel in the footwells also being hot to the touch. If you search the 3 series forum you will find a number of posts from E90 and E92 owners with the N54 engine citing these issues.

In my experience, although it is an issue in the Z4, with its less densely packed engine bay (which seems to allow for better heat dissipation), it is comparatively less of an issue than it was in my E92.

[paris1]

Originally Posted by C.D.335xi

I previously had a E92 335 with an N54 engine that exhibited the same behaviour and I have the same issue with my Z4 (which also has an N54). Based on numerous posts on the 3 series forum, it appears to be largely attributable to the N54 - the engine gives of a significant amount of heat that is not effectively dissipated, affecting the temperature of the air flowing through the vents when the AC is off. In the 335 this also manifests itself in reports of the sides of the transmission tunnel in the footwells also being hot to the touch. If you search the 3 series forum you will find a number of posts from E90 and E92 owners with the N54 engine citing these issues.

In my experience, although it is an issue in the Z4, with its less densely packed engine bay (which seems to allow for better heat dissipation), it is comparatively less of an issue than it was in my E92.

Ironically, NC Miatas (the world I came from prior to purchasing this Z4) have the same issue with heat build up under the hood and induction into the HVAC system at low speeds. I've noticed the N54 puts out quite a bit of heat particularly on the right side of the car (where I assume the turbo lives, though I haven't had a chance to really study under the hood much) where the right front fender and hood get quite warm after a run.

[Asbjorn]

Originally Posted by C.D.335xi

I previously had a E92 335 with an N54 engine that exhibited the same behaviour and I have the same issue with my Z4 (which also has an N54). Based on numerous posts on the 3 series forum, it appears to be largely attributable to the N54 - the engine gives of a significant amount of heat that is not effectively dissipated, affecting the temperature of the air flowing through the vents when the AC is off. In the 335 this also manifests itself in reports of the sides of the transmission tunnel in the footwells also being hot to the touch. If you search the 3 series forum you will find a number of posts from E90 and E92 owners with the N54 engine citing these issues.

In my experience, although it is an issue in the Z4, with its less densely packed engine bay (which seems to allow for better heat dissipation), it is comparatively less of an issue than it was in my E92.

I totally agree. With N54 Z4s the air is unintentionally heated by the engine, not the climate control. So Z4 owners have two options

1) Turn on the A/C.
2) Put the roof down.

You fail if you select option number one.

[nicknaz]

Originally Posted by paris1

If I'm not mistaken (and I haven't got the car here now) the system automatically defaults to auto mode upon startup. Is there a setting to defeat this?

It might be a change across model years, but HVAC doesn't default to auto on my 2012. If I put a manual setting then turn off and lock the car, when I get back to the car it will retain that setting.

By the way, I tried my suggestion above and it puts ambient temp air into the cabin. I wasn't hammeriing on the car so I can't verify whether or not the air would have been heated by the engine (oil gauge was at 210F when I gave up being eco and turned the AC back on)

[ManiacGT]

I think HVAC is set against your key. Mine is on my 09 car. It remembers however the car was setup per key.