On Thu, 21 Sep 2017 17:44:04 +0000 (UTC), Chaya Eve
wrote:

On Wed, 20 Sep 2017 18:39:50 -0700 (PDT), trader_4
wrote:

One thing I recently learned is that when you have the AC compressor
switch set to on, it appears that it basically runs it with the AC
full on and uses the heater to then warm the air to the set temp.

Interesting. I didn't know that, but on the E39, the BMW mindset seems to
be similar in that it's really a PITA to set things up because they don't
want you to touch it, where you're "supposed" to fine-tune adjust
temperature only by adjusting the "mixture" of hot and cold air.

So it's the same BMW mind set on the E39 as you mentioned for your X5.

In the E39, you set the "desired" passenger/driver temperatures with a
multi-button-push method that you don't want to do every day. And then
you're supposed to leave that passenger/driver temperature setting forever
and not touch it again.

What that means is that you can't set the interior temperature at the time
you start the vehicle. The computer figures it out based on whatever it
bases it upon (probably the delta between ambient and your permanent
setting).

Then, almost the way you mentioned above where you "heat the AC" air,
you're "supposed" to control the fine-tuning of the temperature merely by
letting the computer do all the work where all you do is twist the one
cold/hot blue/red knob that adjusts the portion of hot air and cold air
coming out.

So you don't have the kind of easy twist-knob controls like most cars have.
It's fine if you really don't want to adjust the temperature, but if you
want to adjust the temperature, it's a dozen button presses. Sigh.

I can understand the need to do that to some extent, to remove
humidity. You want to drop the air temp to remove humidity, then
warm it back up.

I never heard that, but maybe that's the reason.

But when it's not humid, it's a waste of energy to run
the AC compressor excessively. You would think when they are desperate
to increase mileage to meet govt reqts that reducing the AC load
would be something that could be easily done.

Yes. But. You probably test smog/mileage with the AC off.

A humidity sensor
for example. Also they target an AC coil temp just a couple deg
above freezing, while other cars appear to maintain a higher temp.
So they are constantly chilling air down to near freezing, only
to heat it back up to get it to 72F.

I didn't know about that.

BMW engineers are a strange lot.
Virtually all cars with "automatic temp control" or "climate
control" work the same way - just the the Chermans need to put their
own (twisted) twist on everything. Teutonic engineering.