On 12/30/2015 3:19 PM, Jeff Wisnia wrote:
I'm posting this here because all the Jeep sites I can find on usenet look like
they've had next to no new posts on them for the last year or more.

And, there seem to be more knowledgeable folks here than on many other newsgroups.

This isn't a "problem", but my inquiring mind is just looking for an answer:

SWMBO drives a 2014 Jeep Compass. On the occasions when she's driving the two
of us somewhere in her car and stops to run into a store for something, leaving
me in the car with the engine off and ignition key out, I notice this happening.

About three minutes after the car is shut down I hear a whirring noise which
sounds like small electric motor. That noise appears to come from under the
dashboard and lasts about two seconds. When that noise stops a second similar
whirring noise starts and lasts for about the same time as the first one, but
it has a slightly different pitch and seems to come from a different place in
front of me.

My best guess is that the noises are coming from small electric motors which
are doing something like moving flap valves in the car's HVAC ducts, but I
don't understand why they don't do that as soon as the car is shut down.

Probably.

As to timing, the controllers running the car have their own idea of
what needs to be done, when. Radiator fans are electric, nowadays
(most vehicles, even those without transverse engines) and run on
to bring the temperature of the coolant down -- even though the
coolant isn't being actively *pumped* through the stopped engine!
Perhaps similar reasoning applies?

Why not look at the locations of the various flaps and monitor
them in one such experiment? Or, pull the cabling to one and see
if it stops making that noise? Note that it may be a single
actuator doing "double duty" -- moving two different mechanisms
at two different times (one to take outside air into the
cabin, another to route "treated" air to the top and/or bottom
ports, etc.)

http://www.autozone.com/1/products/118109-a-c-heater-blend-door-actuator-604-035-dorman-604-035.html

http://www.justanswer.com/jeep/7cdwb-compass-2008-jeep-compass-heater-ac-blower.html

Workshop manuals make these sort of questions a lot easier to resolve
(with a lot less "actual work"! : )

If someone here knows for certain what is making those noises I'd sure like to
know.