[s-cars] 95.5 S6 No/Low Heat

[Joshua Van Tol]

Actually both the type 44 and the S6 have a similar system. They use a flap
for regulation, and *also* have a valve. The valve functions to totally
stop the flow of water through the heater core, and is used when cooling to
reduce heat pickup from the hot heater core. The valve is either on (when
introducing any amount of heat) or off (when cooling) and isn't modulated.

I used to work designing automotive HVAC controls, and water side
modulation is very very tricky to make work well. The lag time is enormous,
and coolant flow is tricky to control unless you measure it.

On the S6 the flap is driven directly by an actuator, on the 44, it's
driven by a bowden cable, which is driven from a box that has a servo, plus
a couple of vacuum valves, which drive some of the other flaps.


On Fri, Feb 5, 2016 at 9:45 AM Peter Golledge <petergolledge at gmail.com>
wrote:

> Heater should be hot all of the time since the flap regulates temp not a
> valve like earlier type44.  I would back flush with a garden hose adapted
> with some hardware store fittings, don't use massive pressure though... can
> rupture the core!
>
> Having said that, motor brushes wear down, I'd replace the servo while you
> are in there.
>
> On Fri, Feb 5, 2016 at 8:18 AM, Paul Luevano <paul at clarity.net> wrote:
>
> > On 2016-01-08 09:07, Paul Luevano wrote:
> >
> >>
> >> List-
> >>>
> >>> It's getting cold in the northeast, so of course the heat in my S6 is
> >>> getting flaky.
> >>>
> >>> Noticed the other morning that the car was never heating up.  It
> usually
> >>> gets to temperature, even on the coldest mornings, in 5-10 minutes.
> Now,
> >>> at the end of my (admittedly short commute), the car is barely
> starting to
> >>> warm up.
> >>>
> >>> Did a little digging this morning, and while the dash gauge is showing
> >>> normal temp (thermostat just replaced in preparation for the winter),
> no
> >>> matter where I set the climate control settings (dash, floor, center
> vents,
> >>> etc.), it is blowing cool to luke warm air at best.
> >>>
> >>
> >         Just revisiting this issue.  I had assumed it was likely a faulty
> > temp flap servo, but when I dug into it, the servo was moving freely as I
> > cycled from "Lo" to "Hi".
> >
> >         I *did* notice that while the lower heater hose feeding the
> heater
> > core, the upper return hose was, at best, luke warm.  Good photo here:
> >
> >
> >
> http://i187.photobucket.com/albums/x242/austinado16/Audi%20A6%20temp%20control%20motor/P1020989_zps1623b883.jpg
> >
> >         I did bring up the CC codes, and all I got was a "15.7 Air Flow
> > Flap, sporadic block".
> >
> >         Now what is odd, is every now and then, I will get full heat.
> > Seems like once the car is up to temp, if I shut it down, and restart, I
> > then have heat.
> >
> >         Any idea what I should look at next, what channels on the CC head
> > I should be looking at for insights?
> >
> >         Thanks!
> >
> > Paul Luevano
> > Wakefield MA
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