[s-cars] AC high pressure switch

[Joshua Van Tol]

It could also be the speed sensor failing on the compressor. How long did
it take for the AC to cut off? If less than a few seconds, there's just no
way that it could be high side pressure. The fact that it doesn't turn back
on points to something other than the pressure switch. You might be able to
re-code the control head for a denso compressor, which lacks the speed
sensor to check this theory.

The head unit does have diagnostics, and will tell you if the speed sensor
is bad or it's cutting off due to high head pressure.

My diagnosis is that it's time to get a VAG-COM and a gauge set and ditch
the shop.


On Thu, Jul 24, 2014 at 3:01 PM, Erik Addy <erikaddy at yahoo.com> wrote:

> Sorry I didn't reply to this earlier, I had to go out of the country for
> work and my personal emails sort of fell off my radar.  Anyway, I believe
> they put a gauge set on it.  Syptoms prior to brining it in were that
> frequently when I would start the car in the morning, the A/C compressor
> would engage (no noted abnormalities like dropping idle RPM or noise), and
> then immediately shut off and the snowflake symbol would disappear.
>  Occasionally, it would stay on and operate normally for the whole drive
> (typically 10-20 min).  After they worked on it, it worked every time for
> about a week or so, but now it is back to the symptom above.  Makes me
> wonder if they unplugged/plugged back in some connections and that make the
> contact better, which is why it worked for a while.
>
> Since it happens frequently right after a stone cold start, I can't
> imaging it is a blocked condenser or fan (but I've been wrong many times
> before).   I could see a partial block at the orifice tube or something...
> Where is the cut out switch?  Must be different than the switch that
> normally turns off the compressor, right?  Otherwise, why would the
> snowflake go away and the compressor not try to turn back on after the
> pressure drops?
>
> Erik
>
>   ------------------------------
>  *From:* Joshua Van Tol <josh at spiny.com>
> *To:* Erik Addy <erikaddy at yahoo.com>
> *Cc:* S-car-list <s-car-list at audifans.com>
> *Sent:* Tuesday, July 15, 2014 7:27 AM
> *Subject:* Re: [s-cars] AC high pressure switch
>
> What makes them think the problem isn't real? The switch is likely
> normally closed, so that it can be wired in series with other protection
> devices.
>
> If the symptom is the AC works fine when the car is at speed, but
> sometimes quits right after start up or when in traffic, then I think you
> need to look at reasons why you might not be getting enough condenser
> airflow.
>
> Is the aux cooling fan working? If it is, is the viscous clutch on the
> engine driven fan worn out? Last but not least, the condenser might be
> plugged up with bugs.
>
> My S6 had a worn out barely working aux cooling fan, and the viscous
> clutch was worn. Replacing both fixed the AC. Cooling of the engine was not
> affected.
>
>
>
>
>
>
> On Mon, Jul 14, 2014 at 3:39 PM, Erik Addy <erikaddy at yahoo.com> wrote:
>
> So my AC is sometimes not working, throwing a code for the high pressure
> switch.  Shop says pressures are good, think it's an electrical issue.  Can
> any one tell me the location of the switch, and if open or closed circuit =
> high pressure cut off?
>
> Thanks!
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