[s-cars] Climate Control - Damn the Snowflake

[Tom Green]

I don't think you have much to worry about on the speed sensor issue-- 
unless it is a faulty sensor.  Any mismatched signal will indeed  
leave a fault
code when it shuts down the compressor.  More noteworthy is the fact  
that just a minor drag on the serpentine belt will cause it to shred  
into 1628
separate 1mm pieces in short order, with catastrophic results very  
likely.  Just inspect the belt regularly and be aware of new noises  
underhood.

One of the first system condition checks is to put a thermometer  
probe in the center vent with system running on LO at 2K rpm, with  
about 40F
desired at the normal 95F DC summer temps.  Check the aux fan  
operation and condenser airflow during this time.  You can easily  
gage the
high pressure with a gage set.  Bentley would have you believe  
checking the low pressure side is easily done, but I have not found a  
connector
that will allow connecting a gage to the low pressure side.  Just the  
high pressure check should show 290 psi--lower means poor system
performance due to insufficient refrigerant charge--much higher will  
trip the sensor or even vent through the relief valve.  The low  
pressure side
measurement would allow checking the system balance and proper  
operation without opening up the system.  I think you recognize that  
opening
the system is the last resort even if you have all the equipment to  
capture the refrigerant, evacuate and refill with the proper measure  
of oil and
refrigerant.  I didn't even mention a state certification and license  
to do so.  :-)  The system pressure will be about 100psi with the  
compressor
off if you were thinking of just hooking up a 12 oz can to the high  
pressure port--not recommended--and difficult to get the refrigerant  
to flow in
the desired direction.

This system is marginal and lacks the excess capacity built into many  
US cars, so it takes time to cool down a vehicle parked in the hot  
sun and
doesn't like stop and go traffic in DC summers.  So, keep the  
condenser clean, the aux fan working properly, check the high  
pressure side  for
proper charge, and keep the filter changed if you use one.  Parking  
in a shady spot helps that black beast the most.  After that, the  
difficulty and
price escalate.

Tom

-----Original Message-----
> Date: Fri, 22 Jun 2007 09:13:15 -0400 (EDT)
> From: <manuelsanchez at starpower.net>
> Subject: Re: [s-cars] Climate Control - Damn the Snowflake
> To: djdawson2 at aol.com, munrof at sympatico.ca, rit_bellis at hotmail.com,
> 	s-car-list at audifans.com, s.sikss at gmail.com
> Message-ID: <20070622091315.DAT35805 at ms03.lnh.mail.rcn.net>
> Content-Type: text/plain; charset=us-ascii
>
> Fellow S-heads,
>
> I checked all the codes in the CC Head per the 12v.org site (Thanks  
> Vincent)
>
> Currently there were no stored codes in any of the channels that  
> would list faults, such as Channel 1, System Malfunction. Channel 1  
> read 00.0.
>
> I found some old paper work in my records where I had done this a  
> year or so ago, and the code stored in Channel 1 back then was:
>
> 8.7-Temperature Regulator Flap-Sporadic Block
>
> Would the 8.7 code cause the snowflake to come on and off (I  
> somehow think that would be an unrelated symptom, like when I  
> occasionally would get hot air coming thru the vents even with the  
> climate control blower off)?
>
> I checked the channel for the compressor speed (Channel 29)  
> relative to engine speed (Channel 28) and with the multiplier  
> (Compressor=1.28 x engine speed) all seems fine. I am correct in  
> assuming that if there were ever a discrepancy between the 2 speeds  
> a code would show up somewhere in the system diagnostics or are  
> these 2 channels like the channel that display the speed of the  
> car, an actual value at that specific moment in time that is not  
> stored? In other words, when the snowflake goes off the next time,  
> I'll need to toggle to those channels to see if at that exact  
> moment the speed differential exceeds the stated 1.28 multiplier  
> value?
>
> Thanks again for any insights.
>
> -Manny
> 95.5 UrS6 Avant (Flaky Snowflake)