how much does the AC run?

[rsfeller]

I noted that if I take the AAC off of AUTO and put the temp on 85 it will begin to get warm if the A/C is disengaged. Even knowing it is 60F outside this evening and I have the AAC on 85 the AC trys to engage.

Now I know AAC systems will use the AC compressor for de-misting and they can run often...but should not the AC compressor be disengaging when ambient temp is far below the setting on the AAC?

I will get the car into a shop with the PST2 soon...but I'm curious if the AC is basically always running on the 986 or is it a symptom of my failure in the system.

[Loren]

System description

Heating section

The heating system is controlled on the air side, i.e. coolant continuously flows through the heat exchanger. The heating is regulated via the position of the temperature mixing valve.

Depending on the position of the temperature mixing valve, a certain portion of warmed airis mixed with the fresh air from the outside.

Air-conditioning section

The preselected temperature is controlled automatically. The interior temperature and air flow can be adjusted manually via two pushbuttons. The changes are shown in the display. Information from the outside temperature sensors, interior temperature sensor and the sun sensor is processed to regulate the interior temperature. The system can respond to rapid changes in the outside temperature and also takes into account that the intensity of sunlight has a major influence on the subjective temperature perception of passengers.

The fully automatic control system influences the temperature distribution between the upper and lower areas of the passenger compartment to suit the desires of the passengers in most cases. It is nevertheless possible to control this distribution manually by means of the corresponding push buttons. As in other Porsche cars, the air-conditioning system of the Boxster (986) is equipped with a "Defrost" button, which ensures maximum window defrosting efficiency by suitable control of the heating and blowing power and air distribution. In the interest of simpler use, only one button has to be operated here to direct the full heating power to the windows in order to ensure rapid defrosting when the vehicle is operated in wintry conditions.

A quantity-controlled compressor produces the cooling power of the air conditioning.

With this demand-dependent quantity control, the compressor makes a contribution towards energy savings. When the compressor is switched on, only approx. 6 % of the refrigerant quantity is pumped. The start-up jerk that occurs with uncontrolled compressors can largely be avoided in this way.

[rsfeller]

Loren,

thanks for taking the time to research and copy/paste. Very informative information...but I'm not seeing my answer about the AC compressor running ALL the time. I love to drive myself nuts with theories when I know the PST2 is my only sure answer.

Does this information come from a factory Tech CD (Bentley DVD?) or another source, I'm curious.

Shawn

[Loren]

If it is on "Auto" it will run most of the time. Still the problem could be a sensor....

Control of the air-conditioning compressor

Activation of the air-conditioning compressor depends on the outside temperature, intake air temperature and coolant temperature.

Activation: - Outside temperature >= 5 °C

- Intake air temperature > 3 °C

- Coolant temperature < 115 °C

- Ignition on

The air-conditioning compressor is switched on 7 seconds after the engine is started, at the earliest.

[rsfeller]

If it is on "Auto" it will run most of the time. Still the problem could be a sensor....

Control of the air-conditioning compressor

Activation of the air-conditioning compressor depends on the outside temperature, intake air temperature and coolant temperature.

Activation: - Outside temperature >= 5 °C

- Intake air temperature > 3 °C

- Coolant temperature < 115 °C

- Ignition on

The air-conditioning compressor is switched on 7 seconds after the engine is started, at the earliest.

Based on those specs it appears that the AC is operating as expecting...the sensors or control valve is obviously not allowing enough flow from the "hot side" then. I would assume there is a flap that shifts the mix from the AC flow side to the heater core side like most automobiles.

As much foam as my car has shooting out the air vents I'm still thinking that foam may have either clogged up the heater core some or posibly wedged itself inot the mix flap (seen that happen on my Vw Eurovan once)...but the sensor idea is most likly dead on too. I removed the cockpit temp sensor on the pass. side this evening and blew and cleaned off the sensor. It was amazingly caked with dust. Again I've seen this on my Saabs and a cleaning has been know to solve problems...but not today!

I have an email into my regional PCA.org for recommendation on shops or owners of PST2. I'm sure they will want me to join before sharing good info!

Do you happen to know what perks other then events/meetings/racing belong to PCA.org is? Are their tech documents good or the basic info I can already get on great BB like this? Funny they want you to join but do a poor job of explaining the perks of joining (IMHO).

[Loren]

IMHO - PCA is the yearly membership fee just for the monthly magazine (Panorama). We work with our local regions (their are 4 just in the general bay area here). We help with some tech sessions, parade laps, fun drives, etc. and we do our local "Work on cars days".

[rsfeller]

If it is on "Auto" it will run most of the time. Still the problem could be a sensor....

Control of the air-conditioning compressor

Activation of the air-conditioning compressor depends on the outside temperature, intake air temperature and coolant temperature.

Activation: - Outside temperature >= 5 °C

- Intake air temperature > 3 °C

- Coolant temperature < 115 °C

- Ignition on

The air-conditioning compressor is switched on 7 seconds after the engine is started, at the earliest.

We'll I just got several emails back from the Durametric "peeps" and I figured this information would be of use to you as the guru.

They claim that the section in the Durametric Software called Air Condition tests all sensors in the AAC system. They claim if there was a voltage or ohm reading out of spec within the servos, flaps and fans of the AAC their software would pick it up the same as the PST2. I only inquired as they called their section Air Conditioning and I was curious if it only read codes from the compressor and cooling system or the entire AAC, which they claim it does. I had/have no error codes in the Durametric Air Condition section.

I will still take this to a independant shop to figure this out and have them PST2 it. I will then follow up on this topic if they find error codes on the PST2 which the Duremtric didn't pick up.

Obviously the values and additional info the PST2 has (which you shared) is of great use and there may not be error codes but still have a value out of spec that may point to a jammed flap or funky sensor