McCulla

'05 C2, 30K mi. When I hit the ECO button to start the A/C, there is about a 10 second delay before the system seemingly "kicks" into a different operation mode. The fan is running at the speed I select, but there is a noticable increase in the fan speed (or maybe just the outflow?) when it kicks into the "second stage". The fan is indeed blowing for that delay period, but hot air. I honestly don't remember if this is a new finding (was the cold air/fan speed increase quicker months ago) or if I am just more sensitive to the delay because of our hot temps. Anybody care to weigh in? Thank you!

CamsPorsche

I live in Dubai and all of my mates 911's and mine do the same thing...

You are probably more sensitive to recent heat temps.

McCulla

Thanks camsporsche, Our temps aren't anywhere near yours!!

Kuhan

I suspect (and this is pure speculation) that there is some delay in the a/c workings to make sure that the power demand does not cut the engine out or something like that. I also find that the a/c doesn't kick in immediately on starting the car and it takes a few seconds before it gets up to full steam.

The largest power demand from an electric motor is at start. I bet the delay in start is a power protection mechanism.

GSIRM3

Except for the fact that he says his blower, which is electric, is running when he turns on the AC, and the fact that the AC compressor on a car is not an electric motor. I have noticed the same thing in my 997S and other cars also, mostly with automatic climate controls. My guess is the momentary delay is a result of the auto climate control "brain" needing a few seconds to assess the situation when the AC is activated, and also a possible delay before adjusting the fan speed to allow the compressor to engage and refrigerant to begin circulating. Getting cold air out of the AC is not an instantaneous event. It takes a while for the vapor/compression cycle to begin operating at a level that will produce cold air.

ADias

You say you 'hit the ECO button to start the A/C'. The AC is on by default if you press Auto. IF you press Eco and the Eco LED is ON the AC is Off.

McCulla

ADias, I don't use the auto function, only the "on demand" ECO button, so my A/C is not on by default.

McCulla

....oh, and I am aware that when the LED is lit, the A/C is off.

ADias

The proper procedure is to push Auto, then change settings from that point on...

The AC is only on, when the Eco LED is NOT lit.

McCulla

see post above

winkingchef

This is the answer to your question. The compressor needs to compress the refrigerant and that takes time, whether it is a hydraulic or electric motor doing the work. Being German, Porsche probably doesn't switch the airflow over until the compressor hits temperature.

As a pretty experienced EE, I don't think the inrush current is significant enough to cause a perceivable delay.

McCulla

Thanks everyone. I'll write this off as a lack of awareness on my part before summer temps hit full on. It's all good.