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Re: A/C question


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A/C question
Ed B - 8 months ago
We took the 00 Boxster S to the parade. Lots o 90 plus temps. On auto setting, A/C always blew cold, but periodically it seems that the fan would drop to low speed. Reducing the temp four or five degrees would eventually increase fan speed. Setting the temp beck to normal,(auto) worked OK until the cycle repeated in about half a hour.
Any ideas? Fan resistor?

Ed B confused smiley
Before you replace fans or resistors check the connections of the cabin and outside temp sensors.
The A/C compares the difference between the two in order to determine when the compressor should engage and how fast the fan should spin.
Happy Boxstering
Pedro

Pedro Bonilla 1998 Boxster 986 - 287,000+ miles: http://www.PedrosGarage.com
PCA National Club Racing Scrutineer - PCA National HPDE Instructor - PCA Technical Committee (Boxster/Cayman)

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Re: A/C question
Ed B - 8 months ago
The outside temp sensor reads correctly on the instrument panel. I'll check the cabin sensor. I was using a V1 and a dash cam. Interference?

Thanks,

Ed B
Re: A/C question
MarcW - 8 months ago
Used a V1 and a Garmin NAVI unit both plugged into the cigarette lighter socket in the dash of my Boxster and these devices never appeared to interfere with anything.

Concurrent with, or shortly after the cabin vent fan speed drop did the cabin temperature feel like it went up? Did the cabin air feel humid?

If so that's a sign the A/C system for some reason had developed what is in my experience totally out of character some kind of intermittent inability to keep the cabin at the 72F temperature.

If not, then it is sort of normal behavior in my experience.

In auto mode with the temperature set to 72F after a while the cabin vent fan speed drops to below the half way mark. The A/C system is very effective at cooling the cabin and once cool doesn't have to work too hard.

Sort of normal behavior... I have to mention that in my experience with my Boxster (and Turbo) the fan speed in auto climate mode (or in any mode) never makes sudden/big drops in speed, although under certain conditions like when starting out with a hot car and cabin as A/C system gets the cabin temperature under control the cabin vent fan speed will come down from high to about half speed over just a few minutes.

On the passenger side of the dash there is a small round grill. There is as least what I understand a small fan there which is used to circulate cabin air over a temperature sensor. This is to let the climate control know the cabin temperature and if the cabin temperature varies from the desired temperature the climate control system will adjust various things -- air flow doors, fan speed, A/C compressor displacement -- to bring the temperature back to the desired setting.

If something blocks this grill this can affect the auto climate control's ability to keep the cabin temperature at the desired setting. The system can react rather quickly.

Or if something was causing cool air from say the dash vent on the side of dash towards the grill opening this could cause the A/C system to believe the cabin air temperature was lower than it actually was and cause it to cut back on the air flow. Thus a drop in the cabin vent fan speed.

Never had to have any A/C work done but my info is the auto climate control system is pretty sophisticated and has some self diagnosis capabilities. If you are unable to find anything to explain the behavior a Porsche tech with a Porsche diagnostic computer can query the auto climate control system's controller for any error codes and from this be able to diagnose what's wrong, if there is anything wrong.
Re: A/C question
Ed B - 8 months ago
When the fan speed dropped, the cabin temp definitely went up. Outside temp was in the 90's. Fan speed bar graph didn't change. Cold air still coming from vents but no volume. Your comment on the passenger side temp sensor is interesting. Wife had her iPhone on
thanks,
a mount on the right vent. We are having rain for a week. I'll test it when we dry out.

Ed B
Which fan?
Boxsterra - 8 months ago
The exterior fans change speed depending on the coolant temp and A/C pressure.
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