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AC - air conditioning fan speed problem?


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I'm looking for any suggestions, 1st hand experience or not in trying to figure out what to do re: this issue.  Lately it seems that when I hit the auto button on the air conditioning, the fan speed does not seem to increase to where I am accustomed to seeing it go in order to cool the car.  In other words, in a hot cabin after hitting the auto button, I used to see the fan increase to maybe 75 or 80% with the temp set to 73.  It now goes to maybe 50% or less and then I have to increase the fan speed manually.  The system does cool just fine if I do the adjusting(fan) manually.  Another thing I've noticed now is  when I put the AC in re-circulating mode, the fan speed decreases while all the times before this it use to increase speed after going in re-circulating mode. I'm trying to figure out what the problem may be.  Thanks!

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Please note that this is only guess work on my part, but if this was a BMW I would put money on the fan within the climate control unit that sucks air in from the cabin and blows it across the temperature sensor internal to the controller to provide temperature feedback to the control circuitry. I guess Porsche works the same? It does have a slotted vent between re-circ and ECO buttons is this blocked? As I say, just guessing. Best of luck.

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Don't know where those parts are but again assuming similarity to BMW item 17 is known as the hedgehog! and symptoms of its failure is a fan that will not retain a constant speed but instead pulses from slow to fast to slow etc. Personally I would try item 15 first.

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Have you tried to scan it with Durametric for any error codes and any real-time sensor values on the climate control unit?

Hey Ahsai - I don't have the Durametric tool unfortunately.

 

I'm still looking for some help on how to access the ac components in the footwell - I think that's where there located.  All I can find are the parts schematics but I need know how to access them.

 

Anyone who can provide some directions?  Tks!!

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The assembly lives behind the glove box and you should be able to access part of it with the lower cover removed

http://www.pelicanparts.com/techarticles/Porsche-996-997-Carrera/103-ELEC-HVAC_Motor/103-ELEC-HVAC_Motor.htm

 

You will see the blower motor so you can orient yourself using the diagram you posted for the rest of the components.

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  • 8 months later...

can anyone verify for me that when the cabin is at or near the desired temp setting in auto cool and then recirc is selected, that the fan speed increases to cool cabin quicker?  The clip shows what mine is doing now - it actually decreases speed whereas before, it used to increase speed to cool quicker.  I have a 2006 model year.  Tks

IMG_0027_2.mov

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  • Admin

can anyone verify for me that when the cabin is at or near the desired temp setting in auto cool and then recirc is selected, that the fan speed increases to cool cabin quicker?  The clip shows what mine is doing now - it actually decreases speed whereas before, it used to increase speed to cool quicker.  I have a 2006 model year.  Tks

 

If you go to the Porsche Technik book for the 997 S - the HVAC section starts at page 128. (as a Contributing Member you have access to that here)

 

It will tell you trigger conditions that change air flow and damper settings. If it is not operating within the airflow triggers then you could have a damper (flap) that is hung up or bad.

Check the conditions and if you still feel it is not performing correctly then get a PIWIS or Durametric and run through the HVAC diagnostics.

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Tks for the link. A lot of good info. Dealer says no error codes and all is normal. Just don't understand why the fan speed use to increase and cool the cabin faster instead of now decreasing speed.

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The fan continues to decrease speed when put in recirc. mode while in auto cool.  Even though the dealer says this is normal, it is opposite of past experience - the fan use to increase speed.  I decided to call Durametric and ask them a couple of questions of what parameters are measured in relation to the a/c.  They told me that there are too many parameters for the ac and the only thing that will be picked up is if there are any error codes and that the software will not read/show actual values.  So, here's my question - 2 of the parameters that are measured for air throughput are vehicle speed and fan voltage - so is it possible for either one of these or any other parameter to be not within spec but still not throw an error code?  I just don't understand why the fan is not working the way it use to and that the dealer says it's normal for the fan to slow.....???

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I just tried mine today ('03. 77F ambient and temp set to 72F) and my fan did decrease its speed in recirc mode.

 

Maybe the only exception is when you get into a warm car and turn on the a/c first, then enter recirc. The fan may then increase speed. I have to confirm that though but I seem to remember that's the behavior.

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I just tried mine today ('03. 77F ambient and temp set to 72F) and my fan did decrease its speed in recirc mode.

 

Maybe the only exception is when you get into a warm car and turn on the a/c first, then enter recirc. The fan may then increase speed. I have to confirm that though but I seem to remember that's the behavior.

tks for checking.  guess I'm going crazy???

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I just tried mine today ('03. 77F ambient and temp set to 72F) and my fan did decrease its speed in recirc mode.

 

Maybe the only exception is when you get into a warm car and turn on the a/c first, then enter recirc. The fan may then increase speed. I have to confirm that though but I seem to remember that's the behavior.

tks for checking.  guess I'm going crazy???

 

If I happen to come across a case where the fan speed increases in recirc, I'll let you know.

 

And yes, you may be chasing wind :)

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BTW, my explanation is like this. If the outside is hotter than the cabin, recirc should make the fan decrease as the a/c will only need to cool the cabin air as opposed to the outside hotter air. The reverse is true if the outside is cooler than the cabin (e.g., car parked under the sun for a while).

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