Alfred B

Question regarding cooling fans on my 996 4S from 2003.

When starting the car, the fans is, obviously, quiet and on low power but as soon as
I start the air conditioning unit, they immediately gets into full power and stays that way during my ride.

Is this correct?

I mean, should the cooling fans go at full speed the whole time while the air con is activated or
is it something wrong with my car?

Mike Murphy

No, the fans should operate at high speed if the AC fluid pressure is >16bar. So something in the AC circuit (the pressure sensor) might be giving a false reading, or else the reading is correct and something is causing high pressure like that.

Does your AC otherwise work normally (get cold)?

Alfred B

Yes, the AC works as it should

996love

Did you recently acquire your car?

Maybe the previous owner jumped the low- and high-speed fan relays. That’s what I did to mine, and my fans run at high speed when my AC is activated.

wildbilly32

Are you sure your engine cooling fans are on low speed when you start the car, because they shouldn't be? Next time you start the car, get out go to the front wheel well and put your hand between the front tire and the front of the fender liner(C4S have the outlet louvers in the fender liner). Do you feel significant air movement? You shouldn't as fans should NOT be running at this time. The cooling fans are fairly loud and should run on low speed when you turn the air conditioner on not when you start the car, unless as mentioned above, a modification has been done.

Alfred B

When I start my car and the AC is off from the start the
cooling fans are off or in low speed and as soon
as I start the air con they immediately turns to full speed

pauldvazquez

My fans were doing the same thing. I replaced the fan resistors. If I remember correctly (and there is a good chance that I am NOT), when the fan relays are calling for low speed (which should be MOST of the time), the power to the fans goes through resistors to lower the amount of power they receive, thereby running at a lower speed. There is a lot of information available in this forum about how to DIY the repair. Once you get into it, the repair is relatively simple.

Doug