Cooling Fan "On" a lot

[MNBoxster]

Originally Posted by babur

Hi guys,

Along the same lines, my 2001 Boxster is making a very loud noise coming from the passenger side air vent while the A/C is off. It doesn't sound like a normal fan noise.

Does anyone know anything about it.

Thanks

Bob

Hi,

I suspect what you may be hearing is the Shut Off Valve actuating and air rushing in to the Fuel Tank. This air is brought into the Tank through the hole that is located by the gas cap. This is actually normal. It is required for proper operation of the Fuel Tank Venting system and the Mass Air Flow Sensor.

The Shut Off Valve opens or closes depending on the load state of the Carbon Cannister. What you hear is the Shut Off Valve actuating, and many people have mistaken this to be a noise from the AC system.

On the 987, this was changed to a different design in the Tank Venting System. This system uses a DM-Tl (Diagnostic Module - Tank Leakage) Valve Assembly. This Valve draws fresh air from a filter and is located on, and integral to, the Carbon Cannister as a package. The change in its location, and operation, eliminates the venting sound. Hope this helps...

Happy Motoring!... Jim'99