My 03 does NOT run all the time, it does turn on once in while, and it DOES blow IN.

 

mine does not run all time either.. it comes on & off depending on temp...

 

Just visited the Porsche museum in Stuttgart last week and read about all the variants of 911 Turbos. The decklid fans blow cold air onto the engine.

 

Yes, it's a standard Porsche design philosophy.

If someone has a 996 Turbo deck lid fan that blows air out of the deck lid, it's either not OEM, or it is OEM and was wired wrongly by mistake.

I've e-mailed my friend at PCNA to ask about the GT2 and GT3.

 

I'm not convinced (although I'm getting there) we have enough information to say it's the wrong way - I can say that with the OEM fan and decklid, it blew out from the vents.

 

Sad

 

Being as it's getting hot down here in the Sunshine State, my fan has been coming more frequently as of late--2002 and my fan draws air IN toward the engine compartment...guess it works the way it's supposed to

 

my 2001 pulled air into snorkel/engine bay in OEM form. Installed the mashaw harness and this reversed it. noticed IATs went up noticeably in stop and go but on highway difference isn't as noticeable.

Had always wondered about water. after taking apart the decklid lining and snorkel to get to the harness (hydraulic wing failure), had a chance to understand the system and have a theory. the snorkel has a gap around it. Would have been just as easy for porsche to make this air/water tight. with the deck lid down, the liner serves as a funnel. I think that gap and the fan flowing in (sucking) are paths of lesser resistance for water to pass as opposed to entering the airbox.

By way of sucking in ambient air to the engine bay, (exiting bottom side) the "funnel" and snorkel are filled with ambient air. If the air blew out (reverse) the snorkel is being fed hot engine bay air.

will reverse the wires tomorrow and see if IATs change. Does anyone know what sensor/parameter sets off the fan?

 

I spent a couple of weeks trying to figure out if the fan on my '03 was supposed to be running all the time (whenever the engine is running), as there is a lot of conflicting info on this. My fan was in fact running at a "low" state whenever the engine was running. It would come on on "high" whenever the engine compartment got heat soaked (as is normal).

The Readers Digest version is this (at least for an '03): The fan will run continuously whenever the engine is running IF you have a fuse in location C5 of the fuse block. Fuse C5 gets voltage from the fuel pump, whenever the fuel pump is energized (engine running or key initially turned on). There is a resistor (or regulator) that drops the voltage to 7 VDC, and the reduced voltage (from 12 VDC) is the reason the fan runs at a "low" speed. If you trace the Porsche wiring diagrams, this is how the purge fan is wired. HOWEVER, fuse location C5 is shown as "optional" on the wiring diagrams. Also, in my factory owners manual, as well as some other fuse diagrams I have found, there is NO fuse shown at location C5. Thus, if you don't have a fuse in C5, your fan will only run on "high" when the engine compartment gets heat soaked. Non-turbo 996s do not have the fuel pump wiring interface on the purge fan, so the fan does not run at a low state whenever the engine is running. I suspect (although I have no wiring diagrams for the GT3) that the GT3 purge fan set up may be the same as the NA 996.

And the answer to the original question is that while Porsche calls it a "purge fan", it is supposed to suck air into the deck lid, not blow the air out.

R-

Bill

 

great info bill, thanks

just reversed the wires, no splicing required, just carfully remove the connector cap, slide a small flathead in the groove under the pin and pull it out, reinstall reversed.

IAT to ambient gap reduced on avg from 10-20+ to 5-10+ mixed street driving / intermittent WOT to redline.

 

On my 2003 TT, The fan pulls air from the engine compartment UP into the air, so it scavenges the hot air away from the engine.

 

Then it's not operating the way the factory designed and built it.

 

I am not sure (BTW the fan only works if the engine is hot, including after the engine has been switched off) but as I said, they move a lot of hot air away from the engine. Do a search, you will find that other Porsche folks have the same, some blow, some suck :-)


check this thread https://www.6speedonline.com/forums/...ow-poll-4.html

 

Think about it...Would you pull the air from a hot exhaust and engine block into the engine compartment or pull fresh air from outside into the engine compartment....The fan modulate on and off depending of engine compartment temperature to keep it below 172F...And the monitoring is still happening up to 40 minutes after shut down....(Porsche 996 the essential companion from Adrian Streather)

 

I dont use my fan at all. My tial bov is in the way