Engine Compartment Fan Question

I was out driving for about 40 minutes today in 92 degree weather and when I got home and shut off the engine I noticed the fan in the engine compartment was running. No error lights on my dash and everything was fine while driving. The engine temp was just over 180 the whole drive. I parked it in the driveway in the sun. I've had other cars that have had the fan cycle on and off after a drive and with the car turned off? I'm just checking to see if this is normal for a Porsche. I thought I read somewhere that the fan will cycle on for up to 30 minutes with the ignition off but I can't remember where I read it. Any insight would be appreciated.

Totally normal

^^^ Yep. Normal. I think every person who buys a 996 wonders about that after their first drive or two.

Thanks guys! I've had a few other cars that have done this but since this is my first Porsche and car of any kind with over 100,000 miles I'm being extra cautious. I'm sorry to say this is just the first of many questions that I'll have.

I have never heard mine run.......I hope it is functioning properly. Is there any way to force it to run without a Durametric to turn it on. Thanks, Ray

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Yes, pull the plug on the fan wire off and hook a 12v power supply up to it. The controlling temp sensor for the engine bay fan is a small probe that is attached with a rubber grommet between the two closest intake runners on the passenger side bank. The sensor heat probe detects the ambient heat rising off the engine and the fan starts up using battery power (when ignition off) to run the fan until the preset temp (can't recall what it is) is below the threshold or x number of minutes since engine was running. FYI: Durametric's can't turn the fan on or off - only tell you the engine bay temp's.

So if the fan is running with ignition on, when the ignition is turned off should the fan continue running?

If memory serves, Durametric can turn the engine fan on/off. It can also turn on/off the radiator fans and SAI pump, and fuel pump, etc. You can probably test the fan by using a hair dryer to blow hot air on the sensor. When engine is turned off, the DME still keeps monitoring that sensor.

Correct , you can turn on the engine compartment fan with the Durametric

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Not all ver's can do this. Only 6.0 and up can do this for 98-05 996's. Fault code for purge fan is P1675 From Renntech Engine Compartment Purge Fan To reduce the temperature of the engine compartment, a fan actuated by the DME control unit is installed under the ventilation grille of the engine cover. If the fan is active, fresh air is fed into the engine compartment. The fan can only be actuated 100 seconds after the engine has been started. Functioning 1- With engine running or ignition on: If the engine temperature is higher than 102� C and the engine compartment temperature is higher than 60�C, the engine compartment fan is switched on for 30 seconds by the DME control unit and the engine compartment is thus ventilated. 2 - Engine compartment fan if vehicle is stationary and engine is switched off (after-running of control unit): If the engine compartment temperature is higher than 60� plus C when the engine is switched off (ignition off) or if the engine stalls (engine speed: 0 rpm), after-running of the DME control unit lasting 20 min. begins. The DME relay remains active. After-running of the fan continues until the programmed time has expired (20 min.) or until the next engine start after which the engine runs for more than 100 seconds. If the engine compartment temperature is higher than 84.75� C during after-running of the control unit, the engine compartment fan is started and runs for 30 seconds. If, at the end of the operation period (30 seconds), the engine compartment temperature is still higher than 84.75� C, the engine compartment fan is started and runs for another 30 seconds, etc. If the temperature now drops below the threshold (84.75� C), a polling pause lasting 10 seconds occurs. Note: If the engine temperature has not dropped below 80.25�C after the engine compartment fan has been running for 25 seconds, a fan fault is registered and the coolant level warning lamp is activated (flashes)."

In response to OP of where he read it - it's in the owner's manual.

Take the engine compartment sensor off the manifold and lay it close to the engine while driving. That'll set the fan off. It will also cause your coolant warning light to flash bc it's indicating the compartment temp is to high. I removed my fan bc as some of you mentioned it hardly comes on. The stock gt3 doesn't even come with one if my memory serves me right.

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Depending on what your comparing - the GT3 engine (M96/76) is a highly modified vers of the M96/01 - M96/02 specs as found in the 99-05 C2 and C4 models and is much closer in design to the M94 then it is with the normal Carrera engine. (all sorts of cly treatment differences, material type changes) There were all sorts of cooling changes incorporated as the car was homologated for racing based upon the equipment delivered as spec. A third rad was added up front, (59% more cooling surface) oil/coolant heat exchanger is larger then the 01/02 engine types, larger diameter exhaust (45mm) pipes and less back pressure from the cat's (shorter length and a new tri metallic layer) along with a different dry sump set up with a larger oil tank at the front of the engine all helped reduce heat in the engine bay and then there is that rear deck design that flows far more air into the engine bay for intake purposes and heat reduction. That's why that little fan getting in the way had to go and wasn't needed anyway. It's only required for a car that puts out 100hp less!! (Go figure.)

I know this is an old thread but after searching it seemed the best place to post. It was 100 degrees today and I was in traffic a lot. Pulling into my garage the Engine Compartment Fan Failure came on but the fan was running fine. The engine compartment temp gauge looks to be in place. Running temp is normal, coolant is fine but one thing that seemed odd, the fan is pushing air out of the compartment up through the spoiler, shouldn't it be pulling air into the engine compartment through the spoiler?

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I've put my hand on on the spoiler a couple times while the fan is running and it's definitely pulling.

polarity switched on the wires?

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Sounds like it.

I didn't see any cut or spliced wires at first look. I will take a look when I get home tonight so see if the plug was some how installed backwards. I guess the previous owner could have installed a aftermarket fan which is why it is blowing instead of sucking. .

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Not necessarily. The fan puts out a goodly amount of air and some can be directed by the less than aerodynamic shape of the engine out of the engine compartment at seemingly odd places. Through the spoiler for instance. I bet had you checked you would have found a goodly volume of hot air flowing out of the bottom of the engine compartment. When my Boxster's or Turbo's fan is running I can feel the hot air rising from around the rear of the car as the engine compartment is blasted with air from the fan.

I had to run out at lunch today and when I got back to the office, the fan was running so I opened the engine lid and disconnected the fan so I could actually see which way the fan was spinning. It is trying to pull air out of the engine bay and exhaust it through the engine lid vents. It isn't blowing air down into the engine bay as I didn't feel any air coming out the bottom of the car. The plug only clips in one way into the fan so if it is reversed it has to be somewhere else, I will have to investigate further.

Is your battery connected in in the correct polarity?

I thought the fan drew air from below and pushed it out the top, but my memory could be flawed. Running the other way would be fighting physics - trying to force warm air down instead of pulling it up...

My fan, the one time it actually went on did push air out of the rear spoiler IIRC. I think that is normal.

http://www.6speedonline.com/forums/9...flow-poll.html There was a TSB on this for a few Carrera's with Aerokits. The purge air fan in the engine compartment had the wire polarity reversed on the plug connector. On the these cars the fan incorrectly blew hot air out. (The fix is relatively simple as you just reverse the pins on the fan plug.) The correct function is for the fan to draw in cool air. You can test this (when the fan is running) by holding a sheet of paper between the spoiler and the engine compartment lid in the area of the ventilation slots. If the fan is functioning correctly, the sheet should be sucked on to the engine compartment lid. -------------------- Loren RennTech.org PCA member since 1978

That was also my observation. Thanks. Now I feel better.

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Thanks for the info fpb111, mine forcefully blows the paper off the deck lid. Hopefully I can get the pins out of the plug without causing damage, I unfortunately do not have a rectangular pin tool.

maybe a little overkill, but these should help... http://www.ecstuning.com/Porsche-199...ronic/ES11414/

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Hmmm. I'll have to check mine again. I didn't know about the TSB

I've only heard mine come at start up, for just a short time, never after motor shut off, & it's hit 105 here recently?

Thanks for the note about the TSB. I'ma fire up my fan with Durametric and see if Megamaid is set to suck or blow.

Pins were easy to get out of the plug gently using a small pick. I reversed the polarity and it is sucking air. I am surprised by how much air movement I can feel underneath the rear end of the car.

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Now you know for sure if she sucks or blows.

How can you check to see if your fan is operating properly without a Durametric? I just ran a blow dryer on high on the sensor probe while the engine was idling at 180� and the fan never came on once. I don't recollect ever hearing it operate since I've owned the car and we have some damn hot weather here in DFW.

it looks like some of the aftermarket folks are confused also. "So I get an error message on the first hot day of the year with me in the car...engine cooling fan potential failure. I go back and notice it is spinning fine, heat sensor is in place, coolant level is normal/correct, no cracks, but the air is now blowing up and out...pre-new harness it was blowing in "I think." So I called my harness vendor. M.A. Shaw. Super guy. His harness is 50% of OEM and of the same quality. It is very, very high quality. Perhaps better than OEM. He happened to have gotten an email from me on this subject yesterday and had lunch with four Porsche mechanics and they all told him on the 996TT the air blows out. So, I wanted to know if you guys could help me out and say if the decklid air fan blows in or out...probably best to check after a drive when it is idling...it is not very efficient so you can be fooled but a piece of paper over the vents makes it pretty obvious either way. Mr. Shaw suggested maybe Porsche changed things year to year. Hence the format of the poll is by year and in/out. Needless to say, my error message went away with the new fan direction (I cut the harness, spliced, and heat tubed it last night). And the fan ran "less long" after driving... It could be another issue with my car, but this question comes up from time to time and I'd like this thread to be data for the rest of the board to use. Just think of the fabspeed cold air kit...it says the "fan blows cold air directly at the filter".....but I want to be sure as he feels 4 mechanics are telling him the opposite. It makes little sense to me that you'd draw the air past the manifolds, turbos, and exhaust. But, I suppose this does let more water into the engine (not something Porsche seems to be worried about historically)."

On my TT, it sucks air from above and blows over the engine. Last week, it was pretty hot here and after I pulled into the garage and shut off the engine, I heard the fan run. I put my palm over the rear vents on the deck lid and I could definitely feel air being sucked in. I always had thought that the air would be blown up to remove the hot air (since hot air rises), but I guess, the air to be sent down if you are driving (aerodynamics reason?) and the fan needs to run.

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I think you are talking about the SAI pump. We are talking about the vent fan on the deck lid.

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Figured it out. If you unplug the harness at the base of the temperature sensor while the engine is running (mine was at 180�F) then the compartment fan will come on after about 3 seconds.

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Thank you, you are probably right. That means my fan does not come on I guess.

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^Same here^ Maybe not as hot as DFW but I've never seen or heard my engine compartment fan operate. This being said, my temp gauge has never climbed above the left edge of the 0 in 180 either (I figure the temp to be around 190 - 200 degrees F ?)... We've had ambient temps between 85 - 90F this summer, so she warms up pretty quickly...

It's very seldom that the purge fan goes on. With my MKII aero wing (which allows for a lot of airflow when the car is off), the fan may have gone on a total of 2 or three times over the past 3 years. I've definitely turned it on more times with Durametric than it's run on its own. So...I wouldn't start throwing parts at the car if you're not hearing the purge fan come on after a hot drive.

My fan comes on quite a bit with temps in the mid 90s here in the Raleigh, NC area. Since I switched the polarity to be correct it doesn't run as long but if I am in bumper to bumper traffic it comes on. I have a tiptronic trans so not sure if that has anything to do with it or not, do the tips produce more heat?

Well, mid 90's is about 15 degrees hotter than what my 996 is used to - so I can't say if it's the ambient temp or the tiptronic...

"So...I wouldn't start throwing parts at the car if you're not hearing the purge fan come on after a hot drive." I don't know if you're specifically responding to me or not... I've had the car since Oct. '14, so no I don't plan on throwing parts at it - more like trying to figure out if the fan does indeed "work"...Like I said previously, I believe the engine temp is within a "normal operating range" so it's not like I'm freaking out about it - just wondering... Thx

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Either trigger it with Durametric or run a hot lead to it from the + jumper point in the engine compartment. Florida high 90's, hot, and the purge fan hardly ever runs...but I know it works.

Yeah...no Durametric here yet... I'll try the "hot lead" test just to ease my mind

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Are we sure about this? This poll is from the Turbo/GT2 forum. My fan kicks on almost after every drive. It is between 70-85 here in the recent weeks. Is it normal to always come on?

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And? My 2004 turbo comes on almost every time after a ~1hr run when the temp is above ~75. Sometimes twice just like the manual says.

Mine never comes on. But I�m also about to install a manual override switch.