Macster

I assure you I don't make things up.

But I have to agree it sounds nonsensical.

I wish I had not posted that bit of info until I had the source of my info at hand. I am actively looking for the reference from where I got this info.

mdd

Sorry Macster, I didn't mean to imply that you made it up. Just that wherever you heard or read it from was likely a questionable source. Would be good to track it down somehow. Lots of nonsense on the web posted by well meaning folks.

up4speed

For the fan to run after a shut down, it has to be hot outside. That is solely determined by the sensor in the engine compartment. If yours ran, that part of the circuitry is working as it's supposed to. You can check it to make sure if you want. After a drive, shut the engine off, open the engine cover and use a blow dryer to heat the sensor. The sensor is right under the thick hose on the right side (the turbo intake). If you point the dryer just below that hose standing at the rear of the car, you will warm the sensor enough where it will kick the fan on after a minute or so.
The part that concerns me is that yours won't turn on with the engine running, whether it's cold or hot. It seems like you need to troubleshoot it especially since you have the C5 fuse installed. Maybe the fan is bad (that's easy to check with the hair dryer), maybe the fuse is bad (easy to check) or maybe the relay is bad.
As far as the tune goes, I wouldn't expect a tuner to keep the fan off. If anything, they would make it continuously run. Generally you want things cooler when it comes to getting better performance.
You definitely don't want everything cooking in there, so I would definitely check it's operation and fix it if it's broken. A fan that's stuck on won't cause any other problems, but a fan that's stuck off can cause other heat related problems.

"02996ttx50

my fan doesn't run continually. only when it's hot but usually within 2 mins of shutdown it'll go on for a few mins and if its REALLY hot, it'll go on..then off.. then go back on for another few minutes.

but it doesn't run continually. near as i can tell lol

Daytonaman

Thanks Mr 4speed; fan tests ok. Might be the sensor tho. I'll look for it and try to jump it out. Another issue discussed here was which way the fan should blow. The blade geometry would determine that, although some were wired backwards..

Macster

My recollection is the source was something a senior Porsche tech printed out for me, as I raised this fan operation question to him when I noticed the fan running all the time when the engine was on. It may have been doing this since I bought the car but I was not aware of it and noticed this after I had the car in for the engine compartment lid not working properly.

It turned out that in removing the fuse to disable the spoiler, because the spoiler hydraulics were leaking and the spoiler was operating properly, this fuse also controlled the engine compartment lid circuit, and this accounted for the non-operation of the engine compartment lid.

My thinking was the techs in going after this behavior something was done with the electrical system -- maybe a temperature sensor left unplugged? -- that caused the fan to run all the time.

But it was clear from what I was given the fan operating all the time the engine was on was an intended mode of operation controlled by the fuse I mentioned earlier.

Macster

The engine compartment fan should blow air down.

This causes the hottest air -- around the turbos and exhaust -- to exit the engine compartment area without exposing the engine compartment hardware to the heat from these components.

And opening the engine compartment lid in the belief this results in better/faster cooling of the engine compartment is ill-advised.

Leave the lid closed and let the engine compartment fan and its controlling circularity do what it is intended to do.

powdrhound

I always thought the engine compartment fan blows air out of the compartment, not in. Heat rises and you'd think a fan blowing out would evacuate hot air thus drawing cool air from the cool road surface part of the engine compartment. Looks like all the fans on 911s do blow into the compartment though..

"02996ttx50

it seems counter-intuitive but they definitely blow down into the engine comp. i notice this the few times i am covering the car and the fan is still on.

rmc1148

At speed might be to much air pressure to blow out? But agree it seems like that would be better set up

993GT

every 911 since day one is air in from top, air out bottom.
a great solution for track/hardcore cars would be to vent the deck lid to let the air out above the bumper...should reduce the 'vacuum bubble' behind the car and reduce the airflow pushed under the car, less lift in theory..

mmm951

Macster is on the money. It does not make sense to draw up hot air from the headers/exhaust into the top of the motora s it will increase the temps in the engine bay.

I had a similar issue in that my car kept giving me an engine compartment temp message. I knew everything in the cooling system was fine and realized the fan was blowing up instead of down. I have an aftermarket fixed wing in which the wiring was not done correctly. I simply reversed the wires and never had a problem since. Also, my car was exhibiting similar symptoms to that of the OP - the fan always seemed to be running even when cold.

993GT

^beyond thermal reasons, it would be better to suck air from the bottom to top for lift/.d.f. reasons....my fan runs full-time, and should be better for it, reasoning being better airflow/cooling for all the coldside and post-intercooler plumbing....I want to wrap my pre-turbo airbox and plumbing

Macster

The overriding reason for the fan to blow down is to minimize the risk of thermal degradation/damage to the engine compartment hardware from the extreme heat of the hottest engine compartment components located towards the bottom of the engine compartment.

Thus the fan should blow down to get the heat out and away from the engine compartment.

If the fan was rewired to suck air though and then out of the engine compartment the fan would be pulling warmer (hotter) air past the very components most likely to suffer from exposure to excessive heat but past/throgh the fan as well.

If one doesn't care about the engine compartment components at least think of the fan. It would run hotter and likely suffer from a shorter service life because of this.

Besides, even with all the Turbo (and other models of cars) engine compartment fans blowing down there is a real scarcity of any reports of any engine compartment fan failures so even if the fan is working harder to blow down vs. suck up (which I'm not even sure is the case) fan failure reports don't back this up.

This it is not a concern at all that the fan blows down and I would not rewire my car's engine compartment fan to change this direction of air flow.

993GT

absolutely agree