lost it

HI

I have an early 996 and have a quick question regarding Fan Operation.
I undersatnd that there are 2 fans in the front and one in the rear spolier. The question is how do these operate, if we take the front radiator fans first; do they operate sequentially (IE one starts up and then the other kicks in if cooling is not adequate) or is it both start up at same time ?
Under what circumstances does the rear cooling fan operate ?

I have read every post on cooling and fans and cant seem to glean the information from there so was hoping for an answer from you erudite people.

1999Porsche911

The front fans operate at the same time, either off, low speed or high speed. Both are coolant temperature sensitive. Fans will turn on regardless of temperature when A/C turns on. The engine compartment fan operates based on both coolant temperature and/or engine compartment temperature. The fan s designed to suck air INTO the engine compartment when running. If the coolant temperature gets above a predetermined temperature, this fan will operate, or if the engine compartment exceeds it's temperature threshold, the fan will operate. The coolant and temperature of the engine compartment are monitored even after the engine is turned off and both front fans and engine compartment fan will turn on if temperature limit is reached.

Tbred911

Jim,

what was that test to determine if the engine compartment fan is indeed operational?

1999Porsche911

Warm up your car and then just pull the 2 wire connector off of the sensor which is located between the passenger side 1st and 2nd intake runs. The fan should start immediately and then stop when you reconnect the cable.

99firehawk

you would have a dash warning if the engine fan wasnt coming on

jumper5836

I had a blown fuse and my light never came on under normal operating conditions, until one day in stop and go traffic during a heavy rain storm and a very hot/humid day.

1999Porsche911

The fault will only light up if it is a totally open circuit or if the fan does not activate WHEN REQUIRED. Since most driving conditions never acivate the fan, you would have no warning that the fan motor is inoperatable.

roger's 2937

I live in a farly remote area in Az. and when I'm on a dusty road and come to a stop the fans blow dust all over the place. Is this normal?

Roger B.

AsianImage

aaah...I didnt know the fans turned on when the AC was on. I was kinda wondering why my temps went down when I had the AC on! hahaha...

I did your fan mod..so I have the switch to turn them on whenever I want..but lately on my drive to work...sitting in traffic...I close up the windows and turn the ac on...and then I notice the temps drop! Now I know why!

lost it

I wonder if this is different for Euro cars, when i asked the local porche specialist he was adamant that it was sequential, one comes on and then the other.
In my opinion that sounds a bit suspect as why would you bother spending the money on the extra engineering neccassary to achieve this, and im leaning towards both should come on, but its hard to ignore the official porsche service center. (they never get it wrong he says tongue firmly in cheek),.

Loren

From the 1999 Porsche Carrera Service Information Book
There is only one control line (via the DME) so they switch on together.

Chuck Jones

Roger: In answer to your question...yes....the front fans will blow dust all over....best to try to go fast enough so that you don't get the dust in the front....but then you get it all over the engine compartment. Pave your access road...

carpundit

Gratuitous note: this is the best car forum I've ever seen. The information here is amazing, and well worth every penny of the membership fee.

Thanks Jim, Brad and Loren for the information about the fans, which I can't imagine having found anywhere else.

rountreed

Wow after years of ownership I learned something new!

white out

Awesome write up. Thank you!