Fans: to be two or not to be two

curtisr · curtisr's Garage

I hate seeing the temperature guage read right of centre even a little and am thinking about how nice it would be if both the rad fan and the AC fan came on when the rad fan is activated. That way, I keep the temp left of centre and all's well.

At the present time, the AC works.

So, I was wondering if:

a) I should forget about the whole thing
b) twist the fan wires together
c) install another relay and make the appropriate connections (what they are yet I do not know but they shall be the wonders of the earth) to activate the AC fan at the same time as the rad fan, or
d) do something else that I didn't think of.

Thanks.

Roger

v2rocket_aka944 · 04-17-2014, 12:27 PM

i have the low-temp fan switch (but a big single fan) and my temperature never ever gets to the middle.

nightheart · nightheart's Garage

did you try a lower temp fan switch and a lower temp thermostat? This will kick your fans on sooner.

flash968 · 04-17-2014, 02:34 PM

i didn't know the 944 fans were set up like that. on the 968, both fans come on at the same time, and both have 2 speeds.

perhaps some rewiring might allow you to convert your setup to the 968 setup. seems it would be pretty simple.

nightheart · nightheart's Garage

It probably wouldn't be hard to change it, but the stock setup works fine. As long as everything is working with the cooling system. Even running lower temp sensors isn't really necessary. The stock setup for an early is each fan has 2 speeds. First the rad fan kicks on then if necessarily the a_c fan kicks on. I'm running stock sensors and the only time my car got close to overheating was when the fan temp sensor went bad. Even on 100+ days in the summer sitting in traffic. Each his own, but its not really necessary to reinvent the wheel.

v2rocket_aka944 · 04-17-2014, 04:28 PM

its very easy to do, my car is wired to function the way you are asking for.

grab the high-speed (PS) fan plug and put some quick-disconnect terminals in the plug. run these wires to the coil posts of a 40A relay. run a fused 10-14 awg wire from the battery to the power side of the relay and then run a wire from the output post to the fan motors +, and another wire from the motors - to the chassis of the car.

that way the factory fan circuit only sees ~150mA through it and both fans are slaved to the high-speed function.

djnolan · djnolan's Garage

If the temp creeps up to 2/3 while idling in traffic, no big harm. The fan should kick on and bring the temp back to 1/3, before any damage is done to the engine if it is working properly.

On the road when the engine is at a higher RPM, the temps should drop down to 1/3 or so after a few miles as the air rushes thru the radiator.

If this is not happening it is not a cooling fan problem. It is a problem with the cooling system, such as a clogged radiator, coolant leak, low coolant, bad thermostat, bad radiator cap, etc. More rarely it is a bad water pump or clogged engine cooling passages.

The cooling fans are only there to assist in cooling when in stop and go driving or when the A/C is on. The car should not need the fans to run cool when moving on the highway.

Take it for a test drive on the highway for about 10 miles, and if it doesn't cool down to 1/3 (or so) then you have a cooling system problem and not a fan problem.

curtisr · curtisr's Garage

Thank you one and all for your input, guidance and patience--no sooner than I had finished posting this my Internet decides to quit.
I should learn to live with the accuracy that the temp gauge is and the idiosyncrasies of the Porsche cooling system. Yes, it's 2/3 in stop and go traffic and 1/3 after the fan comes on. Still, the two fan set-up with relay appears to be within my grasp and I hear her calling to me...

mattdavis11 · 04-19-2014, 05:57 AM

The operation of the fans is something I plan to address as well, but I want the fans to turn off when air flow through the condenser and radiator due to speed is sufficient.

nightheart · nightheart's Garage

Quote:

Originally Posted by mattdavis11

The operation of the fans is something I plan to address as well, but I want the fans to turn off when air flow through the condenser and radiator due to speed is sufficient.

I contemplated hooking up a toggle switch to kill power to the fans for use at highway speeds. I never did it, because I know I would forget to flip it back on after getting off the highway. Definitely upgrade to the 5 blade fans, if your still running the 3 blades.

CHICKS · 04-19-2014, 10:19 AM

I say leave it alone, as it's normal function of the cooling system.

curtisr · curtisr's Garage

Quote:

Originally Posted by nightheart

Definitely upgrade to the 5 blade fans, if your still running the 3 blades.

I'm all over it. Thanks again to all!

curtisr · curtisr's Garage

Quote:

Originally Posted by nightheart

did you try a lower temp fan switch and a lower temp thermostat? This will kick your fans on sooner.

I wondered about this. In fact I called a popular parts supplier and he said the controls for this was all in the ECM and not the temp sensors.

Who's right???