85euro928

Sorry for the long post.
I've installed a pair of Spal fans controlled by a Derale PWM fan controller. The controller currently controls both fans together, meaning they start, ramp up, and stop together. They also both come on full when the AC is started. The fans starting together seems to spike the circuit as I've had issues with blowing fuses and currently with what I believe is a fried relay.
After initial installation of the Derale controller, prior to dropping the car off the jack stands, I had the first Derale sensor fail. I then installed the second sensor and found that with this sensor the fans would randomly start with the car off, when the car was dead cold, and usually in the middle of the night (the system is powered from the jump post). Derale tech help chalked it up to having heat in the garage even though the heat was off:/ I've since run the power for the system through a relay to insure that the fans only run when the key is on.
If you do a quick search you'll see that Derale has had reliability issues and it tends to be hit or miss.
As I like to drive the car daily and attend GTGs, which tend to be more than 6 hrs away, I want to see if I can come up with a system that has some redundancy.
My first thought was to purchase another Derale controller and control the fans separately, but that seems to be inviting trouble.
My second idea is to utilize the previously removed aux/pusher fan circuit for one of the fans? In addition to one fan being controlled by the radiator temp, it would also kick on if the intake or AC refrigerant get too hot (which I'm guessing Porsche thought was a good thing).
Thoughts and opinions appreciated.

Petza914

In my 81 Euro S, I installed a switch in the ashtray area where I could activate the fan manually. Would do when picking up food at a drive through, when I wanted more air flow across the A/C condenser when not on the highway, or anytime I saw the temperature start to rise. Worked great and with the manual activation I could engage it before the automatic temp sensor would have so could prevent the higher heat soak that it then had to recover from with the automatic activation.


Here's the push-button fan switch installed in the ashtray




Took these wires off the temp controller switch and connected them to the relay along with the wire from the interior switch




Hooked up the interior switch via an SPDT relay so it doesn't draw the fan power through the switch, just gets the trigger signal and then uses the stock wiring to power the fans




Mounted the relay via a Neodynium magnet

john gill

Based on your description I would think your issue is more with the setup of the PWM controller , this alone should allow the controlled application of full load current , otherwise defeats the purpose of using one .

JG