Manual control of 3.2 oil cooler fan via existing fog light circuit / dash switch

[famoroso]

Greetings all,

I have always wanted the ability to manually control the oil cooler fan on my late 3.2 Carreras, but I didn't want to add extraneous & unsightly / aftermarket wiring if I could avoid it.

Many Pelicans are aware that the 3.2 oil cooler fan temperature switch has a set point of 245° F...

https://forums.pelicanparts.com/porsche-911-technical-forum/1039954-lower-temp-switch-3-2-oil-cooler-fan.html#post10876986

Per the above thread, I know that you can install a lower temperature switch, but I didn't want to go through the pain and suffering of dropping the oil cooler.

What I wanted was an easy, and clean way to implement manual control (for premptive use before heading up the Grapevine on I-5, or sitting in summer traffic, etc.). In my case, I deleted the fog lights in favor of a Club Sport style front valance, so the fog light wiring, relay and dash switch were just sitting there doing nothing. The passenger side fog light harness terminating ~6 inches away from the oil cooler fan wiring in the frunk (white connector is for temperature switch and black connector is fan motor power / ground). Hmmmm... It felt like serendipity.

After consulting / confirming with Dennis (Timmy2) that the fog light circuit could handle the oil cooler fan electrical load (the fog light wiring and oil cooler fan wiring appear to be the same gauge), I decided to build a short jumper harness, using the OE female two pole connector (technically, a Kostal 9622/1 Mercedes piece) that allows you to connect the passenger side fog light wiring to the oil cooler fan motor wiring cleanly and easily. This allows you to use the fog light dashboard switch to manually control the oil cooler fan. The jumper harness installs / uninstalls in a matter of seconds. Here's the photo essay:

Before...



The jumper...





During...



After (original body side oil cooler fan wiring / connectors tucked up across the top and zip tied in place)...





My next steps are to find the fog light relay trigger wire in the fuse box and move it to a different fuse that will energize the fog light switch regardless of headlight switch position. I'd also like to find a fan pictogram / insert for the dashboard switch itself (to replace the front fog light pictogram).


If I still had fog lights, I would have just gone with a simple switch and two wires that jumped the body side white two-pin "Molex" connector in the frunk.

[Fleetwood]

Did you ever determine the fog light relay trigger wire in the fuse box and move it to a different fuse that will energize the fog light switch regardless of headlight position?

I'm stepping thru the elephant cooler install on my SC and like you, deleted the fogs for a club sport valence look, and plan to use the fog light switch to control the cooler fan. At this point, no thermostat control, manual fan switch only. But I'd like it to work without the lights on. Seems like the brights caused the fogs to go out too??

Thanks ahead for any info or guidance

[famoroso]

Originally Posted by Fleetwood

Did you ever determine the fog light relay trigger wire in the fuse box and move it to a different fuse that will energize the fog light switch regardless of headlight position?

I'm stepping thru the elephant cooler install on my SC and like you, deleted the fogs for a club sport valence look, and plan to use the fog light switch to control the cooler fan. At this point, no thermostat control, manual fan switch only. But I'd like it to work without the lights on. Seems like the brights caused the fogs to go out too??

Thanks ahead for any info or guidance

I have not, as of yet, made the fuse box wiring change. I haven't needed the fan yet. I'll dig through my notes.

[darrin]

Fleetwood and Famoroso -- the foglight circuit is triggered by a grey wire. If the fog lights only worked with the low beams on, the grey wire will be on the bottom of the low beam fuse. Move the grey wire to a circuit that's powered up when the ignition is turned on and you should be all set.

[Cory M]

Originally Posted by darrin

Fleetwood and Famoroso -- the foglight circuit is triggered by a grey wire. If the fog lights only worked with the low beams on, the grey wire will be on the bottom of the low beam fuse. Move the grey wire to a circuit that's powered up when the ignition is turned on and you should be all set.

That's what I said 2 years ago

https://forums.pelicanparts.com/porsche-911-technical-forum/1084369-fog-light-wiring-q.html#post11199339

[MBAtarga]

The existing dash switch location for the Cab top is another means of a manual control for the fan.

How many of sc owners keep the original trombone cooler?

[Fleetwood]

Perfect timing everyone. Just preparing to do the cooler fan wiring and I see the small gray wire atop the #5 fuse. Will confirm this is the trigger wire for the fog light circuit and test it on the new cooler fan. Thanks Darrin and Cory M for the info and related posts. I'll report back after some testing. Pelican really does rock

[Fleetwood]

Small gray wire atop #5 Fuse is the trigger and a butt connection and short length of 14 gauge to the top of #19 Fuse (headlight washer-not installed) and cooler fan control by the fog light switch when key in the on position. Exactly what I was hoping for. Thanks again to the responders

[7783911]

I ran a separate circuit and used a small switch on the dash to activate the fan versus a temp trigger

[spedrcr]

famoroso, where did you source the Kostal connector?

[famoroso]

Originally Posted by spedrcr

famoroso, where did you source the Kostal connector?

eBay



I was at the Hill Country Rallye for a couple days last week, running a 600+ mile mix of twisties, fast sweepers and faster straights reasonably hard with the oil cooler fan running. As the name suggests, the terrain features a large amount of elevation change (replete with a large amount of uphill WOT acceleration). This is what I saw most of Saturday...






Elsewhere on Pelican, a related thread:
At what MPH does 3.2 oil cooler fan become redundant?

[spedrcr]

Thank you Frank.

[Tom_in_NH]

The only part of that circuit that is fused is the switched coil current to the relay. The battery-to-fan current is direct and not fused (not recommended).

Originally Posted by 7783911

I ran a separate circuit and used a small switch on the dash to activate the fan versus a temp trigger

[spedrcr]

I discovered on my US 1987 targa the fog light relay trigger wire is gray and comes in the bottom of the license plate light fuse, second fuse closest to the front of the car.

[Classic 911]

Good thread


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