Manual Cooling Fan Switches

[rick3000]

It seems like people are getting a bit confused, perhaps I can help clarify. To manually trigger the fans, all you have to do is ground Pin 85 on the existing fan relays. I used the ground from the phone connector, you literally run a wire from the ground to the relay. You then interrupt this wire with a switch, so you can turn it on and off. With the switch off, the fans work as they always have, with the switch on Pin 85 on the fan relay is grounded and the fan are manually turned on.

You can do this with a simple switch (pictured above), or the OEM switch and a latching relay. The OEM switches do not stay on or off they send a momentary signal when pushed, so you need a relay that stays on or off when it gets the momentary signal from the OEM switch. I chose to only connect the high speed fans, because the low speed fans come on with the AC, so I didn't see the point. And with the OEM switch, you would need two switches one for the high fans and one for the low fans. If you want both the high and low fans with one switch, you use a 3 position switch, the middle/off position is the ground, then the high and low are the other two positions.

You can also wire the engine compartment fan the same way, by grounding Pin 85, but I haven't done it since the relay is in the rear trunk so you need to route the wire a long way.

I have a write-up on the radiator fan mod using OEM switches in the batwing, and how to get them backlight. It's here: DIY: Manual Radiator Fan Switch w/ an OEM Switch

[piper6909]

Originally Posted by Starter986

Hi Pipe,

Quads.

I just want a manual on/off switch for the high speed fans. I'm no electrician... but can walk around it a bit.

I know one 3 position rocker switch's three prongs will be grounded.

One prong of the rocker switch will be connected by wire to the #85 prongs on the two high speed fan relays.

It's the wire connected to the third rocker switch prong that I'm stuck on... wondering where does that wire go. To what does it connect so that when I hit the switch... the fans come on. Does it go to another prong on the high-speed relays? Quad was unclear about that third wire.

Thanks, Pal.

Quad's set-up is a little more complicated than JgKram's. This is my understanding of how the existing setup works:

Pin 86 on the relays have constant 12volts. Pin 85 goes to the ECU which grounds it at the appropriate temp, which completes the coil circuit and trips the relay.


Both methos use a Single Pole, Double Throw (3-prong) switch.

Using Quadcammer's method, you'd cut the pin 85 wire (I believe Quad said it was yellow) and, splicing in a jumper wire, run the RELAY side of the wire to the MIDDLE prong of the 3-way switch. Run the ECU side of the wire to the BOTTOM prong, and run the TOP prong to ground. This way, with the switch in the UP position, it completes the circuit with the ECU, and the ECU decides when the fan comes on. In the middle position NOTHING is connected and the fans NEVER come on. (I wouldn't advise that), and in the bottom position the circuit is completed through the ground wire you ran and the fan runs all the time. You can splice the yellow wires from each relay, (left and right side) together and run both to one switch. This would do either high or low speeds. I guess the consensus is to just do the high speed, and don't bother with the low.

Using Jgkram's method, you'd get some fuse taps and connect them to the to the 85 pin of each relay. This keeps existing circuit to the ECU intact. Using jumper wires, splice together the two high speeds and the two low speeds. Run the low speed to the top pin of the switch, the high speed to the bottom pin, and ground to the middle pin. In the up position, the high speed is grounded through the switch, in the bottom position the low speed is grounded and in the middle position the ECU will have control.

You can also use a single pole, single throw (2-prong) switch and run only the high-speed circuits only. Run the jumper wires to one prong and ground the other prong. this way, in the OFF position the ECU would have control and in the ON position you will override the ECU and turn on the fans.

Either setup works fine. It's up to you which one you'd rather use.

[Starter986]

Rick... Pipe... thank you for the very clarity I needed. I was overthinking it. I'm no electrical wizard.

Quad... thank you for your help!!

Cheers!

[Jgkram]

Piper was spot on in his assessment. The hardest part of this modification was crawling in the footwell to hook things up to the relay panel. I must admit that I really wanted to make my modification similar to Rick's as his is more elegant but just wasn't up to it at the time and I took the easy way out. However, I have been very pleased with this modification and have used it often during stop and go traffic in the summer months. I haven't used the engine cooling fan nearly as much so that one could be left off but while your doing the mod, why not.

[Starter986]

I ran a wire from pin 85 to ground... and the high-speed fan kicked on (only tested one side).

Just purchased standard round rocker switch... but am thinking that even with the 5 prongs on the back of part #986.613.134.00 (Porsche Boxster Lock Switch Black) I could connect to two of the prongs and achieve the same result, correct? Wire to ground... wire to pin #85... abandon the other three prongs.

Yes? No?

That Porsche Boxster Lock Switch Black would look better than the rocker switch.

Thanks!

[piper6909]

Originally Posted by Starter986

I ran a wire from pin 85 to ground... and the high-speed fan kicked on (only tested one side).

Just purchased standard round rocker switch... but am thinking that even with the 5 prongs on the back of part #986.613.134.00 (Porsche Boxster Lock Switch Black) I could connect to two of the prongs and achieve the same result, correct? Wire to ground... wire to pin #85... abandon the other three prongs.

Yes? No?

That Porsche Boxster Lock Switch Black would look better than the rocker switch.

Thanks!

Those switches won't work because they're momentary switches. I.e. they don't stay closed when you pull your finger off them. An additional relay needs to be added to get those to work.

[Starter986]

Originally Posted by piper6909

Those switches won't work because they're momentary switches. I.e. they don't stay closed when you pull your finger off them. An additional relay needs to be added to get those to work.

Thanks, Pipe.

[Jgkram]

If you want to use those switches then follow Rick's instructions for adding his relay. I think I still have some of the same switches I used and if I can find them you are more than welcome to them. I used a progressive drill bit to drill the holes in the batwing.

[Starter986]

Thanks for the offer Jgkram. I appreciate it. I'll pass for now... but will revisit that addition when I get tired of the non-stock rocker switch. That said...

I'm entertaining adding a manual switch to the engine compartment fan. Entertaining meaning is already I've cut and prepared the wires. All I need is to pick up another, matching, switch.... with the exception of running the one, singular, wire from relay to switch.

I'm assuming I'm, via wire and switch, jumping pin #85 of the #8 relay in the frunk... the engine comnpartment fan blower relay. If affirmative... it's the same setup as the radiator fan switch with the exception of one relay vs. two. Now...

That wire running from the #8 relay in the trunk up to behind the center dash console. If anyone has the/ANY method, tips, or tricks to run that wire in the most expeditious manner possible... greatly I would appreciate them.

Jgkram... I like the buttons in the batwing. I removed my wing... examined it... saw the opportunity for some Dremling... and decided against it for the time being. The circuit is so simple that I could remove it in 30 seconds... when I go the wing route. However, I know I will be "entertaining" some cutting in the near future.

I didn't want to mount the switch where it would look terrible out of place. I settled on snuggling it into the side of the cubby (for owner manual) under the steering column. When I asembled the wires and end connecters I heat shrinked everything so you see no silver prongs (even heat shrunk the unused prong). The two wires from the switch I then encased in the round accordian looking sheath hiding thr wires up to under the dash. Looks clean... and doesn't attract "ricer" attention. Until I'm prepared to cut into the batwing the other, engine compartment fan switch, I'll position at the other end of the cubby.

Thanks to everyone who pointed me in the right diorection on this most-easy mod.

Now... about running that wire fron the trunk... past the engine bay... into the cabin... and to behind the center dash console...

Thank you.

[piper6909]

Originally Posted by Starter986

Now... about running that wire fron the trunk... past the engine bay... into the cabin... and to behind the center dash console...

Thank you.

My car came with an aftermarket backup camera. IIRC, they ran the cable through the hole where the shifter cable goes through. If not that, there's a wiring harness there too. They both go under the center console and into the engine compartment.

[jaykay]

Originally Posted by rick3000

It seems like people are getting a bit confused, perhaps I can help clarify. To manually trigger the fans, all you have to do is ground Pin 85 on the existing fan relays. I used the ground from the phone connector, you literally run a wire from the ground to the relay. You then interrupt this wire with a switch, so you can turn it on and off. With the switch off, the fans work as they always have, with the switch on Pin 85 on the fan relay is grounded and the fan are manually turned on.

You can do this with a simple switch (pictured above), or the OEM switch and a latching relay. The OEM switches do not stay on or off they send a momentary signal when pushed, so you need a relay that stays on or off when it gets the momentary signal from the OEM switch. I chose to only connect the high speed fans, because the low speed fans come on with the AC, so I didn't see the point. And with the OEM switch, you would need two switches one for the high fans and one for the low fans. If you want both the high and low fans with one switch, you use a 3 position switch, the middle/off position is the ground, then the high and low are the other two positions.

You can also wire the engine compartment fan the same way, by grounding Pin 85, but I haven't done it since the relay is in the rear trunk so you need to route the wire a long way.

I have a write-up on the radiator fan mod using OEM switches in the batwing, and how to get them backlight. It's here: DIY: Manual Radiator Fan Switch w/ an OEM Switch

Yes this makes perfect sense and I am not sure why one would need more than one relay to ground three pin 85s for all three fans to come at once via a stock momentary contact switch. Three leads through s latching relay to ground. One switch in the empty spot up top controlling it all.

Not sure why one would want low fan speed as well as hi.....it's the same fan no?

I am curious about what the seat heater switch does. Can the two different positions trigger rad fan and engine compartment fan separately .....with two relays of course ( not sure how a step works)

[rick3000]

Yes, I never saw the point in hooking up the low speed fans since you can already toggle them on/off by running the AC, and yes it's the same fans, the high or low relays just run them at a different speed.

But you need to be careful with using different OEM switches, they are not all the same internally, so the wiring will be different than how I wrote it up. Most of the OEM switches fall into one of two "types" but there are also some other variations. If you want to use a different switch you need to look at the wiring diagrams in the Bentley manuals to see how the switch is wired internally. I don't think any of the switches with left and right buttons would work with night illumination. The defroster switch I used is basically one button, it doesn't matter if you push the left or right side.. If you don't care about illumination, all the switch has to do is take a 12V input, and send that 12V signal out when you push the switch to trigger the latching relay into the "set" or "reset" position, so you could probably hookup two latching relays with two different functions to one switch.

[Starter986]

Originally Posted by rick3000

Yes, I never saw the point in hooking up the low speed fans since you can already toggle them on/off by running the AC, and yes it's the same fans, the high or low relays just run them at a different speed.

But you need to be careful with using different OEM switches, they are not all the same internally, so the wiring will be different than how I wrote it up. Most of the OEM switches fall into one of two "types" but there are also some other variations. If you want to use a different switch you need to look at the wiring diagrams in the Bentley manuals to see how the switch is wired internally. I don't think any of the switches with left and right buttons would work with night illumination. The defroster switch I used is basically one button, it doesn't matter if you push the left or right side.. If you don't care about illumination, all the switch has to do is take a 12V input, and send that 12V signal out when you push the switch to trigger the latching relay into the "set" or "reset" position, so you could probably hookup two latching relays with two different functions to one switch.

That's why I went the simple route. One wire from Pin #85 on the relay to a switch... another wire from the switch to ground.

Dunzo.

If there is a reason why people are complicating the setup with relays... looking at wiring diagrams... why would anyone want to do such a simple, simple mod with overkill methods?

Tell me. Thanks!

[piper6909]

Originally Posted by Starter986

]

If there is a reason why people are complicating the setup with relays... looking at wiring diagrams... why would anyone want to do such a simple, simple mod with overkill methods?

Tell me. Thanks!

The only reason I can think of is if they want to use original Porsche switches (for appearance). Those switches are momentary switches so a latching relay will be required. If you use a normal style switch no additional relay is needed.

[Starter986]

Originally Posted by piper6909

The only reason I can think of is if they want to use original Porsche switches (for appearance). Those switches are momentary switches so a latching relay will be required. If you use a normal style switch no additional relay is needed.

Gotcha. Likely at some point that is the route I'll go. The $10 rocker switches aren't exactly meshing with the interior. However... I've got the setup nicely heat-shrinked... and kind of hidden nestled into that cubby under the steering wheel.

I believed my hookup to be somewhat complicated... and was wrong. I'll overcome the electrical fears and fashion up everything proper.

Then the paddle shifter mod.

Have a great weekend!