924Board.org

[Dynamite76]

Hi, Sorry if this is beat to death, but I want to put in a manual switch to turn on my 2 cooling fans while at the track. What I am hoping to do rather than running a wire from the temp relay into the cabin, it to find and use (if they exist) the wires that control the on/off for the fans that are already inside the cabin. I am thinking that they are running to the AC control switch, and that I can just splice into them with an on/off switch. Is this possible?

Thanks
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88 924S

[924guy]

if your wanting to keep the original functioning of the fans, but add a "manual overide" itll be a bit more complicated than just splicing in a switch.
what I would do, is run a new power line, through a relay to a switch in the cabin. on the fan side, id cut both fan power wires, soldier in zenier diodes (prevents power from traveling the wrong way) on each line, then After the diodes, create a "Y" from the new switched wire, each end also having a diode, and butt splice all that together at each fan wire. Or you could probably go in at the fan temp sensor wires, with the same zenier diode protected circuit.

the diodes are a must, if you energize the existing circuit, and the fan temp bridges , then youve got power coming from two sources at the same time, and things will get all hot and melty fast, at the very least..
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Eric
78 924
82 931 SE "smokey"
99' VehiCross
Y2K Honda Insight
http://www.cardomain.com/id/924Guy
Performance by Pasha

[924RACR]

My god that sounds horribly complicated.

I just have a second ground, in parallel to the rad switch, that provides an alternate ground path. One wire to run, real easy. I'm pretty sure the S is the same, pretty much.
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Vaughan Scott
Webmeister
'79 924 #77 SCCA H Prod racecar
'82 931 Plat. Silver
#25 Hidari Firefly P2 sports prototype

[Dynamite76]

I guess the quick "fix" for the moment is to disconnect the wires leading to the temp relay and run more wires (what I am trying to avoid) to a manual switch in the cabin. I know that the wires are run into the cabin in the main wire harness, just don't know which ones. I'll look into using diods in conjuction with leaving the temp switch connected once I figure which wires I can jump that already exist in the cabin. For now, I just have to remember to turn the switch on when things start to heat up.

Thanks
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88 924S

[924RACR]

Doesn't make sense. If you short out the temp switch in the rad, do your fans work? If so, all you need to do is put a manual switch in parallel to the temp switch.

If not, you should fix your stock wiring.

Do you understand how the stock fan wiring works?? Power goes to the relay, then to the fans, then grounds through the switch. The rad fan temp switch only switches the ground side.

ALL YOU HAVE TO DO IS PROVIDE AN ALTERNATE GROUND PATH.

NO relays or other fancy wiring are needed.

Review the wiring diagram.
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Vaughan Scott
Webmeister
'79 924 #77 SCCA H Prod racecar
'82 931 Plat. Silver
#25 Hidari Firefly P2 sports prototype

[Dynamite76]

Ah, but my temp swith is positively charged, not ground. Ask me how I know.

Yes, when I jumper the switch it is working fine, it is just that the temp switch (a new one too) doesn't cut on until the temp is almost 200 F. Too high in my opinion. Someone told me I should be able to find one that will cut on much lower as an aftermarket part, however, the manual switch is preferable to me anyway.

What I want is to find one of the existing wires in the cabin, jump the wires at the switch (by pass), and splice into the existing in cabin wire with the switch. I am not keen on having to run a positive wire back into the cabin if I don't have to.
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88 924S

[924RACR]

That's odd... well anyway, yes, you have (sounds like) the 95C switch; they also come in 85 and 75C... but I agree, it's appropriate to have a manual switch on a racecar.

It should be a pretty straightforward matter to reverse the wiring of the fans, make them ground through the rad switch, then run the alternate ground, still no relays needed...
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Vaughan Scott
Webmeister
'79 924 #77 SCCA H Prod racecar
'82 931 Plat. Silver
#25 Hidari Firefly P2 sports prototype

[Smoothie]

[Dynamite76]

Thanks for all of your help. My first prority was keeping it simple, second was avoiding running a positivly charge wire if I didn't have to.

Anyway, I just finished running the manual fan control. I used 12 gauge wire and attached 2 blade connectors to each end which fit snuggly in the thermo switch wires and secured with tape and zip ties. Loomed all of it and secured it well. I located the toggle switch in place of the sun roof switch.

Now all I have to do is think enough to turn the switch on when things get hot. Not a problem, although I am more likely to forget to turn it off and drain the battery since the main fan runs at slow speed when the ignition is off.

Anyway, new radiator (not even needed), system flush, addition of Water Wetter, and the manual fan control; the car should be able to handle the expected 95+ F degree weekend at VIR. I bought 4 white long sleeve shirts (no short sleeves allowed), and 4 of those freezer ice packs to keep the driver cool.

Car is washed, oil is changed, just need to adjust the headlights for the late Friday night drive to the track, check the torque on the lugs, air pressure and remember to bring my noodle bucket. Oh yeah, and put the belly pan back on.

Paul
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88 924S

[Smoothie]

[Dynamite76]

[Smoothie]

Well since you've already wired it up - you could leave it and have the same functionality as I just described if the rad temp switch were simply left in circuit. In other words** everything left as it was from the factory, then you'd have one of your added wires tapped-in or piggy-backed to the br/wt wire at one side of the rad temp switch and your other wire from the other side of your switch to the (br) wire on the other side of the rad temp switch (leaving the rad temp switch still connected to its' br/wt and br wires as from the factory - your wires and switch are just added without disconnecting anything)..


**- in still other words, exactly as 924racr suggested- "all you need to do is put a manual switch in parallel to the temp switch".

-But obviously if you need to keep the wiring in-cabin, tap into the br/bl or br/re wire as described in my last post...same result, different location.
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"..it's made in Germany. You know the Germans always make good stuff."


'82 924T, US version, dark green metallic, 5 speed Audi 016G gearbox

[924RACR]