shiners780

X-posted from the 924/931/944/951/968 Forum.

Just in case someone here has electrical experience but doesn't venture into the generic 944 forum:

https://rennlist.com/forums/showthre...ferrerid=31425

Thanks.

Bri Bro

I was going to do this during the winter. I was going to use the fan relay to run the fans, just fool the input to think it needs to run on high speed. I was going to connect one side of a push button switch to the 105C output from the radiator temp sensor, N34 on the central electric fuse box. The other terminal of the push button switch would be connected to ground. Push the switch in, both relays for the fans are turned on and the fans will run.

You could run 12VDC but they draw a lot of current so you should use a relay to avoid burning up the switch. Since the car has a fan relay, why not use it.

toddk911

I used a jumper on the AC relay plug and this way both fans ran all the time the engine was running with out the need for a switch.

Although, I could not get the AC to work like this. But I assume that is not a concern for you.

evil 944t

maybe this will help

toddk911

I've never tracked my car, but have certainly driven it very hard in the summer here in FL with temps close to 100 in the daytime, 18psi, stop and go traffic and getting on the boost hard in traffic etc. and never had a temp problem. Sometimes will get the the middle of temp. and then usually settles right back down.

I have stock cooling system except for low temp fan switch. And I no longer have the fans jumpered.

Bri Bro

This would be used only at the track. My car never goes above the second mark on the street. On the track in a 90+ degree day is a different story.

Dave, the switch can connect to the existing Fan relay, no need to add another relay and diode suppressor. Also, there are two sensors in the radiators thermo switch. One is at 92C (low speed fan) and the other is at 105C (high speed fan).

Todd, what pins did you jumper on the AC relay? I want to take a look at that solution.

evil 944t

Yes, your right. I was thinking that he is doing away with the factory wiring to lighten the car and then just hard wire it to work. Youu can also skip the relay if you run a 30amp switch.

shiners780

There's been good discussion at the link in my first post above.

I think (still awaiting confirmation) a simplistic solution has been found that retains the use of the stock coolant temperature switch as well as allowing for a manually controlled switch.

Bri Bro

I think that is what I said would work. What needs to be confirmed?
BTW: The link is bad.

shiners780

The link in my first post is good, for some reason it didn't work in my second post even though it's the same, I removed it.

They are suggesting the same thing you suggested. What I was waiting on confirmation for was the exact wiring necessary to make it work. They are telling me I need to run a 12 V power source to the switch, which you made no mention of. I was also seeking confirmation that no in-line fuse will be necessary.

I am a complete electrical noobie, so I want to confirm what needs to be done before I go getting myself into trouble (again) with the wiring. I'd rather do it right the first time, and things that are obvious to those familiar with wiring are not necessarily obvious to me.

Bri Bro

Don't see why you would need power for the switch, just ground. I will do a quick check on the car when I get home, see no reason it wouldn't work.

shiners780

I am looking at the wiring diagrams, and I think you're correct, no power should be needed for the switch. The manual toggle switch would basically act exactly the same way the stock coolant temp switch works, which is simply connecting the red/white (or brown/yellow depending on which fan speed) to ground, thus completing the circuit. The power for the fans appears to route through the stock fan relay directly to the fans. At least that's the way I read it. So all I need are two toggle switches with two connectors on the back and I'm in business.

If you could verify that once you get home, that would be wonderful! Thanks!

I guess the last thing I need to figure out is how many amps the switches should be rated for?

Bri Bro

Works great, just need ground. Here is how I checked it. I pulled the fan relay (big sucker) and I put a small wire in the TS (fan slow) and the FS (fan fast) terminal in the fuse box. Put the relay back in, turned on the ignition (didn't start it) and grounded one lead at a time.

Ignition On.
When FS was grounded, the fans were on high, with TS grounded, the fans were on low.

Ignition off.
Only TS grounded would run the fans (low speed).

This is what I expected to see. With a hot car, the fans will continue to run on low with the ignition turned off until the temp is below 93C.

So, all I need to do is connect a wire to the FS terminal and run it to a SPST push button with on terminal of the switch connected to this wire and the other to ground. When I push the button in, the fans will come on (fast speed) all the time the ignition is turned on. Turn the ignition or the push button off, the fan stop...perfect.

shiners780

Cool. Any idea what amp rating the manual switches have to be?

Bri Bro

A one amp Push button would be more then large enough. Grounding the FS pin turns on two of the Fan relays each drawing less then 0.1 amp. This means you can a run small wire from the FS pin to ONE push button switch. The wire should be around 24 gauge or less. As gauge number go down, the wire gets larger. The push button should be the on/off type, not a momentary. Not sure why you would ever want to run the fans continuously on low speed, I for one just want the ability to kick on the high speed fans to cool down the system when the engine is under extreme load.

I am looking at this push button from DigiKey. It comes with a yellow, red, blue or green LED illumination. Just need to connect a 1K ohm resistor to the LED + connection and ground to the LED- connection. I will hook up the LED to my dash light circuit. DigiKey number goes for 67-1944 to 67-1947 for the different colors. At least I know what I am going to do, hope this helps.

BTW : DigiKey does charge $5 for orders under $25.


http://rocky.digikey.com/WebLib/Lume...11A125S01R.jpg.

http://www.digikey.com/scripts/DkSea...253905&Site=US
http://www.lumex.com/images/pdf/CLS-PC11A125S01R.pdf