shiners780

My plan is to hard wire each radiator cooling fan to a separate toggle switch on the dash (one switch per fan).

From what I understand, I would run the black/red wire from a fan motor directly to the switch, then run a wire from the switch to a power source on the fuse box.

My questions are:

1. What power source at the fuse box to use? Should I use a fused location from an accessory that I have removed, such as the fog lights. Or should I use a direct power source and install an inline fuse?

2. In order to purchase the toggle switches, I need to know what amp rating the radiator fan motor is but I don't see it listed on the wiring diagram. What amp rating is the fan motor?

3. Since the fan motor is already grounded, do I also need to ground the toggle switch? (The switches have a blade connector for a ground.)

4. I assume doing this would allow me to remove the fan relay?

Is there anything else I need to know or do?

Thanks in advance.

theedge

Why do you want to hardwire them? Just curious. Be pretty easy to wire it up to use one or two fuses on the fuseboard. Youre also aware that without some extra wiring and multiple switches you wont have the high/low.

Going to use the stock wiring out to the fans or replacing it?

Campeck

prolly for his track car. the more cool switches the faster you go.

xsboost90

are you going to leave your fans on the entire time you are driving? That will make your engine temps way too low and the car may never get up to temp- however you wire it, i would make it go through the temp switches still so they kick themselves on and off like they are engineered to.

968rz

You might want to think about wiring in a relay to that circit, the fans are rather high amp and could over heat or melt the switch if you go direct. (just a thought)

schwank

Jim I was staring at mine yesterday pondering the same thing. At the very least I need to do one side, as I've removed the AC.

From the amp rating of the fuse (35 IIRC) it needs a bit of current. I've read of using the diagnostic port for power, and I also have random drops from other stuff like cruise control that has been removed, but I don't think any have that much current.

I am currently leaning towards building my own using a direct wire with inline fuses. I also need to run cutoff switch wiring so I'm trying to plan it all at once. For now as it is a street car I think I'm going to let the relay trip the primary fan, but getting rid of that would be one nice side effect.

Dmitry S.

You can bypass the relay, it's a low amp circuit that way. When my fan relay failed, I temp. rigged up a switch.

Waterguy

Since you need to run a relay to handle the current anyway, why don't you use the stock fan relay and use toggle switches to replace the coolant temperature switch? You need either two toggle switches or one two-position switch. I don't know what current rating you would need, but it is very low since the coolant temperature switch is wired using 0.5 sq. mm wire - slightly finer than 20 gauge wire.

Low speed fan: run a 20 gauge wire from either pin N23 on the central electric or pin 2 on the coolant temperature switch connector (brown/yellow stripe wire) to a toggle switch, then to a ground point.

High speed fan: run a 20 gauge wire from either pin N34 on the central electric or pin 1 on the coolant temperature switch connector (red/white stripe wire) to the second toggle switch, then to a ground point.

To use this set-up, you need to keep the stock fan relay G10, the two large 0.9 ohm ballast resistors and their heat sink, and the stock fan wiring harness.

I don't think you do. Iirc, the fans are turned on at high speed by EITHER the AC switch or by the high temperature side of the coolant temperature switch. I know my fans go on high at the track without the AC turned on.

sillbeer

the thermostat controls the engine temperature, not the fans

xsboost90

i agree- if you thermostat is too low a temp your engine will run cold-so why are there fans? There is a thermostat in the radiator that controls when the fans kick on- usually at low speeds granted- but the system works well- why would you eliminate all of that- to save five ounces of weight? I guess if you are eliminating the entire harness and going w/ a painless system or something it would make sense- guess im not enough of a race car guy yet. Just seems to me that it would be easier to have a system that maintains its own temp as opposed to you sitting there watching the gauge and flipping switches up and down to compensate...

PeteL

Are the fans working at all? If so, why change? If the car is overheating, you have other problems.
If the fan circuit is FUBAR, I can provide directions to replace the fan circuit which will give you fans that operate similar to stock, ie: they will still use the temp switch in the rad to activate the fans as necessary.

I used to have the fans wired to a switch, and all that did for me is enable me to run the battery down a few times when I forgot to turn them off. Much happier with my homemade fan circuit. (the relay is now useless as it is completely removed from the equation, although it is still in the relay board)

M758

I have the fan direct wired on my 944 race car.


I have two sets of wires runing direct from my batter (through the kill switch) in to 30 amp fuses direct to each fan. I have switch for each fan so I can chose no fans, 1 fan or both depending on water temps. Switches are 30 amp switches. I think the nominal draw is liek 15 amps, but it will spike to 25 amps on start. Interestingly the current draw is so much that I need turn off the fans to start the car. It won't start if I run both fans.

Oddjob

Can the bank of resistors (two big green ones on the firewall by the battery) be eliminated/bypassed?

spazegun2213

Thats how i did one of mine. I'll do the other like that this winter. I first had 20 amp fuses that i would blow all the time, but the 25's i have in it now seem to be working just fine.

It too me a hour to get all the wiring in, hooked up to everything and works like a charm.

shiners780

This is a very common modification on track-only cars, and it's merits have been discussed at some length on the Racing/DE Forum.

I did not realize that I could install manual switches while at the same time utilizing the stock coolant temperature switch. That is perfect!

Waterguy's set-up seems like the most logical and useful approach.

Just so I completely understand: Regarding the low speed fan wiring, if I run the brown/yellow wire from pin 2 on the coolant temp switch to a manually operated toggle switch, do I cut the wire as it leads into pin N23 at central electric? Or do I splice into the wire so that it is still completely connected between the coolant temp switch and central electric but with a new wire jumpered in and run to the manual switch? Remember, wiring isn't my forte. And just to further clarify, the manually operated toggle switch would then have only two wires attached to it: one would be the brown/yellow, the other would be a ground, correct? And no need for an in-line fuse since I would still be utilizing the stock fan relay?

This set-up would then allow the coolant temperature switch to automatically turn the fans on as originally intended, and also give me the option to manually turn the fans on, correct?