firejackal

DIY Electric Fan Installation for the Cooling System

Preface
This will be my second DIY.
There are plenty of instructions covering this topic, but I will be showing what I did to archive this, and why.

Four years ago when I bought my '96 S14 the prior owner had wired both the headlight positive and electric fan positive together to a switch on the middle console. It had no clutch fan, just was using the stock AC fan.
During the first year of owning the car I reverted the headlights back to stock wiring, then re-did the wiring for the fan switch.
Instead of the positive running to the switch I ran the positive to a relay which I taped into the AC fan power (12v with ignition acc/on/start), then ran the ground to the switch.
The next two years there was times I kept overheating the car from forgetting to turn on the switch.
Then last year I decided no more, I bought a neck fitting for the radiator hose and a water temperature sensor. And got it working properly. This DIY will be how I did it.
Some people prefer a controller, I prefer to get things done cheap, easily, and efficient.

Parts/Tools

• KA24DE: 36MM Water Temperature Sensor Adapter (ebay $5-$20) uses a 1/8" threaded hole for the sensor, this can be a difficult switch/sensor to find.
• 1/8" Thermostat Switch (ebay $25-$30) choose one with two terminals since our radiator neck (the adapter) isn't grounded, also I selected the 180'F version. I believe this is less then the stock thermostat temperature, so it will come on as soon as the thermostat opens.
• Wiring, I prefer 14-16 gauge when working on this higher amperage components.
• Shielded spade terminals (at least buy two female terminals used to connect to the sensor) or you can solder the wires, I prefer a way to easily change the sensor if it stops working.
• Hose cutters, I used heavy duty wire snippers. You can also use a hacksaw.
• New coolant (or strain your existing coolant if re-using.)

Warnings

• The thermostat switch (sensor) is fragile, when tightening it, don't torque it, it will snap in half.

Images
The AC fan I re-used.

The radiator hose neck adapter (36mm) with the thermostat switch, if you noticed I opted to cut my radiator hose and then connect the hose neck. Make sure you don't have any leaks here.

The relay with my messy wiring in the engine fuse box.


Wiring

• The relay coil is powered by our "signal to turn on" for this you want to use your Ignition Switch On. An easy source for this is the BLUE/ORANGE wire off of either the Cooling Fan Relay 1 or 2. If you want to keep your cooling fan, just splice/solder onto either wire.
• The relay coil is grounded by our method to turn on the fan, for this I kept my center console switch (for AC purposes), and the thermostat switch.
• On the thermostat switch, make sure your female spade terminals is tight, if not, squeeze the metal plugs together, you don't want these coming off when out and about (I had this happen.)
• On the relay switched side, this is your power to whatever fan you decided to use. One side of the relay switch terminal you want your power source here, you should use a "hot" source. The other side will go to the fan(s). You can either re-use the factory AC fan, or wire in one or two slim fans. Either works, I have used both.
• On the factory AC fan you'll be using the "high" side which is pin 1 (white/red) the other wire is pin 2 (brown/white) and used for the "low" size. The grounds are both black wires.

Steps

1. Drain the coolant out of the radiator.
2. Cut your lower coolant hose (from thermostat housing) at where you want to put in the sensor hose neck. I choose close to the thermostat housing.
3. Attach the sensor hose neck, along with the switch/sensor. Clamp this down good, the hose neck is aluminum and shouldn't break.
4. Refill your coolant, pre-check for leaks around the fitting.
5. Follow my wiring diagram to wire up the thermostat switch, fan, relay, and emergency switch.
   I placed the relay and fuse inside the fuse box (along with finding power in there) and then routed my center console switch wire through the rubber grommet behind the driver fender. My center console was missing the ashtray, so I made a panel at that spot.
6. Test it out! First check the physical center console switch, it should work. Then let the car warm up, keep checking for leaks, the fan should turn itself on when your thermostat opens.

That's it, it's a straight forward procedure.
After I did this, I ended up doing the same thing to my MK3 Supra (since my 2JZ was missing the clutch fan as well) but using two slim fans.

Any suggestions, advice, edits, etc, feel free to reply on here or message me. If some reason the images go down, contact me and I'll try to get them back up. Once this is solid I can try to get it to a PDF.