Short story: I followed this DIY on how hook directly to the Aux fan wiring with a 80C switch. Easy to do, simple and not a lot of electrical cabling. I was running a SPAL 16'' Puller as my primary cooling fan for a few months.
This worked like a charm- except under the ONE scenario: If the temp switch kicks on the fan at 80C and starts cooling, and I was ready to park or turn off the car and the fan was still on- the fan would obviously lose power. IF I had to turn the car back on for whatever reason (maybe to move the car after you parked it) and the temp was still over 80C- the startup of the ignition I would blow the stock 30A aux fan fuse every time. I found out that this can happen when switching from the +12v of the battery (ignition ON but engine OFF) to the new +14.3v you get from turning over the engine and obtaining the power bump from running from the Alternator. By the way- I never blew the in-line fuse I added from the +12v of the fan- only the 30A fuse in the fusebox.
Also- which is a great point on why I modified it- was that say you are getting ready to pull into your destination, you might be idling a bit to find parking etc etc and the car gets up to 80C. The fan kicks on and might still be running when you turn the car off. Which is fine. But if you need to turn the car back on again, the thermo switch on the thermostat- which goes to the DME- will tell the DME that the engine coolant is too hot and don't supply fuel. So you get this hesitation when trying to start up. I can't get a definite temperature of what the thermostat DME switch reads that tells the engine that it is too hot. I only found out what resistance it reads at certain temps. If you know- I would really be interested what this threshold is.
Anyway- my plan was to remove the fan from the Aux wiring fuses/relay and run power directly to a new relay that has constant +12v w/o the ignition on. First tried to wire up a new relay and fuse to the stock fusebox. Wasted my time since I couldn't find the correct female blade inserts for the fusebox. Decided to do a completely standalone setup.
Here is what I used and how I wired it in:
Hella 30A Relay and weather proof wiring harness $15
- Relays are pretty much all the same from what I found. Went with this one since I decided on mounting it stand-alone from everything else and tried to make the install clean. Sure you can use a standard Autozone 30A relay, but finding the wiring harnesses are hard to find locally and at the end it will probably be a pretty messy wiring job. Installed mine on the side of the fuel pump relay cover.
30A In-Line fuse holders $4/each
- Used this instead of using the Accessory fuse holder (some have used this stock fuse holder for other things) Put one from the +12v Constant coming out of this stock fuse holder to terminal 30 on the relay. Used the other one for the +12v for the fan.
Here is my drawing and relay layout.
Relay Wiring
Terminal 30: +12v (12GA wire) constant from stock accessory fusebox (with In-line 30A fuse)
Terminal 85: Ground (12GA wire)
Terminal 86: Trigger switch (14/16GA wire) I'm using my 80C thermo switch with a manual override switch that I used a extra fog light switch and mounted it next to the defrost/hazards (to turn on the fan under 80C if needed) You need to tap into a 7.5 fuse that has constant +12v so fuses 21, 22 and 23 are always on. I tapped fuse 21 (NOT 10 as pictured) since it is used for other switches on the car. Run a wire from here, to the thermo switch. Then a second wire back to Terminal 86.
Terminal 87: Fan +12v (12GA wire) used an in-line fuse here to protect the fan. Mounted it near the fusebox for easy access.
Terminal 87A: NOT USED (unless you need power to something that is ALWAYS on and OFF when the fan is ON)
Notes:
Make sure you invest in good butt connectors, crimp (or solder if you prefer) and electrical wrap. I hate glossy electrical tape, so I purchased some premium wire wrap.
Thats about it! It's not the most complex job, but it gets it done and doesn't rely on anything stock. Hopefully this will help out people who might see the same issues. There are a few threads around that I've read about their fans blowing fuses left and right. This should be the solution. Good luck!!
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