Planning And Executing Your First Cooling Fan Wiring Job

If you don’t have a lot of experience with automotive wiring, any task task involving this “spaghetti” of electrical conduit can seem intimidating. But when discussing wiring, the cooling system is not normally uttered in the same sentence. However, the cooling system of many cars do require wires, and it all needs to be done correctly. We’re here to help our inexperienced readers understand how to attack the basic wiring of fans as part of a cooling system wiring project.

Fan wiring does not have to be scary; you just need to arm yourself with a little bit of knowledge and the right tools. Thankfully, fans for a cooling system can easily be wired up, but there are a few things you need to keep in mind during the project. We talked with our friends at SPAL to get some basic tips lined up to help you start a cooling system wiring project.

Wiring a cooling fan may seem simple, but there are a lot of ways to mess-up this task if you’re not careful.

The Basics Of What To Do And Not To Do

Your first step should be to come up with a plan that covers where wires will be run before you start snipping and splicing anything. You’ll also want to lay out what materials are required for the project. Another thing you need to do is to make sure you have the right tools. We’ll cover what you’ll need later in the article.

It’s a good practice to keep all your wiring away from heat sources like the exhaust as well as any moving parts under the hood of your vehicle. Make sure you’re routing the wires so they can be properly secured to the vehicle. You don’t want loose wires running amok. It’s important to secure the wires so they don’t get in the way when you’re working on the vehicle or become damaged. If the wires aren’t secured and laid out neatly, it can make troubleshooting difficult if there’s ever an issue.

The gauge of the wire that you use in your cooling system wiring harness is very important. SPAL’s Greg Goeders explains why you need to make sure you’ve got the right size wiring running to your cooling fan.

“You have to make sure the wires used to power the fan are ample sized for the electrical load the fan is expecting to see. Wires, just like fuses, have a time rating during each loading condition. If the amperage is high, the time the wire can handle the load will be very short. If the amperage is properly aligned to the wire size, the wire can handle the load indefinitely. Making sure the wire can handle both the startup load and the operating load is critical to long-term electric fan success.”

Don’t skimp on the gauge of the wiring you use for the cooling fan.

Most fans, like the ones SPAL offers, will indicate what size wire is required for that fan. Don’t take this merely as a suggestion, take it as the final word on the subject and adhere to the recommendation.

“It doesn’t hurt to go bigger on wire from a technical aspect. You don’t want to try and visually match the wire from the fan to some random wire you have in the shop. Instead, use the correct gauge wire required according to the amperage value given when purchasing the fan,” Geoders states.

Building protections into your cooling system wiring is a good idea. A fuse of some kind should be included in the wiring. This will protect your vehicle’s electrical system if there’s a malfunction. If you’re going to be using brushed fans, a relay will be required. The relay is there to deal with the heavy initial current draw of the brushed fan when it starts. Brushless fans don’t have a high current draw since they use a “soft start”, so the relay isn’t needed.

A relay is required for any brushed cooling fan. It will help the electrical system deal with the load generated by the fan when it first starts.

There are a lot of ways to come up with the wiring for your cooling system, and that makes it easy to make the task more difficult than it needs to be. This is one area that can get new-to-wiring people in trouble.

“The biggest mistake people make when wiring a fan up into their car is making it overly complex. In the most basic sense, all the fan needs to run is power and ground. Give the fan 12 or 24 volts, depending on what fan is purchased and it runs rain or shine. It’s great to customize the engine cooling package to get two minutes of extra cooling when the vehicle shuts down or kicks on perfectly in sync when you turn on the A/C, however, this is not required,” Geoders says.

Tools And Materials

You don’t want to start wiring your cooling fan into your vehicle’s wiring system without the right tools and materials. If you’ve never wired anything on your vehicle before, this is a good opportunity to invest in some items you’ll be able to use on other wiring projects. You don’t want to be excessively cheap when it comes to the materials and tools you purchase.

Wire is important, but you also need the right connectors as well. This is another area where you don’t want to cut any corners.

Based on the scope of your project, you’ll want to make sure you have plenty of high-quality wire that’s intended for automotive use. The wire should be made of copper and have good insulation surrounding it. You want copper wire because it’s more conductive and won’t corrode like aluminum wire. The quality of the insulation is important because it’s what protects the wire from contact with metal. You don’t want to be in a situation where you’re chasing shorts in your wiring because it’s grounding to the vehicle due to shoddy insulation around the wiring.

Connectors will be required to link everything together in your cooling fan wiring harness. You can use a soldering iron to hardwire everything, but that can be tedious and difficult, depending on how you run the wires. The easier and more common approach will be to use butt, spade, and ring connectors in the appropriate locations. These connectors are easy to find at your local auto parts store, and don’t require any special tools to use. You’ll also want some shrink-tubing to protect your connections.

Don’t forget your fuses, they can prevent electrical fires.

Your overload protection and other possible miscellaneous materials are the final things you’ll need to add to your wiring shopping list. You’ll want to be sure you have the right fuse and fuse holder for your application. Most electric fans are going to be rated in the 19 amp range, so you’ll need a 25-amp fuse at least to deal with the load. As we discussed earlier, if you’re going to use a brushed fan a relay will also need to be implemented into the wiring.

Invest in the right tools for the job. It will make the wiring project easier and you can use them for other jobs in the future.

The right tools make wiring projects much easier. You’ll need something to strip the insulation off the wires. There are lots of options out there, from your basic set of wire stripping pliers, all the way to specialized wire stripping tools. The next thing you’ll need is a tool to crimp your connectors. You can use the basic wire stripping pliers for this, or you can invest in a wire crimping tool. If you’re being fancy, the soldering iron is also an option as well to connect wires. Finally, you should also have a volt/ohm meter and test light on hand to check for any issues.

Wiring up a cooling fan can be done with little to no wiring experience. You just need to make sure you understand the scope of the project, and have a plan, the right materials, and the correct tools.

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Brian Wagner

Spending his childhood at different race tracks around Ohio with his family’s 1967 Nova, Brian developed a true love for drag racing. Brian enjoys anything loud, fast, and fun.
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