DIY Electrical Automotive Projects Even You Can Do

Updated on January 19, 2019
WheelScene profile image

Bud Scannavino is a Certified Master Automotive Technician. When it comes to modifying cars, Bud believes in excess.

You might not be fixing your power locks or windows, but there are automotive electrical projects you can do.
You might not be fixing your power locks or windows, but there are automotive electrical projects you can do.

DIY Electrical Automotive Projects

Every modification you make to your car does not have to be big, expensive and time consuming. Yes, it’s nice to have mods that make your car louder, faster or fiercer—or at least have mods that give that impression.

But it’s the small modifications that will make your vehicle more enjoyable as an everyday driver. From little creature comforts to gadgets that are always nice to have, the small extras make the biggest differences.

Small electrical projects on your car fit that category. They are well within the mechanical capabilities of anybody doing DIY car maintenance or modifications. But many people resist doing anything electrical in nature to their car. They shy away from electrical projects. But a little bit of experience will go a long way toward building confidence. Start small. So, let’s look at a few small electrical projects that you can undertake.

Change Your Spark Plugs

Changing your spark plugs is an easy car maintenance project anybody can do.
Changing your spark plugs is an easy car maintenance project anybody can do. | Source

Technically not a modification, replacing spark plugs is a routine maintenance chore. Not as frequently scheduled as with cars of days gone by, it is still important to know when and how to change your spark plugs. Having fresh, clean spark plugs is vital to performance, fuel economy and reduced emissions.

Clean Your Battery Terminals

The most common reason cars won’t start is also the easiest problem to prevent. Battery cable terminals work themselves loose over time and develop corrosion, and that impedes the flow of current. It’s normal. It’s also normal for that to create a problem and prevent your car from starting.

Always wear safety glasses when working with your battery. It produces explosive hydrogen gas, and those gasses can be ignited forcefully by only a tiny spark, like when you accidentally ground a wrench while loosening the positive battery cable.

For that reason, always remove the ground terminal first, and always install it last. Stack the deck in favor of your safety. And if you have to remove your battery don’t struggle to grip the heavy cube with your fingertips. Buy an inexpensive battery lifter. It is a rubber strap with metal teeth, and you can buy one at the parts store. It’s always nice to add a tool to your collection.

Replace Your Bad Light Bulbs

There are more light bulbs in your automobile than you think.
There are more light bulbs in your automobile than you think. | Source

Yes, just as light bulbs burn out in your house they also burn out on your car. And a typical car has a few dozen light bulbs, though it might not seem like they do.

Many are external, and a lot are in the interior. Many more are inside the dashboard, and some cars even have them inside the glove box, the engine compartment, in the doors and inside the trunk. That's a lot of spots.

It’s amazing vehicle light bulbs last as long as they do, considering the jostling we put our cars through. Plus, all those bulbs are exposed to humidity and moisture from the weather, the freezing cold of winter and the searing heat of summer.

Check them all. Get help checking the brake lights. When replacing any exterior light bulb always apply a thin film of dielectric grease to its metal base and to the contacts. That special grease will help to slow down the growth of corrosion. That’s the white and green stuff you might find growing on your old light bulbs when you remove them. Dielectric grease would have prevented that corrosion from forming. Buy it at the parts store. It comes in a small toothpaste-like tube. It’s also cheap.

Learn How Relays Work

The typical four-prong relay has two circuits: one light-duty control circuit and one heavy duty "load" or "work" circuit.
The typical four-prong relay has two circuits: one light-duty control circuit and one heavy duty "load" or "work" circuit. | Source

Relays scare people. I don’t know why. Maybe because they work by the invisible magic of electricity, have no visible moving parts (on the outside), and seem to be found all over the car. You will find heavy concentrations of relays under the dashboard and in the engine compartment. Some cars have them elsewhere, like in the trunk and under the rear seat, anywhere engineers can squeeze in a few more relays. They probably think the more, the better.

Since several of the following easy electrical projects involve working with relays, it’s worth getting acquainted with them.

Think of relays like this. If you can understand the mechanical principle of a lever, then you can grasp the electrical concept of a relay. With a lever, a small amount of force can do a great amount of work. Same with relays.

Suppose you wanted to install an accessory that draws a huge electrical current. If you ran the wires from the fuse box or battery straight to the accessory, you would need a big, heavy and ugly electrical switch inside the car to turn the accessory on. No good.

You don’t want industrial-grade switches inside your car. Instead, you could use a small, user-friendly switch inside the car that would activate a heavy-duty switch somewhere out of sight. Get the picture? That’s all a relay does, nothing more. Sorry to disappoint you on how simple they are.

So, go to your favorite parts store and buy a four-prong, 30 amp, 12-volt relay. Study the wiring diagram printed on its cover (you will need good eyes or glasses, because relays are small, about the size of a matchbox).

The typical four-prong relay has two circuits: one light-duty control circuit and one heavy duty "load" or "work" circuit. Its operation will become clear as you study it a little.

Install Louder Horns

We don’t usually think of horns as an accessory that we’d like to add to our car. That is, until someone starts veering into our lane on the freeway. At that moment we always wish we had those really loud air-powered horns that 18-wheeled trucks have. Nobody ignores the blast of those horns. And yes, they are powered by relays, as are the standard horns on your car.

Horns are rated by decibel output. The higher the decibel rating the louder they are. The box the horns come in will always state the decibel rating on the outside, typically in huge numbers, followed by a few exclamation points to suggest just how loud the horns are.

Horns are easy to attach anywhere you can fit them (outside the car, not inside). After you figure out the simple mounting brackets and where to locate your new, extra loud horn, use your relay and a standard automotive switch button to supply power. Now you can wake your neighbor up at night when you come home. You know the one, the guy who always mows his lawn at 7:00 am on Saturday morning. That guy.

One last word. When bolting the horns in place, face them down so they don’t collect moisture, rain and water from puddles that might get splashed up on them. When a horn does fill up with water it will sound just like a duck call. I’m sure that is not the effect you are going for, especially when somebody starts veering into your lane on the freeway.

Install Fog Lights

You will need to power your new mounted fog lights through a relay
You will need to power your new mounted fog lights through a relay | Source

Driving in fog. It sounds like the opening to a suspense novel.

Ever notice that if you put your headlights on high beams in heavy fog the light will reflect back at you? That’s the theory, at least, behind fog lights. They are usually amber in color so their reflection doesn’t glare back at you or at oncoming drivers. Fog lights also point down at the road immediately in front of the car and cast a wide, dispersed beam. That way you can see the ditch alongside of the road.

You shouldn't be driving fast in fog, so you have no need for high beams that are aimed far ahead of the car. That’s why factory fog lights are wired to switch themselves off as soon as you turn on the high beams. They presume you left the fog bank. Now you know.

Even if you forget all that meaningless detail and trivial knowledge, fog lights just look cool on some cars. As easy to mount as the horns we talked about, you will have to power your fog lights through, you guessed it, a relay. You might want to buy a few of those little relays at the parts store. They're cheap.

Install an Amplifier

Amplifiers increase the power output of your car’s sound system, as their name might suggest.
Amplifiers increase the power output of your car’s sound system, as their name might suggest. | Source

So driving in fog isn’t your thing. I don’t blame you. But having some loud tunes and some great, deep bass sound inside the car will put anybody in a good mood. And if you don’t think fast-tempo music makes people drive fast, ask your grandparents how many speeding tickets they got listening to Zorba the Greek on their car radio.

Amplifiers increase the power output of your car’s sound system, as their name might suggest. They are easy to hook up, so just take one of your handy relays and kiss those highway blues goodbye.

Install a Heavy-Duty Battery


Amplifiers draw an amazing amount of current. Their appetite for electrical power is voracious. You will know that because they get hot when in use, and heat is a byproduct of energy usage. It seems that people that have those big, powerful sound systems are usually plagued by battery problems. Maybe their engine’s alternator is not up to task for supplying all that power to the amplifier so it pushes the load off onto the hapless battery.

Either way, it’s always nice to have some extra battery capacity, even if it’s just because you left the lights on all day at work.

Install Auxiliary Gauges

A very common mod in years gone by when cars only had warning lights in their dashboards, aftermarket gauges would be a nice addition to that antique you call a resto mod. As if that changes anything, right? What’s in a name.

Anyway, if a simple panel of vital indicators would look good on your car, don’t be afraid to order up a nice set. No relays required. The wiring is straightforward and intuitive. Trust me. What could possible go wrong? Well, maybe you should read the instructions that come with your new gauges. Enough said.

Install an Auxiliary Engine Cooling Fan

Definitely needing a relay or two, these are a great idea if your car tends to run hot when idling in traffic. Simple to install and a little more involved to wire up (but you can still do it), an extra cooling fan is extra insurance for that expensive engine under the hood.

This article is accurate and true to the best of the author’s knowledge. Content is for informational or entertainment purposes only and does not substitute for personal counsel or professional advice in business, financial, legal, or technical matters.


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    • profile image

      steven B 

      13 months ago

      extra fan setup seems legit lol I'm definitely going to try it. i got a lot of these upgrades already. i get all those bits and pieces from got it from a VW forum back in the day pretty cheap prices. anyone has pics of their fan install ?

    • profile image

      David Carrizales 

      16 months ago

      How do you wire a toggle switch for windshield wiper motor

    • WheelScene profile imageAUTHOR


      2 years ago from U.S.A.

      Wow a 93 Vette! We want to see it, share to: so we can share it with our readers!

    • c1rca profile image


      2 years ago from USA

      This is a great informative read, thanks for sharing!! Maybe it's time I try to work on the spark plugs on my 93' vette!


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