Finding Automotive Wiring Diagrams

As an owner of a car, I find myself becoming educated on the subject of automotive wiring. Since I am just about the last person who should be playing with anything that has electrical current running through it, I was hesitant to attempt to tackle the issue of automotive wiring.

However my vehicle decided otherwise when it started to randomly select electrical systems that it wanted to me tamper with. When the electric seat belts started to slide back and forth without reason as I drove down the highway, I decided I better figure out how to tamper with the electric systems, considering the exuberant rate of automotive repair.

I found myself with a decision to either, break down and spend $100 an hour for a so-called expert to look at it and try to repair it, or I could learn how the electrical system of my car worked. Considering my level of ignorance I probably was going to try to conquer the impossible. After all the only thing I knew about electrical systems is that AC/DC was a rock band and that dummies and wiring usually did not get along.

However despite my reluctance, I set out to learn what I could about automotive wiring. I quickly learned that there is a huge supply of information available on the subject of automotive wiring. A quick search on Google provided me with an array of information. There are many different levels of sites offering information.

Some sites provided a basic overview of the average electrical system of most cars. A company named Long Island Customs offered some great basic information. They stated that their information was simply for a basic understanding and not for a detailed explanation of particular models. However they actually provide some thorough information on basic systems such as AC and lighting. They also provide some great trouble shooting information.

Another site for general information on electrical systems is This educational website offered general programs on electrical systems in their integrated publishing section. considers itself the leading source of professional diagnostic information. They offer full diagnostic flow charts of automotive electrical systems. Their charts offer both system and component perspectives.

I found a great site for individual systems that covered all American made cars from 1985 to 2009. breaks it down by system, such as headlights, computer data lines and AC systems. Their individualized charts start at $5.99. They also offer information on 1960-1984 models starting at $6.99. They print the information into an Adobe PDF document and offer rushed service guaranteed to provide you with the diagrams for your particular car in less than 24 hours. offers a basic explanation of electrical information in an MS Word document; however they do not supply charts or schematics.

Two other sites that I found to offer great information were and provides complete color diagnostics for most makes and models. What I found interesting(?) is freeauto will provide you these color automotive electrical charts and all the other information on their informative website for $11.99. They also assist you with basic electrical theory, electrical harnesses and test equipment. offers a CD-ROM that contains wiring systems for every car from 1979 to 2009, for only $17.98. They also offer CD-ROMs and instant downloads for specific models of cars. They only charge $14.98 for this information.

I also decided to look around to see if I could find manufacturers’ manuals that offer automotive electrical diagrams for particular makes and models. What I found was that Haynes Auto Repair Manuals offer a repair manual for just about every major make and model of car. These thorough repair manuals explain every system on particular models in an easy to understand format. I found that these manuals offer electrical charts for their models. I found Haynes manuals available at several sources including their own website for $24.95 and Barnes and Nobles for $22.95 with a membership. The best deal I found on these manuals was Books-A-Million, who offers most Haynes manuals for only $16.45.

So whether you are like me and you don’t know the first thing about automotive electrical systems or even if you are educated in electrical systems you will find these sources to be of great help. If you still desire additional information you may want to contact your local car dealer or mechanic.

How to Improve Your Automobile With Automotive Electrical Supplies

For many people buying a car is one of the biggest purchases they will ever make, second only to the family home. If you have parted with some well earned cash to invest in a motor vehicle then you will want to make sure that it is well maintained to ensure your safety, the safety of others and the longevity of your automobile. While many people are conscious of the importance of regular servicing in order to keep the engine running smoothly they may not be aware of the significance of a cars electrical system. There are many automotive electrical supplies required to run a vehicle efficiently and gaining an insight into these components will place you in a better position to maintain and improve your motor vehicle.

Sometimes when people buy a car, their budget may not be able to accommodate the many extra features available at the time of the initial purchase and while it is often recommended that extras are fitted to a vehicle at the time of manufacture, for many these may not be an option. Others may enjoy the challenge of buying an older car and restoring it to better than its original state. Looking into the range of automotive electrical supplies available for your vehicle may allow you to make ongoing improvements to your car as your budget allows.

One of the best places to begin looking into the range of products available for your cars electrical system is the internet. Here you will have access to manufacturers and suppliers of these parts and will gain a good insight into what is available, their function and how they can improve your vehicle. From here you can start planning how you can enhance your vehicle in order to maximise its safety and performance.

When dealing with a car’s electronics it is of great importance that such work carried out is done by a mechanic who is qualified in this field. Just as you would not entrust your home’s electrics to anyone but a fully licensed electrician you should never carry out automotive electrical work yourself or contract anyone other than a certified auto electrician to do the work for you. Auto electricians are specialised in the area of vehicle electronics and have a thorough knowledge of the automotive electrical supplies required for a particular job and have access to suppliers of these parts. In addition to this, if you get work done on your cars electrical system by a specialist in this area and something goes wrong you will be able to take advantage of any warranties that may apply to these parts which would otherwise be void if they are not fitted by an approved mechanic.

There are many ways you can improve your cars performance and if you are passionate about your vehicle then you may wish to look into the range of automotive electrical products available. You may well be surprised by how much you can actually enhance your automobile

Voltage Drop Testing – An Effective Method For Solving Automotive Electrical Faults

For any electrical component to work properly, it must receive the correct current flow. Low current to a light bulb, for example, makes the light dim. Low current to a compressor clutch coil reduces the magnetic field and may allow the clutch to slip or not engage at all. For proper current flow to exist, the circuit must have the correct source voltage applied, and be free of any “unwanted” resistance in the circuit. And the best way to test this is to measure voltage drop with the circuit “working”.

Here are the steps to take to perform a voltage drop test:

1. Connect your DVOM negative lead to the battery’s negative post.
2. Connect your DVOM positive lead to the battery’s positive post and measure its voltage. Record this reading.
3. Connect your DVOM positive lead to the positive side of the load being tested, as close to the load as possible.
4. Operate the circuit, and record your measurement.
5. Connect your DVOM positive lead to the negative side of the load being tested, as close to the load as possible.
6. Operate the circuit and record your measurement.

Let’s take a closer look at these steps. First, we want to test the integrity of the ENTIRE circuit so placing your test leads at the battery is a must. You can make an extension lead for your DVOM so you can always connect to the battery ground terminal with your negative meter lead. Second, it is important to know the source voltage available. If the battery is weak to start with, your circuit is already working with a handicap. Even better is to measure source voltage with the engine running, and use that as your baseline.

In the third step, you are making sure all that source voltage is arriving at its ultimate destination…the load. Getting as close to the load as possible insures you are testing the entire path. On the positive side of the load, you should read within 0.50 volts of your source voltage, i.e. if you started with 14.56 volts you should read no less than 14.06 volts. This applies to most basic circuits. If you are diagnosing a control module related circuit, you may want to look for even less than that.

In step #5, you are looking for unwanted guests robbing your load downstream. Remember, all the voltage potential should have been used by the load. If you get a voltage reading of 0.50v or more here, there is someone else at home stealing potential from the primary component. This unwanted source may be ultimately found way “downstream” of the load, maybe even at the battery connection itself. Even so, it will still cause the voltage reading at the load to be over 0.50v. This is due to the available voltage being split proportionally between the two, and tends to throw techs new to voltage drop testing off. Remember, current flow is instantaneous throughout the circuit. Again, in the case of module related circuits, a little less is better. Stay as close to the load as you can to make sure you check the entire ground path.
Remember, current flow is only going to happen with the circuit turned on and working. Don’t forget to operate the circuit when taking your measurements.

My Reading Is Out Of Range. Now What?

Experience is a guide here, as in all things. Typically, unwanted resistances are the result of poor grounds or poor connections, either in a harness connector or switch contact, and will result in an obvious, out of range measurement. To find the little unwanted guest, all you have to do is “backtrack” from your load back to the battery. Here, you will need to spend some time with a schematic for the circuit you are working on and use a little common sense. For example, if there are parallel branches on the circuit, are all branches affected? If so, focus on that section of wiring common to all. If not, focus on that section that is unique to the component you are diagnosing. Move back towards the battery at logical points (harness connections, switch contacts, splice points, etc.) until your DVOM reading is back to normal. That means you passed the unwanted guest and all you have left to do is narrow the search between your last two test points.

Some voltage measurement on the ground side of a working load is normal. If no ground exists at all, you will measure source voltage on both sides of the load. If the ground side measures 0.0 volts on the money, and the component is receiving correct source voltage, then the load likely has an internal open.

What if both sides of the load test just fine, but it still doesn’t work right? If you tested right at the load, there is only one area left untested…the load itself. In this case, you most likely have a failed component. A good example of this is a solenoid that is failed mechanically, not electrically.

Remember, too, to not take shortcuts in your initial tests. It is vitally important that you test the entire path the current is taking from and back to the battery. A common mistake is to use a chassis ground under the dash when testing inside the car. But don’t forget, that chassis ground point still has to make it back to the battery, typically through a few more connections, before the ground path is complete. That inoperative HVAC module could be simply a bad connection at the bulkhead connector or firewall ground eyelet, and you’ll miss it if you cut corners. Done properly, a voltage drop test will quickly isolate which side of the circuit has the problem, and save you diagnostic time in the process.

Electrical Troubleshooting On Cars, Should This Be A DYI?

Many malfunctions that occur in cars may be diagnosed as electrical problems. The cause is usually related to the electricity that is being generated by the battery or alternator. Troubleshooting can be a frustrating task, especially if you’re not knowledgeable enough.

A crucial consideration when working on automotive electrical systems is ‘safety’. Although the risk of being shocked is low, the danger is accidentally shorting out a hot circuit. This may lead to damaging the wiring, PCM or other onboard electronics – and fire.

Electrical Problem Signs

For your safety, and your car’s, it is best to let professional auto technicians handle the electrical troubleshooting. How do you know when it’s time to bring your sports car to a Maserati or Porsche workshop? Here are some of the signs you have to look out for.

Vehicle won’t start. It’s the most common electrical problem you will probably experience. If the interior lights aren’t working and the car won’t start, the problem is likely a dead battery. If you hear a clicking sound, it might be the starter. Go to an auto repair shop for final diagnosis.

Lights dim while driving. Does your dashboard or headlights dim when you’re driving at low speeds? There might be a problem with your car’s alternator, or voltage regulator. It could also mean that the battery is on its last legs, or have trouble holding a charge.

Visible battery damage. Even if you don’t know troubleshooting, you can still inspect the battery from time to time. Are there corrosion stains or buildup around the terminal? It may be a sign that the battery is leaking, experiencing a problem, or nearing the end of its life.

Brake lights don’t work. You tried having your break lights replaced, but it’s still not working. The problem may not be with the bulbs. It might be the fuse. It can also happen to some specific part of the vehicle. Let an auto shop check if you don’t need to replace a fuse.

Electrical System Service

If you’re an Aston Martin owner, the more you have to bring your car to a service center specializing in luxury vehicles. Batteries usually last between three and seven years, so it will be a smart decision to have it checked once you experience any of the signs.

Remember, the contents of the battery are corrosive, and they will damage bare skin. That’s why it should not be just a DIY task. There are dozens of components needed to route power in your vehicle’s electrical system. It can vary greatly according to vehicle make, model and age.