Finding a power source is a basic skill that is necessary for every motorist planning to install additional equipment. Whether it’s mounting an alarm, connecting a DVR or installing a new acoustics, correctly identifying a plus contact is critical for safety. An error in determining polarity can lead to short circuit, fuses burning, or even wiring fire.
In today’s automotive electrician, there are many wires braided in the same insulation, which often confuses beginners. However, using the right tools and methodology, it is possible to identify the contact correctly. In this article, we’ll break down the proven ways to find a plus that professional installers use and explain why relying on the color of the insulation alone is a bad idea.
The main purpose of any connection is to provide a stable voltage without the risk of damaging the regular systems of the car. Plus wire It carries the potential from the battery or generator to the consumer, and finding it requires care. We will consider working with a multimeter, a control lamp and specialized probes so that you can choose the most convenient method for yourself.
Why you can’t rely on the color of the wires
Many beginners make the mistake of relying solely on the color of insulation when seeking food. It is commonly believed that a red wire always means plus, and a black wire means mass. While this rule often works in factory wiring, in reality, things are much more complicated. Cars of different brands, years of release and markets can have completely different color codes.
You can also not rule out the possibility that the car has already been changed. The previous owner or alarm installer could use a different color wire to connect the equipment. Therefore, visual assessment is only the primary stage, which must be confirmed by instrumental verification. Color marking It is a guide, but not the ultimate truth.
Sometimes wires can be faded, contaminated or have non-standard insulation, making the visual method even less reliable. In old cars, the wiring can be twisted, and the harnesses can be chopped over. The only way to be 100% sure is to use a measurement device. Ignoring this rule can cost you expensive repairs of the electronic control unit.
⚠️ Warning: Never make twists or connections based solely on the assumption of the color of the wire. Always check for voltage and polarity with the device!
Necessary tools for on-board network diagnostics
For high-quality and safe work, you will need a minimum set of tools that every motorist should have. The main instrument is multimeter. It allows you to accurately measure the voltage, check the integrity of the circuit and determine the presence of current. Modern models are compact, have protection against overloads and a clear interface.
The second important tool is the control lamp, or "control". This simple device, consisting of an incandescent light bulb and two probes, allows you to quickly determine the presence of voltage. Unlike a multimeter, the control lamp shows not only the presence of potential, but also the ability of the circuit to give current under load. This is especially important when looking for places to connect powerful consumers.
You will also need auxiliary materials: insulation tape, a set of screwdrivers, bokorez and, possibly, circuits of electrical equipment for your car model. The presence of the scheme significantly accelerates the process of finding the right wire in the tourniquet. If there is no scheme, you will have to act by the method of vertebrae and logical analysis.
It is important to monitor the serviceability of the multimeter probes. Damaged insulation on the probes can lead to accidental closure of contacts in a tight wire harness. Before starting work, be sure to check the operability of the device on a known voltage source, for example, on the battery terminals.
Methods of search plus multimeter
Using a multimeter is the most accurate and safest way to determine the plus wire. First, you need to switch the device to the constant voltage measurement mode, designated as DCV or V-. The measurement limit should be 20 volts, as the voltage in passenger cars is about 12-14 volts.
The black multimeter probe securely fastened to mass car. Any unpainted metal part of the body or engine can be used as mass. Use a red probe to check the wires you are interested in. If the display displays a positive voltage (for example, +12.5 V), then you have found a plus wire.
If the instrument shows a negative value (for example, -12.5 V), this means that you have confused the polarity of the probes, or the wire being tested is negative relative to your reference point. In automotive electricians, this is rare when looking for power, but it is possible when diagnosing complex circuits. The main thing is the presence of tension relative to the body.
☑️ Multimeter check
When searching for a wire in a tourniquet, you can gently puncture the insulation with a thin sting of the probe if the wire is not available for direct contact. After checking the puncture site, be sure to isolate. This method is good because it does not require cleaning of wires, but requires care so as not to damage the veins.
⚠️ Warning: When working with a multimeter, make sure that the probes do not slip and close two adjacent wires. This can cause short circuits and failure of the electronics.
Finding a plus with a control lamp
The control lamp is a “grandfather” but extremely effective method that is often used by experienced electricians. The principle of its operation is simple: one end of the control wire is connected to the mass, and a sharp probe at the other end touches the checked contacts. If the lamp lights up, plus it is found. The brightness of the glow indicates the quality of the contact and the ability of the chain to carry the load.
The advantage of the control lamp over the multimeter is that it simulates the load. The multimeter can show the presence of voltage even on a “snotty” contact with high resistance, where the real consumer simply will not turn on or will work incorrectly. The lamp will immediately show whether this point pulls an additional device.
But there are nuances. Modern cars are packed with electronics, and using a powerful control lamp (like 21W) can damage sensitive control units. To check circuits going to computers, sensors or a CAN bus, it is better to use a high-resistance LED probe or still a multimeter.
How to make a simple control with your own hands?
Take a cartridge for a 12V light bulb, solder two wires 30-40 cm long to it. At the end of one wire solder the clamp "crocodile" (for mass), and at the end of the other - a needle or sharpened nail to pierce the insulation. All connections are carefully isolated.
When using a control lamp, it is important to choose the right grounding point. If you connect the "minus" of the controls to the wire, which you plan to check yourself, you will get a false result. Always start your search by checking the battery’s control lamp to make sure it’s working.
Table: Comparison of Plus Search Methods
To make it easier for you to choose the right tool for a particular situation, we have prepared a comparative table of methods. Each of them has its own advantages and limitations depending on the working conditions.
| Method | precision | Safety for Electronics | Speed of operation |
|---|---|---|---|
| Digital multimeter | Tall. | Tall. | Medium |
| The control lamp | Medium | Low (risk of overload) | Tall. |
| LED probe | Tall. | Tall. | Tall. |
| Visual (color) | Low. | Tall. | Instant. |
From the table, it can be seen that the multimeter is the most versatile tool. It combines high accuracy and safety. A control lamp is good for power circuits where you need to know if the wire holds current. LED probe is a compromise option, convenient for rapid diagnosis.
The visual method should be used only as an auxiliary method. It is absolutely impossible to rely on it when installing expensive equipment. An error in the definition can cause you to apply 12 volts to a 5 volt input, which will instantly disable the device.
Features of the search for a constant and impulse plus
When installing an alarm or auto-start, it is important to distinguish between two types of plus wires: permanent. +12B and pulsed (appears when the ignition is turned on). The permanent plus comes directly from the battery and is present in the car always, even when the key is removed from the lock. The pulse plus appears only in the position ON or ACC.
To find a permanent plus, check the wires when the ignition is turned off. If the multimeter shows voltage, it is a candidate. To check the pulse wire, turn on the ignition and find the wire on which the voltage appears only at this moment. This is important for the proper connection of immobilizer bypasses or auto-start systems.
Use the Min/Max function on the multimeter if you are looking for a pulse signal. It will record voltage surges, even if you are not looking at the screen at the time of ignition.
Some circuits may have a power outage delay. For example, in modern cars, the radio or windows can remain active for several minutes after the ignition is turned off. To avoid making a mistake, wait 10-15 minutes after turning off the key before the final check of the "permanent" plus.
⚠️ Warning: Connecting devices requiring constant power to a pulsed plus will cause battery discharge or inoperability of the device memory function.
Typical errors and precautions
One of the most common mistakes is to find a plus "at random" by closing the wires. This method, often referred to as the “pumpkin method,” is strictly prohibited in a modern car. Closing the plus on the mass or on another wire can cause the combustion of tracks in the assembly unit, failure of the ECU or fire.
Also, there is often an error of incorrect selection of the grounding point for the device. If you are looking for a plus, but your minus probe is hanging in the air or touching plastic, the device will not show anything. Make sure that contact with the mass is reliable: clean a small stain on the body to the metal before connecting.
Another important aspect is protection against short circuits in the process of operation. When you clean the wire for connection, try not to damage the neighboring wires in the tourniquet. Use an insulation tube (cambrick) to protect the connection site. Don’t leave bare twists, even if they seem safe – the vibration of the car can break the insulation over time.
Safety comes first: Never test for voltage by closing wires on each other or on the body. Use only measuring instruments.
Remember that in some cars, plus wires may be in unexpected places, such as in connectors under a torpedo or in door harnesses. Be careful and methodical. Haste is the main enemy of the electrician.
Frequently Asked Questions (FAQ)
Can you find a plus without tools, just by spark?
It's not recommended. The method of "spark" (closing the wire on the body) is dangerous for the electronics of the car. The spark creates a powerful electromagnetic pulse that can damage sensitive microprocessors. In addition, it is possible to accidentally close the wire going to the airbag or ABS, which will result in expensive repairs.
What if the multimeter shows 0 volts on all wires?
First of all, check the multimeter itself and the integrity of its probes. Then make sure you find the weight (minus) correctly. If everything is in order with the device, perhaps the fuse that feeds this chain has burned, or the wire has broken. Check the fuses in the mounting unit.
Can the plus wire be blue or green?
Yeah, maybe. Although standards require certain colors, manufacturers often deviate from them. In different models of cars, the same wire can be painted differently. Always check the voltage with the device, and do not blindly trust the color of the insulation.
How to find a plus if the wiring is shaved and flowers are not visible?
In this case, only the method of vertebrae from the source (battery) or from the consumer will help. You need to turn off the battery, ring the circuit on integrity, and then, connecting the battery, check the presence of voltage. Using the electric circuit of the car here will be extremely useful.