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Repair Car Electrical Problems
You gain a particular skill when you learn to repair automotive electrical problems. This portion of the sp88.co.uk website will further address various vehicle problems.
These individual articles address typical issues with popular autos. These helpful auto repair articles are included at the bottom of the page. First, however, we ask that you take a moment to read these informative posts.
This page will discuss why learning to repair automotive electrical faults is such a valuable life lesson. We’ll also provide resources used by automotive training programmes to teach pupils. In addition, towards the end, I’ll reveal my secret weapon for rapid electronics learning.
Diagnosing Car Electrical Problems
When automotive teachers educate students on how to detect car electrical problems, they retrain the students’ brains to think logically.
In a methodical step-by-step process, we execute successful electrical diagnoses. This discipline has applications in various areas of automobile diagnosis.
After resolving a few complex automotive issues, the mechanic quickly finds that by employing these techniques, there is almost nothing they can’t diagnose and repair.
This includes Chevrolet dome light issues and problems with domestic appliances such as washers and dryers that use identical switches, relays, and circuits. As the year’s pass and your diagnostic skills improve, you’ll find yourself relying on them to address other difficulties in your life.
Do you already know a lot about this topic? Then I dare you to take this 7-question automotive electrical exam. If you get them all right, you should be good to go for the ASE A6 electricity and electronics certification examinations.
Now that I’ve discussed why learning to repair automotive electrical faults is essential. Let’s look at some methods to master these skills on your own.
Self-taught students are frequently more effective than individuals who have spent thousands of dollars on formal automotive training in fixing complicated automotive problems.
Electric Car Service & Electric Vehicle Repair Shop in London
Electric cars are becoming much more prevalent on our roads. When Electric vehicles were initially introduced, they were far too expensive for the typical driver to purchase, but things have changed significantly since then. Modern Electric cars are far more efficient, less costly to maintain, and more accessible than older versions. Electric vehicles are now much more prevalent on our roads because of these advancements and a considerable rise in environmental awareness among drivers.
However, most individuals believe they must take their electric vehicle to a dealership for repairs. An extremely pricey choice! We have worked with electric vehicles at Woodstock Motors for more than 35 years. And, We began fixing milk floats for a nearby dairy 35 years ago, and since then, we have worked on nearly every type of electric vehicle.
We offer first-rate electric car services for all major brands.
Additionally, we have the most extensive knowledge in London of electric vehicle repair. You can rely on us to repair or service your hybrid or electric car, whether made by a well-known company like BMW or Toyota or an electric-only brand like Tesla or G-Wiz. Our mechanics have received thorough training in maintaining EVs. Bring it in so we can examine it. A word of warning: EV manufacturers occasionally make it impossible for anyone other than themselves to fix your car. If this is the case, we’ll let you know before we get started because, in most cases, we can tell you over the phone whether or not we can be of assistance to you.
Call us for electric vehicle service and repairs in London.
Diagnose electrical problems by chasing voltage drops, instead of the old-fashioned way — checking continuity. Including Mike Allen’s Physics 101 introduction to Ohm’s law.
Instead of the traditional method, Diagnose car electrical faults by chasing voltage drops — checking continuity, including Mike Allen’s Physics 101 introduction to Ohm’s law.
The road in front of you seems to go on forever. Even the bravest Saturday mechanic would want to stay off the road and secure at home, given how dark and gloomy it is today. You still have hours to go before you reach your objective, unfortunately. Nothing is visible except for the tiny puddle of light generated by your headlights. And it looks like that puddle is growing smaller. And more yellow. One of your headlights is as yellow as the toenails of Satan, so a simple trip to the convenience shop for petrol and a quart of carrot juice identifies the problem.
You’ve got a voltage drop.
Back to Basics
In particular, when it comes to wiring for automobiles, electricity shouldn’t be intimidating. Even if you’re wearing damp sneakers, the simple direct current (DC) doesn’t have enough power to make your toes tingle. Maintaining an electrical system isn’t as simple as maintaining a mechanical one. Think of a carburettor’s linkage. Do you recall carburettors? Carbs are simple to comprehend. When you wriggle the throttle linkage, it is broken if one end moves but the other does not. Likewise, it’s stuck if you jiggle one end and neither end activities.
Additionally, it must be greased if it is difficult to move. On the other side, electrical-system diagnosis is one step removed because you cannot see the electricity in the wire as you can see the linkage swaying. You may perform a basic electrical diagnosis with only a trouble light. I have a few danger lights, and I always utilise them. However, diagnosing anything more complex than a burned-out bulb requires more powerful tools. Use a voltmeter, please. Or, to be more precise, a DMM or digital multimeter. You can get a decent one for approximately the cost of two pepperoni pizzas.
Meeting With Resistance
To your dim headlamp once more, The voltage available to the headlamp is decreased by resistance in the circuit. You can locate the additional resistance using the DMM’s ohmmeter scale, right?
Wrong. We are searching for extremely small resistances, frequently less than one ohm. Your DMM’s resistance (ohm) scale likely bottoms out at 200 ohms, making it challenging to measure single-digit values. Use the voltage scale instead, which most DMMs can accurately measure to a few millivolts. Let’s get going.
Start by turning on the problematic circuit, in this case, the low beams of the headlights. We’ll now check the voltage of the battery. The precise figure you observe when measuring across the battery posts is what we need to know. And by lead posts, I don’t mean the clamps. The voltage should be between 12.5 and 12.8 volts if the battery is fully charged.
Check the connector on the dim headlight by back probing. Your DMM’s black lead needs to be connected to a reliable ground, ideally the battery negative post. The voltage you measure at the low-beam lug is around 11 volts. That’s less than our system voltage, which is around 12.5; yet, more is needed to account for the significant dim-out. Check the ground lug at the bulb connector right now. Surprise! The metre shows about 4 volts when it ought to show 0. This suggests that there is resistance in the wiring on the ground side, leaving the filament with only 7 volts.
The first lesson is that electricity constantly circulates in a circle and that the hot and the ground sides are equally significant.
The second lesson Utilize some systems analysis. For example, you can bypass troubleshooting any circuit components shared with the working headlamp since just one of them is dim.
When you’re metering the ground side, the voltage on the metre suddenly rises. And it doesn’t jump to the 11 volts we saw earlier; instead, it jumps to 12.5 volts, which is exactly what we can measure at the battery. At the same time, the light bulb burns out. What happens next?
You are measuring the total battery voltage. That suggests there is a break in the circuit somewhere between the DMM positive probe and the battery ground. The voltage would be zero if the opening were caused by a burned-out filament or a damaged wire on the hot side. Indeed, the open is on the ground side. In that ground circuit, what was formerly a resistance of roughly 1 ohm has suddenly become available with almost unlimited resistance. Culprit? It’s a damaged ground wire, most likely caused by someone pushing a pointed test light or metre probe through the wiring years ago to investigate an issue.
The hole in the insulation allowed water to enter the wire, transforming it into green, high-resistance corrosion and finally leading the wire to collapse.
Another thing to remember is never to punch a hole in a wire to test a circuit. So you change the wiring. The problem is solved until you go around to check the lights in front. They’re now both the same colour. When you wake up the dim one, you notice they’re both less than brilliant—which I’d anticipate when I measure 11 volts at the bulb socket instead of the 14 I’d expect when the engine is running. The circuit still has a resistance, but it’s between the battery and the bulb this time. So I am returning to the DMM.
Measure the distance between the positive post of the battery and the clamp. There should be a tiny voltage present. When the lights are turned on, the overall drain on the battery is 15 amps or higher. Any resistance between the clamp and the post will result in a voltage loss. It should just be a few millivolts. One metal-to-metal junction at a time, chase the circuit toward the bulb. Probing between the input and output of the headlight relay reveals a rough volt decrease. Inserting a new relay reduces the reading to a few millivolts. And both headlamps are on full blast.
The problem was resolved.
Warning: Math Alert
According to our calculations, your 55-watt headlamp bulb uses 4 to 5 amps from the car’s electrical system and has a resistance of roughly 3 ohms. Our low-cost problem light has a resistance of 10 to 12 ohms, which means that if we insert the probe into a circuit, it becomes a part of the circuit, affecting the values we’re attempting to investigate. Our DMM has a resistance of nearly 10 million ohms; therefore, adding the metre probe will not change the voltage in a circuit. When troubleshooting, performing this testing with the course turned on, and operational is critical.
Assume our corroded wire was on the positive side of the headlamp circuit rather than the ground side. And because the battery is low, you remove the connector from the bulb and metre the socket. If the wiring is OK, you should see full system voltage on the metre, so everything should be fine, right? But here’s our broken wire, with an internal resistance of one to three ohms. You’d think the metre would display lower voltage, but you’d be wrong. The current passing causes the voltage to drop through the circuit. The DMM draws no current due to its megohm impedance, and you will read the entire system voltage until the course is loaded down.
More than a few hundred millivolts of drop across any connector bother me. Whether a dome light drawing 500 milliamps or a starter pulling 200, the overall loss in any circuit should be at most 1 volt.
Physics 101: Ohm’s Law
First rule of working on an automotive electrical system: It’s only 12 volts, and you can’t get a shock. (Well, except maybe from the spark plug wiring, but I digress.) Second rule: The second rule isn’t just a rule–it’s the law. Specifically, Ohm’s law. Don’t freak; I’ll go slow with the math.
I=V/R, where
I=the current flowing in a circuit
V=the voltage that pushes the current
R=the resistance in the circuit
An example: A headlamp low beam normally draws 4 amps or so when it’s switched on. (That’s the current.) The voltage is around 13 to 14 volts when the engine is running. So,
4=14/R, where R is the resistance of the filament in the bulb. Solving for R, we get 14/4, or just under 3.5 ohms. Imagine that one headlamp is kinda yellow compared to the other side. We measure the voltage at the lamp socket, and it’s only around 7 volts, explaining the dimness. I’ll leave the math for homework, but that means there’s another 3.5 ohms of resistance somewhere between the battery and the headlamp. The circuit, with its extra resistance, will now have a total resistance of 7 ohms for a current draw of 2 amps, and it’s our mission to find that resistance and repair it. Another example: The starter motor draws 200 amps (roughly) when the engine is cranking, usually when the battery voltage is only about 10 volts. So,
200=10/R, making R=0.05 ohms
Similarly, if we know that an electrical device has a resistance, we can figure out how much current it will draw. Installing a new set of eight clearance lights on the travel trailer? Measure one bulb with a really good ohmmeter, and it measures 12 ohms. You can figure on roughly 1 amp of current. Multiply that by 8 running lights–your new lights will draw a total of 8 amps. Add in the running lamps, and the 10-amp fuse on that circuit may not be enough.
Trust me; these numbers will always work out correctly. If they don’t, you’re missing something.
