Electrical basics, tips and safety

[OutToWinPAHC]

Let me explain my background first. I am not a mechanic, I don’t work on cars for a living. I am an electrical engineer who works on high voltage / high current industrial electronics. I do most of my work live on systems 208/480/600VAC that carry anywhere from 20-2000amps per phase with millions of watts of power being supported by them. Vehicle electrical is cake to me.

In my time tinkering with cars I have come to know one thing. Most electrical problems are self induced. Granted mechanical devices fail, cutting harnesses, and relays can lock but other then that there’s not much to go wrong. Most problems are caused when someone is trying to wire something, they wire it improperly, or botch the install.

Understanding DC….A vehicles electrical system is designed to run off of DC. Most cases +12volt with a floating ground, though others exist. DC stand for direct current, and this is represented by a positive and negative. The positive which is the positively charged part of the atom, the proton. The negative which is known as the Neutron, and the flow between the atomic transfers known as the electron.

In the vehicle the negative of the battery is connected to the chassis. The positive is usually fused before going to the device. When the device is energized electrons flow from NEGATIVE, through the device and back to POSITIVE. So the positive is the fused return path.

Simple ohms law defines 90% of the electronics of the vehicle with the exception of injector pulse width modulation and how the alternator works.

Ohms LawI am not here to teach this, but electricity has 3 very basic parts... Voltage –E, Current – I, and Resistance -R. E= IxR. As current decreases, current will increase. As voltage increases, without a change in resistance current will increase. Current is AMPS, A short is a low or no resistance connection.

Safety12 Volts is small, soaking wet you can touch the battery and not get shocked. Your bodies internal resistance is too high to feel the effect. But batteries pack a punch in short circuit current. Usually 1500-3000amps of instantaneous power that will melt metal, and give you third degree burns if you’re holding that metal. ALWAYS DISCONNECT THE BATTERY. The safest method is the negative first because it takes away the potential of hitting the chassis with the wrench. If you hit the chassis with the wrench while unbolting the negative nothing will happen. Do it to the positive your going to have a hell of a short. Insulated tools are nice, but tape up your wrenches to save cash.

ToolsI don’t expect you to have all the gadgets and tools I have. But a multimeter is your best friend. Unless you’re troubleshooting the ECU readings, you can get away with a basic one. I suggest you buy one.

FusesAlways fuse added electronics. Always replace with the same size. If the fuses blows there was a problem don’t just replace it, trouble shoot first. Pull the fuse and check each side of the socket to ground with you meter on ohms. If both sides of the fuse read high 1000 ohms or more, you’re good. If one side is low 1 ohm or less, you have a short and need to trace the circuit out. The fastest way to check fuses….. When you look at a fuse you can always see a tab of metal on each side. So just check across the fuses with the meter on ohms and look for less then .5ohms.