Sam Memmolo
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Electricity 101 Bobit Publishing Co. Truck & SUV Performance For those of you who may not know, in addition
to the TV show “Two
Guys Garage”,
Our collective goal was to become a valuable resource for automotive folks. What’s the point of this diatribe? It’s simple. None of the above would be possible without electricity and the technology that has exploded in a very short time. We live and die by “ISDN” lines, high speed internet connections like “DSL” and “T-1”, not to mention some pretty sophisticated hybrid radio gear. A lot of this incredibly valuable electronic technology has found its way into the vehicles we drive today. What’s more remarkable, is the fact that this stuff actually “Lives” in the harsh automotive environment. Computer controls and their related sensors made their production debut in the late 70's, and became full bore engine management systems by the late 80's. Initially, these electronic controls were found in gasoline powered passenger vehicles, and then eventually made their way into light trucks. Today we have full electronically controlled diesel engines in pickups, large SUV’s, and even in large over the road class 8 trucks. It’s easy for these components to live in the sanitary environment offered by
the radio station. No smoking near the equipment, fully air conditioned rooms to
keep the gear cool and dry, and no vibration. No need to be a Mensa to figure
out how much abuse those same components must endure when mounted under the hood
of your diesel 4x4! As you would suspect, Dave and I receive a large percentage
of calls regarding electrical problems. Everything from “It won’t crank over”
all the way to “it starts but runs awful”. These problems are compounded by the
fact that most electrical problems are intermittent gremlins. No matter how sophisticated these systems may appear, they still operate using basic electricity and electrical fundamentals. Bad ground connections account for a large percentage of these electronic aliments in automotive environments. In a series of articles here in TSP, I’ll attempt to clearly explain how most of these “gremlins” can be uncovered. When it comes to checking for electrically good ground circuits, forget about your ohmmeter. Use a voltmeter set to a low voltage or millivolt scale. Using your voltmeter, you can more accurately check the ground circuit. I’ll explain in more detail as we get farther along with logical diagnostics, but the first rule of electronic diagnosis is to fully understand and know how to check the power source. I’m referring to the Battery First let’s establish the battery’s role. The most common are lead-acid batteries, but the newer “Maintenance Free” types use calcium also. The latest technology is the new “Spiral Cell” batteries that are spill proof and leak proof. Let’s start by verifying the battery’s rating.
Batteries have been rated using several different methods. The “Amp-hour
Capacity” rating represents the steady current (amperage) the battery will
deliver for 20 hours at 80 degrees F, without the terminal voltage dropping
below 10.5 volts (for a 12 volt battery). Most of today’s batteries are rated in “CCA”, (Cold Cranking Amps) the amperage figures for this rating may be listed as 450, 500, 550, etc. These figures represent the current (ampere) flow a battery can deliver for 30 seconds at 0 degrees F while maintaining a terminal voltage of not less than 7.5 volts. It’s very important that the battery has enough “Cold Cranking Amps or Amp-hours to handle the electrical requirements of the specific vehicle. An under capacity battery can test fine, but be a source of problems due to an unstable voltage platform. Most good batteries have the CCA ratings listed right on the manufacturer’s label. Any battery retailer can supply you with the specific requirements of your vehicle. Next, the battery needs to be tested to be sure it can deliver the required amperage and voltage. The most common test has been the “Load test”. There are 2 parts to a basic battery load test.
Remember, it’s the voltage regulator that senses when to reduce the charge output. If the battery has low energy storage, and the surface voltage is too high due to sulfation or other ailments, the voltage regulator will sense the high voltage, think the battery is full, and reduce the charge rate from the alternator. There are a few other battery ratings including
“Wattage” and “Reserve Capacity”. Again, new technology has found its way into the automotive world that was originally developed for the cellular phone industry. The new technology is called “Conductance Testing”. The diagnostic equipment sends a small current through the battery and with calculations based on algorithms, accesses the battery’s condition. This testing has several distinct advantages, including accuracy, speed, and the ability to test a battery in a low state of charge. The Midtronics tester is excellent, and I use mine often. Here are a couple of safety reminders. This may seem like a lot to digest, but it will give you a solid foundation as we build on solid diagnostic techniques in subsequent articles. Happy Motoring! Sam Memmolo
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I also host live call-in
These gremlins are
responsible for a lot of grey hairs on technicians and do-it-yourselfers alike.
Most of the calls Dave and I field include horror stories about diagnostic
nightmares, lots of expensive components replaced with poor or no results, and
cars or trucks that have been unusable for extended periods of time. I’d like to attempt
putting this all in perspective.
Truth: The vehicle’s electrical needs are supplied solely by the battery.
Myth:
The vehicle runs off of the Alternator. The alternator’s only job is to keep the
battery full, not run the vehicle.
Batteries emit
explosive gases, so be careful when working around them, avoiding any kind of
spark, arc, or other ignition source.