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Friday, March 23, 2007

Tech Tips: Electronics

Tech Tips: Electronics
- by Dan Marinucci, Technical Trainer

Are you witnessing an increase in complaints about . . .

Dead batteries?
Intermittent warning lights?
More electrical complaints in general?

The implementations of electronics operating in manufactured automobiles today (and of the future) continue to evolve into more sophisticated operations. Working on these automobiles can be challenging and even frustrating due to the numerous electronic systems which operate the vehicle.
Sometimes it seems the electronic vehicle simply has its own agenda. Whether the vehicle’s agenda is to annoy its owner or frustrate you, the technician, you need a game plan to cover the basics of the electrical system.

90% of repairing cars is staying focused on the basics. Automotive electrical basics are:

Connection condition
Battery condition
Alternator condition

Connection condition
In order of importance, connection condition (at least to the battery) really does come first. Without a good solid connection to the battery the vehicle may not start, charge or it could generate a few unwanted electrical gremlins. Clean tight connections from the battery to the chassis grounds, to the alternator and to the starter motor will eliminate subtle electrical gremlins. The condition of all electrical connections and the circuits they connect to can be easily tested using the voltage drop test. You will find bad relays, bad fuses, poor connections and faulty ignition switches within minutes (opposed to hour or days.) This may be the single most important test for technicians to implement into diagnostic routing when searching for a cause to an intermittent electrical complaint.

Battery Condition
Battery condition is paramount on today’s vehicles because the on board computers will be the first to react to a problem within the battery. Computers are reliant on continuous, uninterrupted current flow between the positive and negative terminals of the battery. One bad plate in the battery can cause a multitude of electrical problems after you start the engine. You may be thinking, “That’s odd, I thought if the battery was bad the starter motor wouldn’t crank the engine?” Not true. As a technician on today’s vehicles, you need to toss out this old thought process. Before addressing electrical complaints on late model vehicles check the condition of the battery to ensure it is not the cause of the current fault.

Alternator Condition
After a battery has been determined to be in good condition, you will need to determine the condition of the alternator. With the numerous electronics operating late model vehicles, the alternator output on some cars may exceed 200 Amps! With that much output the main power lead to the alternator may be fuse protected. Before replacing an alternator because of “no output” - double check the manufacturer’s information regarding their test procedures. You may discover that a fuse, fusible link, or specially designed cable is the cause of the no output problem. One other note, be advised that some late model vehicles could have alternators that are networked and diagnosing them will be different.

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