Things It Took Me Years to Learn By Bob Jeffries For all the years I worked in tech service fielding troubleshooting calls you would think that I’d have gotten to a point where I had heard every question conceivable. Eventually I expected to hear a question like “‘as I speed the alter- nator up on the test stand, the faster I go, the more the output drops” and be able to reply with a stock answer such as Number 27—“Slip rings out of round causing brush bounce, thereby causing the brushes to spend more time in the air and less time completing the rotor circuit, which will result in reduced output.” It just didn’t work that way. I have come to the sorry conclusion that given a mechanical device consisting of two or more parts, the amount of things that can and will go wrong are limitless. Troubleshooting can result in hair loss, sleep disorders and loss of appetite. Therefore, as a for- mer mechanic, I will share with you the tips I have learned from mistakes, trial and error, and wise old sages. Ask the driver of the vehicle every- thing you can. Anytime you have a failure and you have an opportunity to talk to the person who was working with the equipment when it failed, consider it your lucky day. This is comparable to having an eyewitness to a crime. Ask questions like “what were you doing when the alternator failed?” This may tell you if the way the machin- ery was operated contributed to the failure. “Are you the person who nor- mally operates this piece of equip- ment?” Sometimes lack of familiarity with a particular piece of equipment may cause a failure. “Has this vehicle been in the shop for any repairs or serv- ice lately?” Normally rebuilding a trans- mission doesn’t cause alternator prob- lems, but if they forgot to reinstall a ground strap when they reinstalled the transmission, it can. These questions and others like them should be consid- ered important tools in your trou- bleshooting repertoire. Assume nothing. The easiest way to waste time when troubleshooting is to abandon a systematic approach to trou- bleshooting. It would seem logical to assume that if you had three starter fail- ures recently on three identical vehicles and you get a “no start” call on an identical fourth vehicle, the problem is probably the starter. The natural reac- tion would be to go ahead and R&R the starter. Now, when you go to start the vehicle you still have a no start condi- tion because this time the problem was dead batteries. Think it doesn’t happen? How do you explain the new returns we often get across the counter? There is no such thing as a mechanic in a bottle. Belt dressings stop slipping belts by attacking the com- pounds in the rubber, thereby shortening belt life. Battery additives contain sulfu- ric acid that boost the battery’s voltage, but also make the acid content of the battery so strong it shortens battery life because of plate breakdown. These products should be eyed with the same suspicion used when viewing an enve- lope with Ed McMahon’s picture on it. Radio shops are the last place to contact when you have noise interfer- ence. Every radioman is trained from birth to reply “the alternator has a bad diode” anytime you have radio noise complaints. What you need to know is that there are two kinds of noise: con- ducted noise that is passed through the wiring to the radio, and radiated noise that passes through the air and is picked up by the radio via the antenna or radio wiring. The first thing you want to do is take 14-gauge wire and run the radio’s power leads to a separate battery on the shop floor. Start the vehicle and see if the radio noise is still there. If it is, it sure isn’t coming through the vehicle’s wiring, and it isn’t a bad diode. No amount of filters will help. You need to start separating anything to do with the radio from anything to do with the alternator. Building a shield may be an option. If you did the separate battery test and the noise went away, you may want to consider external filters or the possibility of a bad diode. Keep a good set of jumper cables handy. Suspect wiring can cause low alternator output, repeated regulator failures, slow cranking, low batteries and a multitude of other problems. Try going from the positive and negative connections on the alternator directly to the positive and negative post on the battery. If you see a definite improvement in operation you know the wiring has an affect. Now remove the positive and negative connections one at a time to further narrow down the problem. The same test can be done on the starter system as a quick way to identify suspect wiring. This is but a small sampling of troubleshooting tips I’ve used in the past. What was my favorite tech service call? The time the guy called to say that every time he started the engine he boiled the brake fluid out of the master cylinder. The answer? That would be Number 53—“Broken ground strap on engine resulting in starter seeking ground through brake lines resulting in bo