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Bruce is Owner and Senior Mechanic of Southeast Marine Services, Inc. in the Palm Beach, Florida area. His extensive background, in Marine Mechanical Systems, encompasses both gasoline and diesel engines, air conditioning, and electrical and hydraulic systems.
"Bruce is one of the most 'In Demand' Systems Technicians we have in our area. His expertise is exceptional!"
(Capt Patrick McCrary, webmaster)
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The Mysteries of Electrical Systems
September 27, 1998 I thought for this next article that we would get away from machinery and focus in on some common electrical problems and how to solve them. Electrical systems are not as complicated as they are made out to be. They only become complicated after the amateur electrician has his hand at rewiring. There are a few rules to follow, don't take a bath with a plugged hair dryer and don't lean over a battery with a dangling jewelry chain and touch ground. The red ring around your neck will explain why. Electrical systems need a completed path to work. On DC, or direct current systems, the current goes out from the negative source, through a load (light, etc.) and back to the positive, through the battery, and back to the negative thus completing a path. The electrical molecules travel in one direction hence the name direct current. AC or alternating current has the molecules traveling back and forth on the same wire. On 110v systems the black wire is hot, the white is neutral and the green is ground. On 220v systems the black and red are hot, each wire has 110v on it, together they produce 220v, and the green is ground for safety. Unless there is a 110v load with the 220, there will be no neutral. The reason people get a shock is because their body acts as a bridge to complete the electrical path. If you had well insulated shoes on a dry day, you could grab the hot wire of a 110v circuit without touching anything else and not get a shock. (PLEASE DON'T TRY THIS TO SEE IF I'M RIGHT, I AM. THIS IS NOT MR. WIZARD'S SCIENCE CLASS.) I've heard some people say that you can't get shocked by DC, WRONG! It just takes higher voltage. Most welders are DC and if you ever pulled a spark plug wire off a running engine you know what I mean, about 30,000 vdc. This is a basic and simple explanation of these systems. On to some common problems, first DC.1. My lights won't come on. assuming the batteries, switch and the bulb is good a common problem I find is a bad connection. You can have good voltage at the switch with the switch off, but when you turn the switch on, the voltage goes away. This is a sign of a bad connection. What happens is there is a good enough path to get a reading on a voltmeter because there is no current draw, but as soon as you try to draw current, the connection won't handle it and the path opens up, thus an open circuit. An easy way to find which side, plus or neg. is bad is to put each voltmeter probe on a different feed one at a time and see which one allows the voltage to remain constant. This will work for any DC problem of this nature. 2. My solenoid clicks but nothing works. Most solenoids have four connections, The two small ones are for the coil and the two large ones are for the switched load. The coil is a basic Electro-magnet. When you apply voltage to these terminals it pulls down a metal plunger inside with a bar or washer that makes contact with the two heavier terminals, connecting them and completing a path. That's the clicking sound you hear. The common problem is that the internal connecting bar or washer can become burned or corroded from the load and after a while it won't connect the two heavy terminals together. A good way to check is one large terminal will be the feed and the other the load. Place the black lead of a voltmeter to ground and the red to the feed, if you have voltage, energize the solenoid and check the load side, if there is no voltage then the solenoid is bad even though it clicks. 3. My dash gauges jump around. Sometimes a faulty sender can cause this, but most of the time there is a bad ground. A good ground is just as important as a good plus. A good way to check is to run a #10 wire from the ground on your battery to the ground on the gauges. If the gauges stop, repair the ground feed. Some AC problems.1. I get a reverse polarity indication. The ground or neutral wire becoming the hot leg causes this. Most of the time it is caused from bad dock wiring or a shore cord wired wrong. There are markings on all dock cord connectors to make it easy to replace them and wire them correct. This can be a dangerous situation as it can put a hot voltage on the ground connections that you normally touch, leading to a shock. It can also cause severe electrolysis and lead to thru-hull fittings being eaten away. 2. My shore cord ends burn, melt and I lose power. This is caused by a poor connection, either from moisture or worn connectors. Pulling the shore cord in and out will wear it out eventually. These should be checked every six months. When they start to get loose, replace them. Yes I know it is expensive, but it is better than trying to get rid of that rotten bait smell out of your freezer and trying to explain to your wife why you left it in there in the first place. 3. My voltage is low. Again, a bad connection usually. Check all connections from the dock to the back of your electrical panel. These are just some common problems. Please, if you don't feel comfortable working on electrical systems then don't. You can use this information to help diagnose the problem for a technician or to understand what they tell you. Remember, electricity can kill, so don't play around with it. If you have any questions you would like to ask, please visit the forum section. It's a great source of information. SMOOTH RUNNING, Bruce |
Mechanical Feature Articles Mechanical Equipment Reviews Mechanical Service
mechanical section / Saturday, February 21, 1998
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