[EMAIL PROTECTED] wrote: > John Christensen wrote: > >> I would like to explain a bit more. My friends boat is old and the wires >> are a mess, coiled up all over the place. He inherited a partly finished >> > boat with a defective alternator. > > > >> 1. Between the keyed switch and the start push button (located on either >> side of the cockpit, there are 2 cut off raw wires sticking out as well as >> a wire for the fuel pump. When he turns the key these wires come live. >> What could they be for? Does it hurt the alternator to be left on after >> > the engine is stopped, before he turns the key off? > > > REPLY > Rather than second guessing what the original owner might or might not > have intended, you are likely better of to start fresh. If the wiring is > in good shape, and run from the required point to point; you can reuse > them. Follow the factory recommended wiring schematic and ignore the > quirks and foibles introduced by the previous owner. Maybe the cut-off > wires were used for an hour meter or maybe it was for an added instrument > now removed; or maybe . . . . (who cares) > > Use the factory schematic as your guide. > > As to hurting the alternator; not not exactly. However; I was once > called in to solve a major corrosion problem for a big yacht dealer with > five million dollar boats for sale, all of them exhibiting corrosion > problems while at the sales dock and before they were ever sold. I traced > the stray current to the alternators which were permanently energized. > Because the engines were stopped, the regulator full-fielded the > alternator and the stray current dumped into the seawater via the prop > shaft. Someone had forgotten to wire the Alternator through either a key > switch or an oil pressure switch in the factory assembly drawings. Thus > they were always energized. Not so much of a problem if plugged into > shore power, but would quickly flatten a battery if boat was anchored out. > > regards > Arild > > > > __ I agree with Arild. Use the factory schematic. I was surfing the web wrt alternators the other day and came across an article describing how to wire a 10SI Delco alternator. It was patently incorrect, so if you are using the web as a resource be sure to get more than one opinion.
Here's a typical alternator hookup. You will have up to 5 connections. Ground. Most alternators have a terminal on the case that should go to ground. Don't rely on the mounting bolts to provide ground. They sometimes don't. It's been my experience that faulty grounds are one of the most troublesome problems, because people tend to overlook the ground connections. This is true in cars, motorcycles, boats and electronic, not to mention house wiring. Output. This terminal can usually be identified by being the one with the biggest wire connected to it. It is often an insulated stud connection not associated with any other wires. It is highly recommended that this wire run directly to the battery or to another connection that is tightly connected to the battery, such as the hot side of the starter. Many installations have a large wire directly from the battery to the starter and I've seen the Output from the alternator go to this post also. That's a good place to connect it if you have the starter circuit running through a battery disconnect switch. (Which I don't recommend for larger engines). Field. This is the wire that must go to a switched ignition. It provides the exciting current to the alternator field circuit and will draw current so it must be disconnected when the engine is not running. It is highly recommended that this switched ignition be of the type that is disconnected when the starter is engaged. On common automotive switches there will be two switched ignition terminals, one will be hot any time the switch is on, and the other will be hot only when the switch is on and the starter is not engaged. On smaller engines the load placed on the alternator can be large enough to prevent the engine from starting easily. I've not experienced this but I'm told that it can be a problem. If the ignition switch does not have the capability of providing the disconnect on start, then I wouldn't worry about that problem unless the engine is hard to start and acts like it's not spinning fast enough. Sense. This is a very important wire. This is the feed back to the regulator that tells the alternator "that's enough". It needs to be connected to the battery. How or where it connects depends a lot on your installation. Some solutions suggest that you run it to the Output terminal of the alternator. That is probably the safest connection. If this wire becomes disconnected or is connected to a location that differs greatly in voltage from the Output terminal, you can destroy the diodes in the alternator. It usually happens when someone ties this wire to a battery that is separated from the charging circuit by a battery switch and forgets to close the switch. A disadvantage of having the Sense tied directly to the Output is that there is resistance in the wires between Output and the battery being charged. At high currents (lots of batteries, and/or depleted charge) this will result in a lower voltage at the battery which in turn will necessitate running the engine longer to get a satisfactory charge. Running the Sense wire directly to a battery that is always connected to the Output terminal but AT the battery or close (electrically) will result in getting full voltage to the battery. By "electrically close" I mean connected to a point that has a very low resistance path to the battery. For example a 3 foot run of 2/0 cable from the starter to the battery. I would suggest that running the Sense line to the same point the Output line is connected to is a reasonable procedure. The last wire you may have on an alternator is the output for the Tachometer. I'm not suggesting that this is a complete document on how to connect alternators, it's just one way to do it. The important things are, switch the Field wire off when the engine isn't running. Be sure the Sense wire is always connected somehow to the Output anytime the engine is running (not necessarily directly, but it has to be at the same approximate voltage for efficiency). And don't forget to ground the alternator securely. Let the flames begin! ;) Jim. _______________________________________________ Liveaboard mailing list [email protected] To adjust your membership settings over the web http://www.liveaboardnow.org/mailman/listinfo/liveaboard To subscribe send an email to [EMAIL PROTECTED] To unsubscribe send an email to [EMAIL PROTECTED] The archives are at http://www.liveaboardnow.org/pipermail/liveaboard/ To search the archives http://www.mail-archive.com/[email protected] The Mailman Users Guide can be found here http://www.gnu.org/software/mailman/mailman-member/index.html
