Electrical Short, Possible Voltage Regulator? Help!

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Claude [guest] from 10W40.com
Electrical Short, Possible Voltage Regulator? Help! Posted 6-29-2003 04:16

I have a ski boat with a 455 Olds engine. The engine has 283 hours and has been garaged since it was purchased. The alternator (original) is a Motorola with the voltage regulator attached to the backside. Here is my problem...when accelerating and maintaining a decent speed other than an idle the gauges will start to bounce back and forth. At this time the engine goes dead. There is only one fuse 15 amp under the dash and that gets blown. This fuse is attached to the battery side of the ignition switch, splits off to the bilge pump switch then goes to the amp gauge. Once I replace the fuse the engine fires up and continues on. A little while later the same set of circumstances, blown fuse. I went to my local boat repair shop and they made several recommendations. I replaced the ignition switch, the coil and ballast. This did not cure the problem. I looked under the dash and have a clear view of all wires. None were touching the other, no bare wires whatsoever. All wires going to the engine are in good condition no breaks in the insulation either. I wiggled all of the wires and no short. I took the alternator off and had it bench tested. The first place could only test the alternator not the voltage regulator. He said the alternator was fine. I went to the second place he bench tested the alternator and voltage regulator and said both components work fine. I replaced the amp meter and then took the boat out and had no problem. Several hours later the problem came back. I replaced the fuse and turned the ignition key on and the fuse would blow before the engine would start. Replaced the fuse and it got blown again. This happened several times and I had to be towed in. I went back to the boat repair shop and another mechanic told me it was the starter that was shorting out. He didn't elaborate only telling me how much it would cost to research the problem. The starter works fine no indication of going bad whatsoever. I have been told that even though taking the alternator off of a boat and/or car and having it bench tested doesn't necessarily find the problem. I am wondering if the voltage regulator is intermittently going bad. Any input would be greatly appreciated. Thank you.
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chevyguy [guest] from 10W40.com
electrical problems Posted 6-29-2003 12:41


i would try disconnecting the bilge pump it might be bad or just taking to much of a draw on the fuse.
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Harvester [guest] from 10W40.com
Electrical trouble Posted 7-1-2003 16:33

The bilge pump suggestion is a good place to start, but also disconnect any accessories, lights and the like, one at a time to see if one those circuits causes the fuse to blow. It is pretty safe to say the starter is not the cause of your trouble, but make sure the battery connections are clean and tight. I assume your boat has a fiber glass hull, so the electrical system needs a good ground circuit, probably the engine is the common ground point. Make sure all the ground connections are clean and tight, including the battery negative cable connection on the engine, or at the ground buss if the boat has one (its probably the engine). The voltage regulator needs the battery negative for a reference. If the reference fluctuates because of a loose or corroded connection, the voltage also fluctuates accordingly, usually increasing rather than decreasing. That might account for the instrument fluctuation you notice before the fuse blows. I would also assume that the alternator and voltage regulator are satisfactory, at least at this point. The battery itself is not above suspicion, and you could have it tested, but I would look into the ground circuit and connections first. Hope this helps, let us know how it goes.