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Old 06-20-2003, 07:29 PM
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Electrical Short, Possible Voltage Regulator

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 an external voltage regulator. 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 under the dash and that gets blown. 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 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 didnít elaborate only telling me how much it would cost to research the problem at $75.00 per hour. 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 doesnít 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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Old 06-21-2003, 12:13 AM
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Sounds to me like SOMETHING is wired wrong!

The question to answer is, "What is blowing the fuse?"

You can bench test forever, and with the unit wired properly on the bench, of course, everything checks okay.

Your wires and all look fine because the fuse keeps saving them for you.

Check ALL your wiring.

Alan
54 Chevy Pickup
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Old 06-21-2003, 01:13 AM
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I would find it hard to believe the starter is at fault. Its out of the system unless its engaged.
Motorola charging systems are difficult and expensive to repair and maintian. Personally, I would junk the alt in favor af a 1 or 3 wire internally regulated GM alt. Lots of info in the knowledge base about that. I put a 77 chev PU alt in my commando and got rid of the Motorola and its soooooo much better.
If its currently blowing fuses, it should be fairly easy to find. Remove the fuse and install a test light in place of the fuse, then start disconnecting stuff until the light goes out. Do a wiggle test of all the wires and see if you can get the light to get very bright. The light will already be on, but when the short developes, it will get real bright. Intermittant shorts are not the easiest things to fix.
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