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  12-Volt Distribution: Troubleshooting

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Author Topic:   12-Volt Distribution: Troubleshooting
1flcheesehead posted 01-18-2007 07:45 AM ET (US)   Profile for 1flcheesehead   Send Email to 1flcheesehead  
I am having problems with some instruments on my 'new' (used) boat. I have an Aqua Signal Dual Horn and a Garmin GPS that are not working. I tested both for power and they both have 12-volts. I ordered a new horn and put it in and it did not work. I also sent my GPS unit back to Garmin for repair and they said there was nothing wrong with it. I am waiting for another replacement horn and Garmin will be sending out an AC power cord for me to try. In the mean time, has anyone ever seen I situation where power is present, but for some reason things don't work? I am stumped. It has been years since I have had electrical classes and I can't seem to come up with a scenario where this could be possible. But what are the odds of a new horn being defective and Garmin mis-diagonising my GPS?? Thanks for you help!
bluewaterpirate posted 01-18-2007 10:53 AM ET (US)     Profile for bluewaterpirate  Send Email to bluewaterpirate     
Do you have an spare 12v marine battery that you have access to? If you do you can connect your GPS/horn (ensure the inline fuse is installed) to that battery & verify the GPS/ horn are working correctly.

How are you connecting your equipment to the power source (i.e. directly to the battery, thru a fuse buss. or thru a helm switch. Ensure you have a good ground source.

Tom

HAPPYJIM posted 01-18-2007 11:08 AM ET (US)     Profile for HAPPYJIM  Send Email to HAPPYJIM     
It may be a loose connection or corroded contacts. The correct voltage is present but there is not enough amperage to operate the equipment. Does the horn and GPS come off the same fuse?

Hook the horn to a different power source like a 12 volt battery charger or just touch the contacts to the battery. If it works it may be easier to rewire the circuit than try to trouble shoot a corroded conection.

Peter posted 01-18-2007 11:54 AM ET (US)     Profile for Peter  Send Email to Peter     
Yup. Your problem is corrosion somewhere in the circuit that feeds the electronic devices which is not allowing the electronic devices to get the proper current for operation. Although it appears you are getting the proper voltage with a volt meter, that is without any load. The voltmeter draws virtually no current so things will appear OK when they aren't.

What you need to do is Check for corrosion in the circuit by tracing the circuit from the electronic units back to the battery which supplies the electricity to them. I'll bet you find a corroded terminal, switch or joint somewhere in that circuit.

bms1939 posted 01-18-2007 03:08 PM ET (US)     Profile for bms1939  Send Email to bms1939     
Bad connection, bad ground, or bad wire, a very slim chance the horn and the GPS unit is bad. In the marine environment corrosion wreaks havoc on electrical connections. I had problem with my trim tabs, turns out someone punctured the wire with a test light tip and it corroded the wire inside. Sometimes the corrosion will go up the wire from the battery connection, you can replace the connector and still not get the proper amperage to your equipment. Also check the size of the wire from the battery it might be too small to run your equipment. Depending on the age and condition of your boats electrical system you might want to upgrade it, its very easy to do. There is nothing worse than every time you head out to have to start wiggling wire connection because your depth finder, lights, etc. are not working. I did my twin engine 4 battery system without too much trouble at all, just a little sweat, a few cuts and a curse or two.
1flcheesehead posted 01-18-2007 04:17 PM ET (US)     Profile for 1flcheesehead  Send Email to 1flcheesehead     
Thanks for all your suggestions. I will look at the wiring tonight. hopefully the GPS was grounded with the Horn at the fuse block and that is where the corrosion is.
davej14 posted 01-18-2007 04:57 PM ET (US)     Profile for davej14  Send Email to davej14     
Have someone actuate the horn with the voltmeter attached and see how the voltage fluctuates. If you have a good connection to the horn and switch it will drop significantly indicating the corrosion is at the battery, ground or fuse block.
1flcheesehead posted 01-19-2007 07:30 AM ET (US)     Profile for 1flcheesehead  Send Email to 1flcheesehead     
Right on. I fiddled and poked and prodded. Ultimately I discovered the Fuse Block itself was corroded INSIDE. There was no outward appearance whatsoever. When I removed the GPS power lead from the fuse block and plugged it into a known function slot (navigation light) it worked. I bought a new Fuse Block last night. Will install it tonight if it stays light outside long enough. Thanks for the tips!
BW23 posted 01-19-2007 04:37 PM ET (US)     Profile for BW23  Send Email to BW23     
While your at it, spray all of the fuse terminals with a product like CRC 226 or Corrosion X.

This will help prevent new corrosion.

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