If you have a 30 amp car fuse that keeps blowing , how do you test without blowing a ton of fuses? Are there any guides for techniques for finding shorts?
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1991 240sx
alarm=model 2620.web central door locking system
Grind the plastic off of one of the already blown fuses and solder a 12 volt light bulb across the 2 terminals of the blown fuse. Use enough wire to reach the area that you think the short is in. Or use a 12 volt buzzer. With a bulb you do not need to check for polarity. If you use the buzzer you may have to figure out which terminal of the fuse is hot and which is ground. As long as the short is present the bulb will burn brightly or the buzzer will buzz loudly.
Thanks for the fast response. I appreciate it.:) So the bulb will eat all the amps so that nothing gets damaged in the rest of the circuit, I assume. I have not studied this in years. Thanks again.
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1991 240sx
alarm=model 2620.web central door locking system
the bulb will act as a load & not a dead short, so it makes it safe.
Good stuff:) been trying to get an answer about this for years. thanks.
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1991 240sx
alarm=model 2620.web central door locking system
A 3o amp circuit breaker as used in the aircraft industry would also do the job.
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Not Fade Away
The easiest road is usually the last one sought
With nothing to limit the current, the 30 amp breaker will constantly be tripping and resetting itself. Hope you can find the short before the battery goes dead.
If you have a direct short that is immediately blowing a 30A fuse you can just use an ohm meter between the output of the fuse and ground. If the fuse takes a while to pop or only pops while you are driving that would require a resettable circuit breaker.
The method I would use to "quickly" locate the spot of the short would vary greatly depending on what kind of circuit it was. If it was a 30A power wire for an amp I would go about it completely different then if it was a 30A OEM lighting circuit. If you provide us with more information maybe we can offer better solutions.
With that being said, I have found it easiest to divide and conquer - the smaller the area you can isolate the short to the easier you will be able to find it and fix it.
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Kevin Pierson
The 30 amp fuse supplies power to the ignition switch. When the key is turned to the on position , the fuse blows. The fuse also blows sometimes when car is driving. Power goes from battery to 30 amp fuse and then to ignition switch. ignition switch has an accessory position , the on postion and then the start position. Thanks for the help.
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1991 240sx
alarm=model 2620.web central door locking system