Fuse with LED - JeepForum.com
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post #1 of 4 Old 04-29-2014, 08:25 PM Thread Starter
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Fuse with LED

Was in Pep Boys and saw fuses that glow when they burn out. Wouldn't that mean that there was still current flowing? Sort of defeats the purpose of a fuse.

What am I missing?

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post #2 of 4 Old 04-29-2014, 09:11 PM
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One side of the fuse is always hot even if the fuse is blown (pull a fuse out and put a volt meter on each side of the socket..one of them is hot). Not sure how the LED gets it's ground after the fuse blows but it does not affect the way the fuse protects the circuit.

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post #3 of 4 Old 04-30-2014, 06:19 AM Thread Starter
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So what I figure is, there is a resistor and LED in parallel with the fuse. When something shorts or draws too much current the fuse opens. Now the current has no choice but to run through the resistor/LED.

The LED lights up. Even if the cause of the problem was a direct short to ground, the resistor/LED drop the entire 12 volts. There is still current flow but it is minimal. Maybe 10-20 ma.
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post #4 of 4 Old 04-30-2014, 07:15 PM
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If you please a fuse one side is hot and the other side will show ground because the ground flows trough what ever is in that line. Think of it lime a series circuit. So when the fuse is good the power flows trough the fuse part and bypasses the led. When it blows the load side of the fuse turns to ground turning on the led.
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