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Old 12-08-2008, 03:02 PM   #1
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Default keep blowing primary battery fuse 20amp

Okay, near the passenger side of truck 97 f1504x4 there is a primary battery fuse that connects between wire on alt and primary fuse block, this fuse blows soon as I install one in the vehicle running or not, has anyone ran into this problem could it be a bad alt? I traced all possible wires and none seem to be grounding out any place and all grounds seem to be making a good ground connection, the truck has a new battery and starter installed prox three months ago, the truck does run and start but with out this fuse in place it will not charge and it runs on battery til it is dead then stops running completely, I traced batery wires, alt wires, starter wires etc, and all lights inside and out seem to be working fine, radio etc all working fine, as well as all power options. do you think maybe something inside the alt is messing it up? thanks for any tips or advice ahead of time!

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Old 12-08-2008, 05:50 PM   #2
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Yes, power goes to alternators "A" terminal at all times. Take an ohm meter and with alternator disconnected measure the resistance. Your has to be shorted. If an ohm meter is not available, remove alternator and have it tested. Something is wrong inside.
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Old 12-09-2008, 10:40 AM   #3
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Default problem fixed

Hey thanks for the help, it ended up being a bad diode in the alt, took it off had it tested guy thinks maybe someone reversed polarity durring a jump, probably stupid me, anyhow got a new alt installed and problem fixed... Thanks for the assist and info
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Old 07-17-2012, 06:11 PM   #4
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hi im haveing a simular problum but not the same i just had some new spark plugs put on and at that time we lost a tool down in side the engine so we had to remove the alt. and primary fuse box looking for the lost tool im afraid tha maby we didnt hook up the primary fuse box back up corectly because the to red power wires go to one bolt on the right side and the bolt next to it has nothing on it i downloaded the user manul both the power network box mega fuse and alt. mega fuse have red wire sticking out the left side goingto the same bolt and im not sure if that right im thinking the alt. mega fuse red wire might need to go on the bolt on the left insted but not sure

i have just installed new spark plugs and new battery at first i tryed to turn it over and nothing but then after letting it charge for a wile i get a click when turning the key it sounds like the click comes from the primary fuse box

My truck wont start i cant figure out whats wrong its driveing me nuts can anyone help?

A picture of the wireing for the primary fuse box would help.
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Old 07-17-2012, 06:11 PM

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