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Ignition fuses keep blowing and fuses are grounded

Tiny
LETHARUSSELL
  • MEMBER
  • 2002 PONTIAC GRAND PRIX
  • 3.1L
  • 6 CYL
  • 2WD
  • AUTOMATIC
  • 180,000 MILES
Every time I go to put the ignition fuse in it blows it. I also have a few fuses under the hood and next to the glove box that are showing they have negative current with the tester.
Wednesday, February 16th, 2022 AT 2:29 PM

11 Replies

Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 108,179 POSTS
Hi,

We have to have a short. Tell me, which ignition fuse are you having issues with? Take a look below, there are several labeled as ign.

Also, let me know which fuses are showing the polarity reversed. One last thing. Remove the fuse that is failing. One side of the connector in the box will have power and the other shouldn't. What I need you to do is determine which side has power. Then check the opposite side for continuity to ground. If you have continuity, we have a dead short at some point.

Let me know.

Joe

See pic below.
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Wednesday, February 16th, 2022 AT 7:26 PM
Tiny
LETHARUSSELL
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Below is the fuses grounding.
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Thursday, February 17th, 2022 AT 6:42 PM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 108,179 POSTS
Hi,

I looked through the list and it is extensive. I'm not familiar with your tester. If the light comes on and the beep. What do they indicate?

Also, the reverse voltage simply could mean you have the wires on your voltmeter reversed allowing power to flow in a different direction.

Now, I noticed you highlighted the AC diode. I need you to check for continuity through the diode. It should only have continuity in one direction. If it, has it in both directions, it is bad. It is to allow power to flow in one direction only.

Let me know what you find.

Joe
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Friday, February 18th, 2022 AT 1:25 PM
Tiny
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So, if the AC diode is bad then would that be making my ignition fuse blow?
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Friday, February 18th, 2022 AT 2:18 PM
Tiny
LETHARUSSELL
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And I hooked up a code reader but it's saying that no link is that because I have no good ignition fuse.
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Friday, February 18th, 2022 AT 2:21 PM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 108,179 POSTS
Hi,

If the diode is allowing power in both directions, it can cause all kinds of issues. Actually, that may be the reason for the "negative current" readings you found. Simply, the power flow is reversed causing the polarity to be changed.

Let me know if you get a chance to check it.

Joe
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Friday, February 18th, 2022 AT 3:48 PM
Tiny
LETHARUSSELL
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Okay. So, when I put the light tester on the negative battery terminal nothing happens in either side of the fuse spot when I put it on the positive terminal at lights up on the right-hand side and on the left-hand side it lights up and clicks down towards the starter.
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Friday, February 18th, 2022 AT 5:09 PM
Tiny
LETHARUSSELL
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And even after I remove the fuse my ignition fuse is still grounding.
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Friday, February 18th, 2022 AT 5:11 PM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 108,179 POSTS
Okay, since it fails right away, it is between the fuse and the ignition switch. It could be the ignition switch. See the pics below.

Disconnect the negative battery terminal and then disconnect the connectors at the ignition switch. See pic 4.

Once disconnected, reattach the battery and install the fuse. Does it still fail? If not, it's likely the switch itself.

Let me know.
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Friday, February 18th, 2022 AT 8:25 PM
Tiny
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So how do you unhook the wiring? I can't find a way to undo the clip.
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Saturday, February 19th, 2022 AT 1:37 PM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
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It should have a traditional connector that clips. Take a look at the pic below. I believe that is what you should have. I circled where it should clip into the switch.

Let me know if this helps.

Joe

See pic.
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Saturday, February 19th, 2022 AT 2:10 PM

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