Ignition key fuse keeps blowing

Tiny
TY KEITH
  • MEMBER
  • 2004 MAZDA RX8
  • 2WD
  • MANUAL
  • 140,000 MILES
It keeps blowing ignition key fuse as soon as I turn the key. Not even try to turn it to crank the first turn of the key will blow the fuse. I’ve pulled all the wiring out and replaced some bad wires and it worked for about 30 minutes of driving and now it’s started back blowing the ignition key fuse.
Thursday, July 16th, 2020 AT 2:24 PM

12 Replies

Tiny
ASEMASTER6371
  • MECHANIC
  • 52,796 POSTS
Good evening,

Can you tell me which fuse number is failing? I need that to see what it controls so we can get to the root cause of the failure.

https://www.2carpros.com/articles/how-to-check-a-car-fuse

Roy
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Thursday, July 16th, 2020 AT 2:54 PM
Tiny
KASEKENNY
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When you are saying it is blowing the ignition key fuse, I assume you are talking about the IG fuse? Basically the one that feeds the ignition relay? If so, this actually does not have anything to do with the key/ignition switch (most likely).

Take a look at the wiring diagram. As you can see this fuse feeds the ignition relay which ends up leading to the ignition condenser and coils. Most likely have a shorted wire but here is what I would suggest the easiest way in finding this. Go to the coils and unplug all of them and then the condenser. Turn the key back on and see if the fuse blows. If not, you have unhooked the issue. Then start plugging them back in one at a time and turn the key on and continue this until the fuse blows again. At that point, you either have a short in that component or the wiring too it.

Let me know if you have questions and we can go from there. Thanks
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Thursday, July 16th, 2020 AT 2:59 PM
Tiny
TY KEITH
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It is this one that keeps blowing ig key 15a. I’m going to try to unplug coils and condenser now.
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Thursday, July 16th, 2020 AT 3:13 PM
Tiny
ASEMASTER6371
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Okay, just to throw in my 2 cents. That wire goes to the ignition switch.

Disconnect the switch or just the yellow wire. It sends a feed out to the ignition system.

Roy
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Thursday, July 16th, 2020 AT 3:26 PM
Tiny
TY KEITH
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Unplugged coils and condenser and it still blows the fuse when I turn the key over. I’m going to try the ignition switch now. But how will I know if it blows if I can’t turn the key over without the switch plugged in.
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Thursday, July 16th, 2020 AT 3:30 PM
Tiny
TY KEITH
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I unplugged the switch with key turned on and it didn’t blow, but as soon as I plugged it back in it blew.
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Thursday, July 16th, 2020 AT 3:40 PM
Tiny
ASEMASTER6371
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See if you can pull the yellow wire out of the connector.

Then plug the connector back.

My thought is either wiring to the ignition switch or a possible switch.

Roy
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Thursday, July 16th, 2020 AT 3:42 PM
Tiny
TY KEITH
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I unplugged the yellow wire and it did not blow, but I replaced that whole wire yesterday because it was melted it worked for about 30 minutes then started popping fuses again.
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Thursday, July 16th, 2020 AT 3:46 PM
Tiny
TY KEITH
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Does the starter get any power on the first key turn?
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Thursday, July 16th, 2020 AT 3:50 PM
Tiny
ASEMASTER6371
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No, it does not.

How far back did you replace the wire?

If it melted there, I would replace the switch as well.

Roy

IGNITION SWITCH REMOVAL/INSTALLATION

1. Disconnect the negative battery cable.
2. Remove the column cover.

ImageOpen In New TabZoom/Print

image

3. Remove in the order indicated in the table.
4. Install in the reverse order of removal.
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Thursday, July 16th, 2020 AT 4:08 PM
Tiny
TY KEITH
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So I ran a wire from the battery straight to were the yellow wire would be and it works.
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Thursday, July 16th, 2020 AT 4:20 PM
Tiny
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Then you have a wiring issue between the fuse box and the ignition switch. You need to open the harness and inspect it for damage.

Roy
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Thursday, July 16th, 2020 AT 4:22 PM

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