1G Ignition fuse blows with key off

[pitbull419]

Everytime I hook up the battery the ignition fuse blows instantly. The key is turned off. I cant find any indicators of physical damage anywhere. I did a search and most cases were when the key was turned to on or a dead end with no answer. Thanks for the help in advance

Car is bolt turbo automatic

 

[Talyn]

Sounds like the wire that feeds 12v to the ignition is grounding out.

 

[pitbull419]

That's what I'm thinking but how do i find out where if there's no obvious physical damage

 

[steve]

Disconnect the ignition switch connectors and then measure the resistance to ground from the positive terminal (battery disconnected of course)

 

[wrencher]

I'd look into the turbo timer if you have one installed also.

 

[pitbull419]

Ok here is what i did. with the ignition fuse out i tested the output side of the fuse connector post and it read 0. However i also read the side that's actually touching the battery terminal and it read 1675. I also did the same thing for the center fuse(rad fan) and the output side read one and again the other side read 1675 also.

No turbo timer car is completely stock.

 

[steve]

You need to know what does your meter read on the resistance settings when the probes are not touching and when they are? Almost every meter I've held does something different but usually with the probes not touching the display flashes something. When they are touching it should read something close to 0.

Since the fuse is blowing you have a low resistance in the circuit between the battery positive and negative terminals. In typical car the negative terminal is connected to the chassis and is called ground so your looking for a short in the power from the positive to ground.

Since you are blowing the ignition fuse you know you have a short in that circuit and since it's with the ignition switch off either the ignition switch is bad or you have a short before it.

First step was to disconnect the ignition switch and test but measuring the resistance between the positive terminal of the harness and ground. Since the fuse is still blown you shouldn't measure anything close to 0 ohms, if you do there is still a short that the fuse isn't protecting or your using too high a range on the meter. The Hundred or Thousand (1k) ohm rage is good to these tests.

Your going to need the wiring diagrams from the factory service manual. The idea is to check segments of the wiring to look for problems and shorten those segments step by step to find a problem. If the large segment isn't shorted then the smaller parts of it also aren't shorted. Move on to the next segment.

I had you start with the first large segment to verify based on your information, from the positive terminal to the ignition switch. If I understand what you measured, you measured between the terminal and the ignition fuse and between the other side of the fuse and ground. Between the positive terminal and the battery side of ignition fuse you saw 1675 somthings (need scale and position of decimal place) the other reading was 0. I assume the ignition switch was still connected.

The ignition circuit is a direct run from the ignition fuse to the switch, nothing normally can draw power from that circuit if the switch is off.

The question is, is it the switch or the wire? Disconnecting it is the next step and remeasuring from the ignition fuse to ground. If you get a high resistance it's not the wire.