BAT reading 1.1v, ACC reading 12v

[CrazyNorman]

I'm pretty sure I know what caused this problem, but I have no idea how to approach fixing it. This winter, I went out one day, and my battery was dead. A helpful neighbor came out, and offered to jump my car. Long story short, I look away for a second, I look back, he has the cables cross-wired Pos to neg, with a little bit of smoke coming out!

Luckily my battery was so dead that nothing caught fire, and after connecting the cables correctly I was able to jump my car and be on my way. Only damage I've noticed is that the radio no longer works. The car drives fine, cruise control/dash work, etc, just no clock/radio. I checked the fuse and it was fine.

Fast forward to today, I decided to replace my (assumedly) broken radio. I wired up a harness, plugged in the radio, and nothing, no power. I worked off of this manual: http://www.nicoclub.com/FSM/Sentra/2010/AV.pdf for my 2010 Nissan Sentra. I did some debugging with a volt-meter, and what I found is that while ACC (page 14 pin 7) reads a normal 12v with the key set to ACC, BAT (page 14 pin 19) only reads ~1.1-1.2v. I'm thinking this is why the radio won't power on. I checked the harness I built and the resistance is low on both connections, but with BAT reading only 10% of the expected voltage.

Any ideas or suggestions?

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[dubstepper1000]

I'm pretty sure I know what caused this problem, but I have no idea how to approach fixing it. This winter, I went out one day, and my battery was dead. A helpful neighbor came out, and offered to jump my car. Long story short, I look away for a second, I look back, he has the cables cross-wired Pos to neg, with a little bit of smoke coming out!
Luckily my battery was so dead that nothing caught fire, and after connecting the cables correctly I was able to jump my car and be on my way. Only damage I've noticed is that the radio no longer works. The car drives fine, cruise control/dash work, etc, just no clock/radio. I checked the fuse and it was fine.

Fast forward to today, I decided to replace my (assumedly) broken radio. I wired up a harness, plugged in the radio, and nothing, no power. I worked off of this manual: http://www.nicoclub.com/FSM/Sentra/2010/AV.pdf for my 2010 Nissan Sentra. I did some debugging with a volt-meter, and what I found is that while ACC (page 14 pin 7) reads a normal 12v with the key set to ACC, BAT (page 14 pin 19) only reads ~1.1-1.2v. I'm thinking this is why the radio won't power on. I checked the harness I built and the resistance is low on both connections, but with BAT reading only 10% of the expected voltage.

Any ideas or suggestions?

Check your voltage under the hood, if it is normal, you fried the wire between them. otherwise, buy a new battery

 

[CrazyNorman]

That makes sense. I assume the battery can't be too messed up given it starts the car, but I'll check it again.

Silly question, but how does one "fry" a wire? I could see too much current melting a connection, or a mechanical force snapping it, but I didn't even blow a fuse. I'm assuming it is a fried wire, it makes a lot of sense that it would cause the problem, but I'm trying to understand how it could happen, even with a reversed jump //content.invisioncic.com/y282845/emoticons/confused.gif.e820e0216602db4765798ac39d28caa9.gif

 

[wew lad 5,000+ posts]

increasing the resistance substantially in a wire due to exceeding its thermal capability is what you could call "frying" a wire. it can be so bad that the casing melts and the wire separates, or it could be so small that the wire melts in one spot causing so much resistance that no current gets though

If you want a good example look at fuseable links. make sure to check your fuse box too, might of blown a fuse there. keep in mind just because a fuse doesnt look blown, doesnt mean it isnt, replace it with a known good fuse to check.

 

[dubstepper1000]

mitchell is right, if you are looking for an easy quick fix, using the ACC as your constant power and your ACC power cord will allow the radio to work, but every time you turn off the car, all your settings on the radio will be reset to factory, but if all you have changed is the time, shouldn't be that big of deal. Otherwise, your are going to have to run a new wire to the dash from the battery