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Pioneer head unit is dead unit :( Fuse location?

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PeriSoft

New CEG'er
Joined
Aug 26, 2006
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I've got a Pioneer DEH P7800MP which ceased operations when my alternator threw 24 volts into the electrical system. I've checked the car's fuses, and the radio fuse didn't blow.

Supposedly this HU has a fuse on the chassis, but having taken a look in there I can't find anything. What are the odds that the fuse protected it, and where can I find it?

I'm extremely sad. That thing was awesome... :(
 
Nope, nothing there. Just the connectors and a big heat sink. I found the fuse in the wiring harness (was hung up on something in there before, so I couldn't get to it), but... not blown.

I'm going to put the thing on a +12 bench supply when I can get a chance - maybe for some reason the supply isn't getting to it, despite none of the fuses being blown. Fat lot of good they did... radio fuse and harness fuse all survived and the head unit seems to have died! Good thing the Pioneer was there to protect the fuses... :P
 
If you have a volt meter check to make sure current is getting to the radio. I'm not sure if your radio has a choke (noise isolator) in the harness. Its a little black box that is mounted on the +12v yellow wire on your wiring harness that comes from the battery. It could be possible that it got fried. Check the current at your harness where it plugs into your radio, if your not reading 12v, then try where your harness is wired or plugged into the factory wiring. If you have current there then you fried the choke.
 
CarpePoon said:
If you have a volt meter check to make sure current is getting to the radio. I'm not sure if your radio has a choke (noise isolator) in the harness. Its a little black box that is mounted on the +12v yellow wire on your wiring harness that comes from the battery. It could be possible that it got fried. Check the current at your harness where it plugs into your radio, if your not reading 12v, then try where your harness is wired or plugged into the factory wiring. If you have current there then you fried the choke.
Click to expand...

There's something -like- that - but it's got a little tag on it that says 'battery' for some reason. Looks like a little transformer in there, and nothing was obviously fried. But I'll check that. Thanks!
 
PeriSoft said:
There's something -like- that - but it's got a little tag on it that says 'battery' for some reason. Looks like a little transformer in there, and nothing was obviously fried. But I'll check that. Thanks!
Click to expand...

It says Battery because that wire goes to a 12v battery source. Inside the box you probably saw something similar to this:
http://en.wikipedia.org/wiki/Choke_%28electronics%29
I dont know if it could be damaged or not, Its not very often you hear about a voltage spike going through a car. but other than your fuses, this is one of the few things in the way of getting your radio power. Might as well check it for process of elimination.
 
Well, the problem is solved.

I checked the +12, and it was fine. But...

When everything went nuts before, the spike took out the megafuse, the elec mirror fuse, and the interior lighting fuse.

I hadn't ever gotten around to replacing the mirror and lighting fuses. It had vaguely occurred to me that maybe for some reason the interior lighting fuse would kill power to the radio, but that didn't make any sense, and hey - I'd just seen +12 there, and the radio fuse was fine.

Anyway, since I was screwing around in there anyway, I decided to replace those fuses. On a whim, I figured I'd try hooking the radio back up.

Popped to life instantly.

So, apparently my particular HU will refuse to start unless the interior lights work.

On one hand, I'm upset with myself for not tracking this down sooner - it's been quite a while - and not being thorough because I got disspirited and said, 'screw it'. On the other hand, I'm f*cking ecstatic because my HU is just fine! Now I just need to find an excuse to drive somewhere... :D
 
It sounds like I am having a similar problem with mine.

before i hooked up my new HU I had tested it with only the power wires and the darn thing wouldn't power up! So i thought the HU was dead, I popped open the hood and connected them to the battery to see if it would power up, it did not.. until I held the power constant, and power accesory wires together on the positive side of the battery, and then ground to negative.
So i wired it up like that and now every time I turn the car off, all of my settings return to default.

Does this sound like a fuse that supplies the constant power or just bad wiring?
 
i know this is old thread, but i'm adding just for benefit of future searchers...
it's not PeriSoft's particular head unit that is picky about the lamp fuse (#34). without the interior lamp/electric mirrors fuse, the main power supply (orange/black wire) to the stereo does not have any power.
 
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