# Acc wire no voltage



## r0bb1e

Okay so I was wiring my first radio, and I decided I'd go hell for leather on it. Me and an electrician buddy set up a Pioneer head unit (SPH-DA120) amp and sound system (Pioneer GM-D8604). All good.

Then I added a reverse camera, which I took power off the acc wire (I new realise I shouldn't have) and ran a steering wheel control interface's main power off the acc wire too.

So the whole system is working v. Well, but I take a break about an hour into the journey to get food etc. And when I get back into the car radio screen black, no amp power. 

To make a long story short I get a multimeter and check every fuse I can see - All good. Ground and constant 12v good. All connectors removed and reconnected. V frustrating. Anyway eventually I realise the switched 12v wire has 0 voltage when on and off. If I put the keys in acc position I can still move windows etc but no voltage. It's an Opel Corsa (A 1.3l diesel which is very bare bones)

Any idea would be greatly appreciated. It's driving me insane!!


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## FlyingEagle

Does the whole car operate properly, starting, engine running, etc?

Check the wire that you tapped into for accessory power, and if it does not show voltage when the key is turned forward, then you are looking further up the ignition switch (which if enough is piggybacked across that) you can burn the contacts. Basically follow that original wire you tapped into until you get back to a fuse in the interior fuse panel, or until you a point where power is back on the wire, and indicating a bad section. You could have popped a fuse.

I would go back and double check all items that are wired to power and ground.


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## r0bb1e

Yes that's almost more annoying. The whole car works like a charm - Electric windows, cigarette lighter. Everything's perfect except the stubborn black screen on my radio and then the amp as a result.

Thanks for the advice though I think if I follow the wire back I should (hopefully) find something!! There might be an inline fuse or something?


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## FlyingEagle

The radio likely has a little black plastic case or an inline fuse holder with a pull top, that allow a quick swap of the fuse inside. Why would a fuse pop ... most of the time it is an over current issue, but occasionally, a fuse falls apart or corrosion stops the contacts working properly. I recently found a baked fuse in my Kenwood amp that was previously in my project car. The amp worked fine, but the fuse was bubbled, and still intact!
If you do find a burnt fuse, be sure to check your wires and connectors for a possibility that could touch bare metal - the chassis on the radio is metal too! That will cause a fuse to pop when a dead short is introduced.


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## r0bb1e

Yeah Ive checked all the fuses I can get my hands on with the multimeter though and nothing... I got the acc wire from the factory location which was only intended for the OEM radio.

What I think could of happened was there was current for the reverse camera and stuff producing much more heat than was accounted for originally, and it was county roads so through the bumping and heat a wire could have very easily came away now that I think of it!

I'll check all the associated fuses again aswell and I might send in an update tomorrow - I have a couple hours to work on her. That being said I can't see it being a very fun job tracing the factory wire the whole way back


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## audiokid1

Back to basics....

Pull the radio and bench test it if possible. Or temporarily tie the radio's accessory input to the constant input and see what happens.

Tell Johnny Rea to slow down please....


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## Locomotive Tech

When you say accessory wire, you are speaking of the one from the car's ignition right?


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## SPLEclipse

Fuses can be strange. Replace the one on that circuit just in case.

While you're at the fuse box with the fuse pulled, use your multimeter to check continuity by probing the end of your acc wire (where it would connect to the headunit) and one of the sockets where the fuse slides in. There should be continuity on one side of the fuse. If there's no continuity in either socket where the fuse slides in, you have a broken/burned wire.


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