fault finding on Pioneer DEH-P6900IB head unit

[cantfindausername]

Hi all,

I've somehow (stupidly) managed to fry 2 (yes 2!!!) head units when fitting them in my car.

I'd done a bit of re-wiring and thought I understood what was going to happen, but I got some very unexpected results.

I was fitting a new 12 way power distribution block to give me 6 feeds on a constant feed from the battery, and 6 feeds on an ignition controlled relay (IGN powered supplies). The distribution block has a shared earth which I'd ran directly back to the battery -ve.

The car also has an Isolation switch fitted in the cabin which cuts the main battery/chassis earth cable.

I figured I'd run 1 Ign. and 1 Const. to the head unit along with an earth feed. This in my eyes would give a constant power for the internal battery of the head unit, and also the switched power of the Ign circuit.

When I started to install the head unit though the case started to spark whenever it touched anthing attached to the chassis, even though the Isolation switch was off. It seemed like the case of the headunit case becoming postively charged.

As such I've got 2 dead head units that I'm really cheesed off about.

I'd like to have a go at fixing them if possible but I don't have a clue where to start.

I'm also really confused as to what has happened here. If I could get the head units working I'd happily just run them off the Ign and deal with having no memory as this is how it used to be.

I just wants music back in my car - I really hope someone can offer me some assistance!

Many thanks in advance,
Anthony

 

[cowana]

Sounds like you got the + and 0v lines round the wrong way on the head unit.

Is there a fuse inside?

 

[cantfindausername]

Thats what I thought, but there was no way I would have. Was using clearly different colour cables, and when away from the mounting position the stereo worked fine, it was when I went to put it in place that it caught a metal part of the dash and sparked.

I've just pulled one of the head units apart and there is no fuse inside the unit. Only on the outside and that hasn't blown.

 

[Mickster]

Hi all,

I've somehow (stupidly) managed to fry 2 (yes 2!!!) head units when fitting them in my car.

I'd done a bit of re-wiring and thought I understood what was going to happen, but I got some very unexpected results.

I was fitting a new 12 way power distribution block to give me 6 feeds on a constant feed from the battery, and 6 feeds on an ignition controlled relay (IGN powered supplies). The distribution block has a shared earth which I'd ran directly back to the battery -ve.

The car also has an Isolation switch fitted in the cabin which cuts the main battery/chassis earth cable.

I figured I'd run 1 Ign. and 1 Const. to the head unit along with an earth feed. This in my eyes would give a constant power for the internal battery of the head unit, and also the switched power of the Ign circuit.

When I started to install the head unit though the case started to spark whenever it touched anthing attached to the chassis, even though the Isolation switch was off. It seemed like the case of the headunit case becoming postively charged.

As such I've got 2 dead head units that I'm really cheesed off about.

I'd like to have a go at fixing them if possible but I don't have a clue where to start.

I'm also really confused as to what has happened here. If I could get the head units working I'd happily just run them off the Ign and deal with having no memory as this is how it used to be.

I just wants music back in my car - I really hope someone can offer me some assistance!

Many thanks in advance,
Anthony

IIUC, the parts in bold should give answers to the problem.
Along with the underlined part...although it's the reverse of what you think. The head unit case is still ground, in relation to the battery, but the rest of the vehicle is now at the positive level.
If you take a ground from the battery-side of the isolation switch, to the head unit, you are creating a new switch to ground via the head unit chassis and the vehicle chassis...

EDIT: Basically, you are trying to reconnect the battery THROUGH the head unit..

 

[cantfindausername]

I'm a little confused as to how I can get around this then.

I'd like to draw out my wiring plan so I can ensure I'm describing it properly and to get some advice on it. If it turns out I can't do what I'd hoped then I'll live with it. I appreciate your time and help in this.

Thanks,
Ant

 

[cantfindausername]

Ok, excuse the poor attempt at the diagram...

I would think this would work, could someone explain why its not?

Thanks,
Ant

**broken link removed**

 

[cantfindausername]

I think I might understand this now. Kept me awake a lot of the night!

The Isolation relay cuts the main chassis/battery connection, but where I'm connecting the distribution block directly to the battery and then the head unit to the distribution block, when the head unit touches the chassis it is bascially remaking the main chassis/battery connection.

If my understanding is correct, (I'd like someone to confirm my thinking) then I am thinking I'll need to connect the distribution block earth to a chassis point and live without a "constant" feed to anything.

Am I right?

Thanks,
Ant

 

[Mickster]

I think I might understand this now. Kept me awake a lot of the night!

The Isolation relay cuts the main chassis/battery connection, but where I'm connecting the distribution block directly to the battery and then the head unit to the distribution block, when the head unit touches the chassis it is bascially remaking the main chassis/battery connection.

If my understanding is correct, (I'd like someone to confirm my thinking) then I am thinking I'll need to connect the distribution block earth to a chassis point and live without a "constant" feed to anything.

Am I right?

Thanks,
Ant

You have it understood correctly.

Basically, your head unit was creating a new path to chassis ground. If you had taken a voltmeter and connected the -ve probe to the head unit chassis, then connected the +ve probe to the vehicle chassis, you would have read battery voltage.

 

[cantfindausername]

Thanks Mickster, I've changed the set up now so the Distribution block is earthed to the chassis. This means I can't have any constant feeds which is a bit of a downer as that was sort of the reason I started the whole thing. Guess it wasn't as straight forward as I though.

We live and learn though. Thanks for the advice.

Regards,
Anthony