Car amp wiring problem

[ChadTower]

Okay, a friend gave me a decent Sony amp and a couple of boxed speakers.  I want to put them in my trunk.  After much reading on how to do this...

I ran the power wire from the battery, through the firewall, and under the driver's side door moldings all the way to the trunk.  There is an inline fuse about 6" from the battery.

I ran the audio line from the head unit, under the passenger side moldings, all the way to the trunk.

I forgot to run a remote line.  When I noticed this, I took out the head unit harness, found the remote line (blue).  I undid the connection between the two blue wires, twisted the remote wire to the amp with one of the blue wires, and then put them into a crimp connector (two on one side, one on the other).

I still get no response from the amp.  

Possible problems I see:  maybe a bad crimp job on the remote line; the amp is missing some of the terminal screws so the remote line was just wrapped around the screw hole (I intend to clean this all up when it's working).

What else don't I see?  When connecting the remote line to the harness, in the absence of a power antenna, does it need to be connected to the car end of the wiring at all?  Is the crimp connector a totally wrong way to go?

(yes, I'm aware there is the small possibility that the amp itself doesn't work)

[SoundDoc]

First do a quick test of the power.
Do you have a multimeter? If not, get a tail light bulb and some wire...

Check the amp, do you have a proper ground wire to it from the battery, or the chassis?

Now check for 12V to power it, either with a multimeter check between the 12V terminal on the amp to the Ground terminal. 12V? If not, check the 12V terminal to some bare metal or a screw into the chassis. 12V now? if so, your ground is bad.
No multimeter? take a tailight bulb, and hook a short legth of wire to the two connections on it (I have a taillight bulb in its socket I ripped out of a old car just for this purpose) Check the same as above, Light=12V. Sometimes the taillight bulb is a better check than a multimeter as it puts a load on the circuit. IE, you could have 12V on the meter, but if the ground connection or power connection is bad, trying the same with the lamp won't light it as the connection can't handle any current.

OK, so we now have 12V and ground verified correct? Check the Amps fuse. is it good? Now lets check the amp. take a short length of wire, and connect it to the remote terminal. touch this to the 12V Terminal. Does the amp power up/click/light up? if so, your amp is fine. Take your multimeter (don't use the bulb here too much load) and turn on your deck. At the end of the remote wire near the amp, do you have 12V between the remote wire and ground? If so, you should be good to go, if not, check for a inline fiuse on the remote cable, check right at the deck remote out for 12V when the deck is on. If not the deck may be bad....

Now before we rule out the deck, quick question..... (I love this one cause i've smacked my head so many times before with it in the past). Is this a factory deck? If so, (or if its a cheaper deck) is the "remote" wire your tying off called "remote" or "Antenna"? Many decks, escpecially older ones may have an antenna out, as well as a remote out. The difference being, that the "Antenna" power wire ONLY has 12V when the radio is on AM or FM to extend the power antenna. When in Tape or CD modes, the line is dead. I had a guy I did a install for when I first started like 14 years ago, I did a nice install, hooked up and tested everything. And the next day he brought it back, every time he put in a tape (CD's wern't big then) the system would go dead..... Took me a while to figure it out, I thought the deck was bad, but there were two connections on it, one for antenna, and one for remote.

Good Luck! Let me know if this helps!

SD

[ChadTower]

Quick question, which may be my problem here:  will the unit work at all without a ground connected?  I haven't done that yet.  I had assumed ground here is mainly a safety feature.  Is it to complete the circuit?

The deck is a Blaupunkt San Jose MP41, less than a year old.  The docs indicate the blue wire is combined power antenna/remote amp line.

[SoundDoc]

Yes, not having a ground is a very bad thing indeed......

You NEED a ground, its not for safetly, its to complete the power circuit. Hook it directly to the chassis of the vehicle where you can get a good connecton. Its just as, if not more important to have a good ground connection than a good power connection. A bad ground will lead to noise problems, lack of power, as well can damage your equipment.

Hopefully no damage is done yet. What can happen if you loose a ground (or don't have one) is that the amp through internal connections tries to get that ground through other means, usually the shields (ground) of the RCA cables, back into the deck, and through its circuit board, and small ground wire. When your talking about trying to Sink >10A in most cases (up to whatever your amp's fuse is) though the RCA's and the head unit, you can (and I have seen) melted RCA's, Smoke, blown decks, fried amps, etc....

Its just like any circuit, you always need a return path for the power, It needs to get back to the battery to complete the circuit, and it will take whatever path it can to get their. In the trunk, the easiest way to get a good ground (rule of thumb, if you use X gauge for power wire, use same gauge for ground) Is to take a large wire lug, lie a  1/4" wire lug crimped onto the ground wire, and find a bold in the trunk to put it under, make sure you scrape the paint off the location you are going to connect to, to ensure a good connection. I have seen (any fixed) many systems where guys run the biggest pheonix gold power cable from the battery, through a 100A fuse, into the trunk, and then hook a short piece of 12 gauge wire from the amp to a screw they find (usually th ground screw for the tail lights) this won't do.
Read linky for good info:
http://www.bcae1.com/battgrnd.htm

Good Luck!

sd

[SirPeale]

Quick question, which may be my problem here:  will the unit work at all without a ground connected?  I haven't done that yet.  I had assumed ground here is mainly a safety feature.  Is it to complete the circuit?

Uh....yeah.  The entire metal frame of your car is ground, and without it likely won't do much.  You connect the + side to either battery (or a wire known for +) and ususally ground to  the car chassis.

[ChadTower]

Got it.  The thing I'm not seeing yet, though, is how the power returns to the battery via the car chassis?  Or does it just have to go SOMEPLACE?  I would have thought it would go back to the - terminal on the battery if it needed to return there.

[SoundDoc]

Pull out your flashlight and start looking under the hood....  
Theres a big cable from the negative terminal on the battery that will either directly connect to the chassis within a few inches, or it will head down to the starter where it ties to the chassis. (depends on the manufactuer and grounding of the engine).

Thats your return path. Your circuit runs from the battery, to the trunk, through your amp, out the ground terminal, into the chassis/Frame, back up to the front, into the ground wire, and back to the negative terminal on the battery.

Most all vehicles use the chassis for ground. Its easy, and most sensors in the vehicle need a ground connection, and since the vehicle is mostly steel, There you go!
You just have to watch some european cars, not sure if they still do it, but just like those crazy english drive on the wrong side of the road, some of their cars use the frame as the positive connection. (I haven't seen this, but I have heard about it enough to make be believe it to be true). I'd hate to accidentally try and boost one of those cars.......


Let us know hoe it goes.

sd

[ChadTower]

Wow.  How is that safe, exactly, considering people touch the chassis?

[SoundDoc]

its only 12VDC, you'd never even know. if your not completing the circuit, theirs no current flow.
Its all in the potential between 2 points, not the actual voltage.

sd

[ashardin]

My ground (or lack thereof) was a headache for me on my install that I did a few weeks ago.

4 gauge power and chassis ground, and then the power and ground had their seperate distribution blocks (these are hidden from normal view) on an amp rack.  Hooked everything up, double checked cxns, and then put it all into place.  I could only get a little bit of sound and a lot of distortion.  So I started to troubleshoot.  Deck amp sounded fine on its own, but when I powered on the bass amp, it all went to hell.  Couldn't figure that out at all.  Everything looked good.

Stayed stumped and left it overnight, started working on it the next morning and still couldn't figure it out, so I proceeded to tear it all out, thinking maybe the a component went bad on me (everything was out of my old car so it should have been fine).  Got to the distribution blocks, and the ground had come loose when I put it together.  So the block itself was strong enough to ground out the deck amp itself, but add the JBL 1200.1 and it was not enough, thus giving my bad power and bad sound.  I spent hours troubleshooting a 15 second fix.  I was a little pissed about that!

Always triple check all connections!!!!