Sub only works when ground cable first gets connected?

bokdaddy

Hey guys, after taking the advice of the masses I got a 2-channel amp to bridge to my Infinity 10". I picked up a Profile AP400 from Crutchfield and hooked it up today. But I've been having a very odd problem. It all seems to be hooked up correctly. But signal only seems to be going to the sub for the first couple seconds after I connect the ground wire to a part of the cars frame. I'll get a quick burst of signal and it'll die out immediately. What I don't understand is that the red light on the amp stays on but the signal goes out. Any ideas what might be causing this?

Edit: If it matters I was using a Sony 2-ch amp before this that was having no problem.

exalted512

maybe the ground point. Scrape off some paint with a screwdriver and put 2+ screws in the ring terminal on the ground wire...see if that helps
-Cody

bokdaddy

I thought it might be the paint so I briefly attached it to the trunk latch, which is unpainted. And had the same thing happen. And what about the light? Does the fact that it stays on mean anything?

I'll have to do the scraping tomorrow. It just seemed like a weird thing to have happen. I would have thought that if it was the paint it would either get a weak signal or get no signal at all. Not a spurt and then die. But I'm new to this.

Vestax

Do you know if you safely loaded the correct resistance to the amp? If you have a digital multimeter, you can test the resistance (measured in ohms) and see if you a total of a dc resistance of close to 4 ohms (assuming you're wired the sub into a mono load of the amp). A protection light only goes on if the amp sees something below it's stability or in other case where there's a possible short.

bokdaddy

Actually it's not the protection light. That light stays off. It's the light on the top of the amp that is definitely just for looks. It's only on when the power light is on. But if the ground wire isn't connected it goes off.

PolkThug

Turn the gain way down on the amp and see if it still does it.

Vestax

bokdaddy wrote:

Actually it's not the protection light. That light stays off. It's the light on the top of the amp that is definitely just for looks. It's only on when the power light is on. But if the ground wire isn't connected it goes off.

It should go off because the ground completes the circuit in a DC electrical system. Just curious, did you get voltage coming from the turn on lead when you turn on the HU?

bokdaddy

Well, I've tried scraping the paint, and I've tried turning the gain down. Scraping the paint seems to have made it last slightly longer before the signal to the sub goes out.

And I guess I might sound a little confusing. The protection light has never been on. It's the glowing light on the top that goes off. The LED light I guess? Well it's that light that was going off, and now it goes out everytime the sub hits hard when it first powers on. Once the signal to the sub dies out it stays the solid bright red. Is it possible that this is an issue with the battery that might be fixed by adding a capacitor? And by problem I don't mean the light, I mean the loss of signal.

MacLeod

So the amp's power light stays on, the protection light never comes on but when the bass hits the sub cuts out and the cool looking non functional light goes out with the signal.

Sounds to me like youve got a faulty amp. Luckily you bought it thru Crutchfield which has some of the best customer service around. Get in touch with them and see about a swap out.

98thumpin

sounds like the amp to me too.

1996blackmax

I've been dealing with Crutchfield for many years, the couple times of I had problems they were very helpful.

bokdaddy

Well, it turned out that it wasn't the amp. It was the wiring. So I took it to Circuit City to have things fixed up and to have an amp hooked up to my 6x9's too. And now it has turned into a nightmare. I spent 280 bucks to get two amps done and now my cruise control and my rear defroster don't work. I wish I didn't have to point the finger, but my cruise control was working fine on the way to Circuit City. I know because I have to take the New York State Thruway to get there...

98thumpin

ouch that sucks mann, id be gettin them to do some fixing on it.

MacLeod

Hmm, I wouldve thought it was a faulty amp. Dont know how wiring could cut out the signal and the top LED light but not the power or protection light. Weird.

I guess youll have to take it back to CC and let them have a look at it and see if they can figure out how your cruise control got screwed up.

A good rule of thumb is to never let Circuit City install anything for you. They used to be the best trained installers out there back in the late 80's, now theyre mostly $7/hr high school kids. Stick to a local, custom shop. Those guys will almost always be much better.

exalted512

before you go back, disconnect the negative wire coming off the battery for about 15 minutes. Every now and then some cars dont like having anything aftermarket put in em. My guess is if you did that and it didnt work, id check your fuses. Itll save you a trip back to CC and 95% of the time itll fix your problem
-Cody

98thumpin

i didnt think of that he is right,

1996blackmax

Good idea to check the fuses Cody.

bokdaddy

Thanks Cody, but I was already on my way. The boys in red said they plugged some cables into the wrong spot. I'm pretty frustrated but at least it's fixed.

MacLeod

Well at least they didnt try to BS you and tell you it was something you did and not them. Thats stand up of them.

98thumpin

yeah it is

exalted512

1996blackmax wrote:

Good idea to check the fuses Cody.

yea, after you work at a car audio shop long enough you see some weird ****.
-Cody

98thumpin

i can only imagine

1996blackmax

I have also seen weird and very very weird working in the health care field.

98thumpin

i bet that too.