Mazda Mike

So I'm on my second amp and everytime I turn on the car, the amp turns on, lights up as normal, as soon as sound comes on, it turns off. The gain on it is about 20 percent. Sometimes it does stay on and has sound and will either A)Remain on for the duration of the ride or B) shuts off after some time.

Wires have been checked and there is no crosswires touching, no fuses blown, the amp fuse has been replaced as a precaution with the same fuse gauge. I also haven't changed the glass fuse in the power since it still looks fresh.

So what would be a more likely problem? Would I need a cap to help power it? But if I did, why would my last amp power on and work for the time I had it?

*Little history, none of my amps are more than 800 watts; My last amp died when i was switching from a sub to my 6x9s to hear the difference in sound*

Help!

firebirdude

iTrader: (3)

I'd really need to get in there with a multimeter to see what's going on. I suggest you do the same.

What is the amp pushing now? Do you have the exact model number of the speakers? How are they wired up?

Mazda Mike

2-ch Amp *American something* is 800 watts total, pushing 1 12in sony explode. Hooked up 1 channel to the sub, not bridged.

I do have a mm, should everything be reading 12v?

firebirdude

iTrader: (3)

Around 14V with the car running.

Wait for the problem to appear. Does the power LED on the amp turn off? Change colors? Start right at the amp's inputs. Test both the power lead and the remote lead. Remove the speaker wire going to the subwoofer and set your multimeter to test resistance. Touch the leads to the speaker wire and see what you get. 2 ohms? 4 ohms? 1 ohm? Maybe even provided a known good source of audio using an iPod with RCA leads going directly to the amp (remove the headunit from the equation).

And not to sound like a jerk, but sounds like it's a low quality amp. Wouldn't surprise me if the amp really was having problems.

Mazda Mike

No offense taken, I just wanted an amp to provide a little bump, I have car seat in the back lol....

But everything lights up normal but then turns off. I think the board on it went bad. I already took it back and got a credit for it. I'm gonna look around locally today to see if I can find one in a better condition.

Mazda Mike

Ok, so I checked the wires and connections, everything is fine. Now, on my 3rd amp, it comes on sometimes but if I turn up the volume, it turns off. Keep in mine, the amp is only on about 50%. Any ideas?

firebirdude

iTrader: (3)

The gain **** being only half way doesn't mean everything. It's a voltage sensitivity **** to be matched with the input signal voltage.

You never answered, what impedance are your speaker(s) presenting to the amp? Have the exact model number you can give us? You using an aftermarket headunit? LOC off the rear speakers? Other?

Just so we're clear, I never suspected this was a connection issue. You're not going to find this problem with your eyes.

Mazda Mike

The voltage checks out, 12v, the amp is a Thump 800 watt (not sure on the model, but I'll check during lunch), 4 ohms all around, it is based on the BOSE system, and LOC is hooked up to the rear speakers.

Anything else to help?

Mazda Mike

I disconnected the sub and turned the volume on the headunit all the way up, the amp didn't turn off from a power stand point where as in the past it did. Next up, is to test out the sub but I'm feel that the sub is gone. Does this sound pretty reasonable? Like a bad coil in the sub itself that it might be causing the amp to either turn off or go into protection mode?

firebirdude

iTrader: (3)

When an amp plays for awhile, then cuts off when the volume is increased or just over time.... it's usually one of three things.
1) The amp is overheating. Thermal protection. Couple things could cause this, but thermal protection is what stops the music. Don't think that's what is going on here.
2)Low voltage protection. As we all know, the harder you crank the amp, the more demand it places on your vehicle's electrical system. A lot of amps are designed to cut off if voltage EVER drops below....say 11V. Check this with the car running. Shouldn't be below 13V ever with the car running.
3)Short circuit/over current protection. This happens when the amp is presented with an impedance that is below it's capabilities. Such as using a 1 ohm load on a bridge amp for example. Also remember that music is dynamic. The impedance fluctuates greatly as music is played. Sometimes an amp may be able to handle a 2 ohm load.... until you crank the volume and demand a ton of current. This is a possibility in your case. And yes, if a coil is blown, that will change the impedance presented to the amp. Test it with a multimeter while disconnected from the amp. 4 ohms nominal to one channel of a 2-channel amp should obviously be fine. Should be fine even if bridged, but some amps still have problems with this.

If nothing else, find a friend with an amp. Pull the cars trunk to trunk and run your speaker wire over to his amp. Give it a whirl.

firebirdude

iTrader: (3)

Just realized you're in Florida. Where?

Mazda Mike

Orlando area.

firebirdude

iTrader: (3)

Ah. I'm too far to meet with you.... and the friends I have there aren't car audio specialists.

Mazda Mike

Where art thou?

firebirdude

iTrader: (3)

Recently, I spend most of my time in Melbourne and Gainesville. I'm in Orlando sometimes, but usually on business and pressed for time.

Mazda Mike

aww shucks.... lol

I'm gonna try a different sub tonight. Hopefully now, I have it pin pointed on where the problem lies.

Mazda Mike

Soooooooooooooooooooooo after getting frustrated with the same problem again, I went around to my rear passenger seat to open up the slot in the middle of the 8 to see if a wire came undown. As soon as I kneel down, the amp came on, no problem.

Then it hit me like a sack of bricks.

The ground was SLIGHTLY loose.

After about laughing myself silly for a good 5 minutes, I got a philips and tighten that *^$#!!#$%^& think until my hand was sore. Now, I can enjoy bass once again...

firebirdude

iTrader: (3)

Glad you got it figured out.