Amp Power Turns Off Shortly After Turning On

[Skydronaut]

I have a 1000w amp driving two kenwood 12 subs.

The drivers are running on channel 5, with the head unit running into 5 and 6. This setup worked fine for two weeks, but randomly died. Every time I try to turn it on, the pwr light fades off after about a second, and the prt light stays on.

Thought it was a loose connection issue; I got a crimping tool and re-crimped the +/- wire blades, and re-sanded the chassis ground surface, installing a proper ground bolt thru the chassis while I was down there. Didn't fix it.

What do I do next?

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[dubstepper1000]

Have you checked your fuse under the hood? checking voltages with a DMM would probably shed some light on the subject.

 

[Skydronaut]

Well, the amp's integrated fuses are not blown, the amp's inline power fuse is intact, and the h/u is still fully operational. The amp is still getting power, so I don't believe there's any blown fuses- the darn thing just won't stay turned on!

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[dubstepper1000]

Can you check the voltage at the terminals when it starts to act weird? I've had the same problem where it would be going in and out of power because the fuse was damaged, at first glance it looked fine but further testing proved that i neede a new fuse. make sure you have a good healthy voltage going to your amp. If that doesnt work, check the wire going to speakers, even one tiny strand connecting the two with short it and cause the amp to do funny things

 

[Boomin_tahoe 5,000+ posts]

What's your electrical like?

 

[Skydronaut]

I'll check the voltage after work today (about eight hours from now). I guess I'll also check the resistance of the fuses for any unexpected ohms.

Also, the electrical is wired pretty well. Most wires are properly installed under the trim and dash, and zip-tied in places where it could move around and cause problems. The wire blades are only crimped, not soldered, but do not jiggle or give at all when tugged. The positive is bolted to the stock battery post, and the ground is bolted to the chassis. The accessory wire is spliced into the head unit power wire.

Let me know if I missed any details you were looking for.

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[Skydronaut]

I measured the voltage on the power line when the car is put on accessory mode. At the 200m range, the dmm display reads 18.3 each time. Seems like too much voltage? After a second, the voltage drops back off to zero. When the car is turned off, a short reading of .7 is displayed, and drops off to zero. I haven't touched a dmm in about six months, so could someone help decipher what this data tells me?

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[dubstepper1000]

the range you use indicates the maximum voltage it will read, so the 200m will read up to 200mV or .2V. So the 18.7 means it is .0187V, are you sure it is set to DC Voltage? If it is set to AC then it will give a value close to zero. The icon looks like a line with another dotted line next to it, use the setting that has a max of 20 which is common of most DMM. Test it when the car is running, you should get something in between 13 and 15 volts when the alternator is running.

 

[Skydronaut]

I am absolutely certain I tested the dc voltage at the 200m range. Even if I'm only getting .0187vdc, I don't understand why it only gets voltage for a second before losing signal... Should I try measuring amperage to see if it's shorting somewhere, causing the voltage drop?

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[dubstepper1000]

It wouldn't hurt, but it might be easier to sniff it out by testing the voltage as you go along, first check the voltage on the battery terminals, then from the negative terminal to the closest side of the inline fuse, and again for the furthest side of the fuse. Do this when the car isn't running, and when it is. If you are getting that low of voltage across the amp there is something wrong with your wiring. Something i like to do is to take the whole thing apart including the fuse and battery connections and just do it all fresh. Also, when you are conducting these tests, unplug the speakers and the RCA's, try to get it to run with only the power, ground, and remote. As for why it is turning on and off I'm not entirely sure, most amps won't even power on without at least 10V, unless you are not using the DMM properly.

 

[audiobaun 5,000+ posts]

Check the ohm load on the subs..Make sure your wiring is stable on the subs.What size wire are you using for supply and ground?? What head unit are you using?What battery are you using under the hood?Stock alternator,or aftermarket HO alternator for what vehicle?What size wiring being used for the subs?What size inline fuse being used at the battery, and are you using a distro. block(solid, or fused,size and what size fuses/type(ANL,AGU,Mini ect,type of wiring/brand and size),ect.

 

[Skydronaut]

Supply and ground are 4 awg. Kenwood kmm-108u h/u. Stock battery, stock alternator, 2003 Cube, no distribution block. I think the sub wires are around 10 or 12 awg, not sure. The wiring kit was a 4 awg kit, so I'm pretty sure the fuse is at least above 100A... I tested all the fuses the ge other day, and all read pretty much exactly zero.

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