amp won't turn on, strange power drop (n00b)

[dp209]

This is my first attempt at installing an amp. It's a small 400w Pioneer amp. I've done lots of household electrical work and a lifetime of computer builds, so I feel I'm fairly competent with electronics //content.invisioncic.com/y282845/emoticons/tongue.gif.6130eb82179565f6db8d26d6001dcd24.gif

I've installed plenty of head units, however, this is my first attempt at installing an amp...

When I turn on the ignition, the amp's light turns on then off quickly. //content.invisioncic.com/y282845/emoticons/mad.gif.c18f003ab0ef8a0d9c27ca78d77a6392.gif

I've checked all fuses, everything's good.

Here's the strange part (strange to me I'm hoping it's obvious to the experts out there)...

I've got my multimeter out and I'm taking readings. With the car off, the reading at the battery is about 12.67V. The reading at the amplifier is about 12.55V. If I turn the key (don't crank the engine, just turn on ignition), the amplifier tries to turn on (the light flashing on/off) and my reading at the amplifier drops to 8V. //content.invisioncic.com/y282845/emoticons/confused.gif.e820e0216602db4765798ac39d28caa9.gif (So it's obvious the amp won't turn on with only 8V, but not obvious to me why there's only 8V at this point.)

If I turn off the key, it slowly builds back up to 12.55V (takes about 2-3 minutes). //content.invisioncic.com/y282845/emoticons/confused.gif.e820e0216602db4765798ac39d28caa9.gif

If I remove one of the leads to the amp (power or ground), then my reading at those leads immediately jumps to match the reading at the battery (12.67V).

The behavior is the same (albeit with higher readings at the battery) if the engine is running.

To me, this is strange. I'm hoping it's an obvious symptom of a problem and that someone can point me in the right direction for diagnosis.

Thanks!

UPDATE: Diagram: http://yfrog.com/13wiringg

Click to read more...

 

[westman995 10+ year member]

Did you double check all your connections? It almost sounds like a ground issue. Check your ground wire and make sure its got a good connection on the chassis.

 

[dp209]

I've posted a diagram here:

http://yfrog.com/13wiringg

I'm grounding direct to battery... all connections seem fine.

There's a piece of bare metal nearby that I was thinking to trying to ground to, to see if that makes a difference.

I've already disconnected all speakers to make sure one of them wasn't shorting out or something. Same issue with no speakers connected.

 

[westman995 10+ year member]

It should work if its straight to the battery. So the ground shouldnt be the problem if all connections are good. You may want to take a small wire, and just straight wire the remote to the power wire to see if its possibly your remote lead on your stereo or something. And you made sure ALL fuses are good?

It really sounds to me like your not getting power to the amp for some reason. Since the light goes on, and then right back off. The remote wire will supply power to turn the LED on and then its gone. So check the fuses i guess if you havent already done so. I dont know what else to tell you. If that doesnt work, hopefully somoeone else will chime in.

 

[jpexpc 10+ year member]

You're ground shouldn't be that long. 2-3ft max.

 

[dennit469 10+ year member]

had this happen a few times bud, its the connection on your battery, promise, and EVERYTIME it does tha same as you, 12v with amp off, 8 v with it on, its not a strong tight connection on the battery. double check and triple check that.

 

[westman995 10+ year member]

Tho the ground usually is not set up this way, and i would recommend to ground it to the chassis normal. It should still work fine with the ground straight to the battery, and seeing as how the amp is not a huge one, it shouldnt matter a whole lot. Either way, it would run set up like that. So like above im thinking it has to be a connection issue.

 

[dp209]

Yup, thanks everyone. It was the ground connection. Finally narrowed it down to the connector at the battery. Cut it off, put a new one on and we're all good!

 

[westman995 10+ year member]

Good to know. I would however lose the long ground wire and ground it to the chassis instead for any problems that may possibly occur..

 

[Twisted_0912 10+ year member]

Good to know. I would however lose the long ground wire and ground it to the chassis instead for any problems that may possibly occur..

noob. a straight battery ground is the best kind