Voltage Drop When Amp Turns On

[irootbeer]

Hello whoever is reading this,
I've been having some issues with a subwoofer setup in my 2015 V6. I have everything wired up correctly and my amp turns on, however it turns on into protection mode because it looks like the voltage to my amp drops to ~9V when remote voltage is applied. It's very frustrating because what little time I've had recently has been spent troubleshooting and I cannot figure out what the deal is. I have my ground attached to the bolt holding down the back seats which is used by most people that do installs for this model. This is what I believed the problem to be, but I went back and sanded the metal to a shine and redid the connections to no avail. This is what I'm looking at in terms of voltage at the amp:

Amp off (ground to B+)

Amp on (ground to B+)

Amp on (REM to ground)

I'm pretty desperate for help at this point. I've only done 1 install in the past (on a mustang coincidentally) so forgive me if I'm missing something obvious. If I am please let me know :headbonk:

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[vnzbd]

I would take a quick look at your fuse connections. One time I had an inline fuse that did not make a good connection within the holder and it caused all kinds of havoc. My voltage read great until the unit turned on and it dipped after. The poor connection could not carry the current and a voltage dip was present.

 

[irootbeer]

I would take a quick look at your fuse connections. One time I had an inline fuse that did not make a good connection within the holder and it caused all kinds of havoc. My voltage read great until the unit turned on and it dipped after. The poor connection could not carry the current and a voltage dip was present.

Thanks for the post. I went out and checked all the fuses from the engine bay to the passenger kick panel but everything was in order. While I was there I checked the voltage from the ground terminal on the amp to the other ground spot in the spare tire area. All I read was a couple millivolts so I believe my ground is solid. I also forgot to mention I'm running 4 gauge power wiring so there shouldn't be any limitations there

 

[Keith_PDX]

So when the amp turns on you get a 3V drop. Are you sure the amp is good? Your wiring is obviously fine as the voltage is fine when the amp is off. Your wire is plenty large and if you had a bad fuse causing a voltage drop you'd see that all the time, not just when current is flowing. Are you doing this with the car running or off? When the amp is on (and you have 9.49V at the amp), what is the voltage at the battery?

 

[irootbeer]

So when the amp turns on you get a 3V drop. Are you sure the amp is good? Your wiring is obviously fine as the voltage is fine when the amp is off. Your wire is plenty large and if you had a bad fuse causing a voltage drop you'd see that all the time, not just when current is flowing. Are you doing this with the car running or off? When the amp is on (and you have 9.49V at the amp), what is the voltage at the battery?

I just got the amp 3 days ago brand new I'm hoping its not busted lol. I've tried testing running and on acc to similar results. I checked the voltage at the battery the last time I was messing with it and on the posts it measures 12.2V but if I measured from the nut holding the power wire it was at around that 9V mark

 

[SQ_S550]

Disconnect your speakers and check voltage. If that does not work check the continuity between the +12 and the remote on the amp.

 

[irootbeer]

Disconnect your speakers and check voltage. If that does not work check the continuity between the +12 and the remote on the amp.

The speakers were disconnected for my tests. I got like around -1V when I tested that earlier, don't know what that means though

 

[SQ_S550]

Normally if you get a value when testing continuity then the two points are connected electrically, did you hear a beep when you tested continuity of the 12v and the remote inputs? If you did the amp is bad.

 

[irootbeer]

Normally if you get a value when testing continuity then the two points are connected electrically, did you hear a beep when you tested continuity of the 12v and the remote inputs? If you did the amp is bad.

Interesting I will check that out in the morning, thanks for the help man :cheers:

 

[Gurjit]

with the amp on
put the red lead of the meter to the amp positive cable screw and put the black lead to the positive post of battery, this will determine if the power wire is bad

do the same thing with the ground side, red lead on the gnd of the amp cable screw and black lead to the battery ground post

your readings should be around 0v, anything over 0.5v is a fail
i would use longer jumper cables to give you the extension you need from battery to amp

 

[irootbeer]

So turns out the positive terminal on the battery had some corrosion on it that I assume was causing the voltage to act the way it was. I changed the connection point for the fuse holder also and between those things it finally turned my amp on. Unfortunately the speaker isn't outputting any sound (of course) but i'll figure out the problem eventually. Thanks to everyone that took the time to help me out

 

[vnzbd]

So as guessed with the power wire. Only makes sense since the remote wire stayed steady at 12v. That shows that the ground was decent at worst. That leaves either a defective amp in which I would believe would ace the fuse or fry the amp in which case you would smell BBQ. There is a big difference in the power wire carrying the voltage without load and with load. A loose fuse or corrosion is resistance hence the voltage drop when current is applied.

 

[irootbeer]

So as guessed with the power wire. Only makes sense since the remote wire stayed steady at 12v. That shows that the ground was decent at worst. That leaves either a defective amp in which I would believe would ace the fuse or fry the amp in which case you would smell BBQ. There is a big difference in the power wire carrying the voltage without load and with load. A loose fuse or corrosion is resistance hence the voltage drop when current is applied.

Yea it all made perfect since as soon as I saw all the corrosion. I couldn't believe how bad it was, the entire underside of the contact was covered in a thick layer of it. Made the skin on my fingers sizzle a little when I grabbed it on accident Just a quick question about my new problem though, would I troubleshoot the speaker connections on the amp with a DMM? If so what would I be looking for? All the wiring I have was purchased new so I don't think it has anything to do with the RCA's

 

[vnzbd]

I would check the voltage at the rcas going into the amp. use your DMM on an AC range. As you raise your volume your voltage will raise as well. expect between 2-9 VAC. Check both L and R channels. If the voltage changes as described look at the amp. If it does not then look towards the head unit.

 

[irootbeer]

I would check the voltage at the rcas going into the amp. use your DMM on an AC range. As you raise your volume your voltage will raise as well. expect between 2-9 VAC. Check both L and R channels. If the voltage changes as described look at the amp. If it does not then look towards the head unit.

So I'm getting voltage in from the RCA's and voltage out from the speaker terminals on the amp. The subwoofer just BARELY moves, doesn't make sound or anything. Adjusting the knobs on the amp barely makes any difference. Could this be because I'm using an old subwoofer? Just fyi its the subwoofer from a Kicker Bass station that I got for free a long time ago. I measured the resistance value on it and it looks like its exactly 1 ohm. I don't know if my amp is rated for something that low, I'm using the Rockford Fosgate R500x but from what I understand, it would make the subwoofer draw more power in that case, right?

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