HU come on voltage at amp, drops from 12.9 to 5.1?

[Sierra08! 10+ year member]

I got a friend who did not know why his bass amp was not running, I used a volt meter at the amp, and the battery, both 12.9, as soon as the HU turned on, the voltage at amp drops to 5.1, disconnected the remote wire and the amp has 12.9, put remote on drops again, any ideas help?

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[blackbonnie 5,000+ posts]

he doesnt have sufficient electrical for his amp to even run when its on maybe...

what amp is he running?

what car?

whats his electrical consist of?

 

[Sierra08! 10+ year member]

He has a 66' Caddie show car, has some JL's and has a MTX amp, also he has a Hynoptic Zen Amp, never heard of it, but it was free, tried both, all the battery runs is the headlamps when on at night

 

[audiobahnuser18 5,000+ posts]

what awg wire he running?

 

[Sierra08! 10+ year member]

8 gauge, all around, the amp is only 150x2 at 14.4 so i assume 100x2 at 12.5, everything used to work, until he got it out of the shop, it was being painted

 

[audiobahnuser18 5,000+ posts]

Run 4awg wire or 1/0awg even better. what subs exatcly is he running? how many? any extra batteries?

 

[Sierra08! 10+ year member]

2 10 JLw1's, wired to 4 ohm stero, (2 channel amp) (class a/b) the thing is the amp get 12.9 volts and as soon as the HU is on, the amp sees 5.1, could it be something with the remote

 

[Haunz 10+ year member]

The voltage at the amp's power terminals drops to 5.1 volts??

BAD GROUND or bad power connection somewhere.. possibly a loose fuse ??

 

[Sierra08! 10+ year member]

Yep, soon has HU is on, the power light on amp comes on but, that is all, also did an ohm test on ground, and its almost zero, no problem there, (and the ground wire about 12 inches long)

 

[n2audio 5,000+ posts]

This doesn't seem to be a charging system problem (12.9 is with engine off, right?)

Check the fuse holder and fuse - agu's can be defective at the end caps sometimes and the element itself looks fine. I actually had an agu fuse HOLDER fail once. It was weird -- didn't seem possible, but the spring mechanism that held the end cap somehow was not conducting even though there was plenty of metal to metal contact.

 

[jdawg 5,000+ posts]

how does the underhood wiring look? when he has the headlights on what is the voltage? Is the battery ok?

 

[jco1385 5,000+ posts]

swap in a second HU.

sounds like a bad HU

 

[GAM3OVR 5,000+ posts]

I'd hook up an ipod to teh amp directly and see if it plays normal like that.

If it does you got a bad HU

If not, bad amp wiring/amp

 

[jco1385 5,000+ posts]

I'd hook up an ipod to teh amp directly and see if it plays normal like that.
If it does you got a bad HU

If not, bad amp wiring/amp

it's not a signal problem, it's the remote wire.

try jumping the remote wire from the 12v +. without the HU remote hooked up.

if it still drops, bad amp. if not bad HU

 

[GAM3OVR 5,000+ posts]

I've had my old HU remote + go

I just ran a switch, till I got a new 1