Voltage Problems, Please Help!!!

[rlambert02 10+ year member]

Ok so here's what i already have:

Mechman 220 HO alt

Big 3 wiring

optima yellow top (front)

XSd3100 (rear)

AT OFC 0g throughout

Full copper terminals soldered

Problem: At idle my car sits at 13.8 (dont most cars idle at 14.4?) but when I put my saz-3500 in a week ago it cut out after 3 seconds of play, thought i blew the fuse, then today when i was redoing my build i noticed the fuse was fine so decided to some testing. Hooked up the 3500 again tuned with a dd-1, at it was dropping down to 11.2 at just a little over half volume.

With what I already have shouldn't i be able to hold at least 12v just fine.

Tomorrow im going to do 2 runs of 0g from the front to the rear, but do i go from the front batt to back batt or the alt directly to rear batt.

What should i try to do, get rid of the yellow top and upgrade the front battery? I'm really trying to not add a second rear batt cuz im having a lot issues with rear weight and ride height.

Any help or advice is appreciated. Thanks guys.

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[gckless 5,000+ posts]

Idle seems low at 13.8V. Should be higher than that with that alternator. Go back and triple check all your connections under-hood. Ground, alt, battery, all of them.

 

[rlambert02 10+ year member]

I did that. Should i check the voltage directly from the alt and if it's at 13.8 what do i do?

 

[gckless 5,000+ posts]

Sounds like a wiring issue. Where were you measuring the voltage from? In back by your amp or up front?

 

[rlambert02 10+ year member]

checked both, I only drop like .1 sometimes from the front to the back battery

 

[gckless 5,000+ posts]

And when you had the amp turned up? It was dropping down that low in the front or in the back? And was the car at idle or revved a bit? How long did it take of playing it for it to drop down to 11.2V?

What car is this? That SAZ is a pretty large amp, capable of drawing a good amount of amperage, over 300A. Depending on your car, you may only have 100 or so amps overhead. Your car may require about 50A-ish, and that alt may only produce 150-170A at idle. Do you know what its idle output is?

 

[rlambert02 10+ year member]

it dropped to 11.2 after about 10 seconds, if that, and that read at the rear battery at idle, at about 2k rpm i think i was in the 12's. And i Believe idle is 170 amps

 

[gckless 5,000+ posts]

How are you grounded from rear to front? Frame or dedicated run?

It's possible there's nothing wrong here, you're just seeing how much that big amp can draw.

 

[rlambert02 10+ year member]

Right to the body, i have it grounded on the bolt that holds down the latch for the rear seat, sanded completely down. So the copper ring terminal is sandwiched between the latch and the body. is it better to run the ground from the rear batt to the amp, or my spot to the amp?

 

[gckless 5,000+ posts]

So you have front battery to frame, rear battery to frame, and amp to frame? You should atleast go from rear battery to amp. That latch is on the floor? It may not be the best grounding spot.

 

[rlambert02 10+ year member]

ok so its better to ground the amp from the battery? and tomorrow ill try to take a picture of what im talking about between the body and latch

 

[gckless 5,000+ posts]

How do you have the rest grounded? Front battery to frame, rear battery to frame also?

 

[Chrispy 10+ year member]

A friend of mine surprisingly runs that amp on lower voltage than that no problem. What ohm load are you running that amp at?

EDIT: Does the amp still cut out or are you just trying to keep the voltage from dropping so much?

 

[NASTY08IMPALA 5,000+ posts]

Check ur voltage at the alt ..most of.those mechmans will charge at 15.3

 

[itsblown 10+ year member]

Check ur voltage at the alt ..most of.those mechmans will charge at 15.3

Thats what Im thinking no way should that alt be charging at 13.8, my stock ****** ford focus alt charges higher than 13.8