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I would appreciate any help! :) My subs keep cutting out and cap reads low voltage.

I have been running my system for over a year without incident. It is composed of two, twelve inch Rockford subs, a 700 watt mono block amp also Rockford, a one farad stingray capacitor, four gauge wire throughout, basic signal wires and RCA's. I'm running a Kenwood deck with small pre-amps.
PROBLEM- My subs started to cut out, and I noticed the Cap. would read low voltage when the subs would cut out, I can't remember what voltage they were reading though. I was running a small 60 alternator, and a fair sized Interstate Battery. Fair sized for a Jeep wrangler. I thought this was my problem, so I upgraded my alternator to 110, and battery to the Optima yellow top.
None of my positive power line has any breaks, or cuts, and the insulation is whole, no slits, with no corrosion. I haven't checked my ground, but when I installed, I installed to stay.
What could be causing this problem, I haven't had much time to explore, and I was just wondering what could cause this, whether it be in the wiring in the alternator, to the battery, from the battery? I would appreciate any help :D
 

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Discussion Starter #2
I should also note, that I am also running a 300 watt, four channel amp for two, six and a half speakers, with their own power lines, etc from deck.
 

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If after replacing the alternator and battery you're still getting low voltage then something went wrong with the installation of of those things. I'm guessing something wrong with the alternator.

Test the battery voltage at rest and with the engine running. It should be at least 11 volts at rest and at least 13.5 volts at idle and up to 15 volts at when revving.
 

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Since you've done about everything but check your ground,thats where I would look.
Could be loose crimp,bolt,heat damage,anything.But yes check the voltage.
 

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I had the same issue...turned out to be the main inline fuse at the battery. It looked tight, but the little allen screw that held the fuse down was loose....

Check all your connections. If you have a multi meter - check another loop to make sure the entire car is still running at 14v, if it's not, you're car's not going to last very long before it dies...then it will also pinpoint the issue to your set up. check your voltage at the bat, after the inline fuse, before the cap, after the cap, into the amp, and your ground....
 

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Test the battery voltage at rest and with the engine running. It should be at least 11 volts at rest and at least 13.5 volts at idle and up to 15 volts at when revving.
W/ the car off, test the voltage at the batt. Then test it at the amp's terminals (just be careful not to short from the + terminal to the case of the amp). The 2 measurements should be within .1V of each other. If not, then u've got a wiring issue (probably corrosion or a loose connection). If the measurements are close, continue testing.

Now, leaving the engine off, crank up some bass just to the point where it's cutting out (test tones would be good here). Test at the batt and at the amp. If the voltage reading at the amp is more that about .5V-1V lower than at the batt, then u have a wiring problem. If the readings are closer than that, u've reached the limit of the batt's capacity (which may be lower than normal if the batt is reaching the end of its life). Of course that shouldn't apply w/ a new batt and alt, but I'm just covering the bases.

Keep in mind that a wiring issue includes the amp's ground the body, but also from the body to the - terminal of the batt.
 
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