testing battery / alternator

[robr]

what is the best way to test these components. they seem to be fine until......

well, i just installed a 4 channel amp, 2 channels are for the subwoofer and what happens is even on the very lowest volume, on a bass hit, voltage at the amp drops from around 12.5v to 10, those two channels shut down, voltage climbs back to 12, channels kick back on, sub goes "BLARP", and the process starts all over.

I'm running 4ga power direct to the battery, I had grounded the 4ga ground to the seat, but I'm now told aluminum is a crappy conductor and that it should be grounded back to the battery (which is where I had 8ga power and ground to start with the same problem, but the amp manufacturer told me I have to use 4, while someone else told me my ground run was too long).

I know it's not the amp or the sub, those have been tested and replaced and the problem still occurs, so it HAS to be ground, battery or alternator. Ground I can't test without running (and purchasing) more wire (it's going to be impossible to fit two 4ga thru the hole in the firewall under the stock sub location so I'm not sure what I'm going to do here so I figured I'd test the other two first). Is alternator just a simple volt meter test across a couple of terminals somewhere?

 

[NSX TT]

Originally posted by robr:
what is the best way to test these components. they seem to be fine until......

I'd test the other two first). Is alternator just a simple volt meter test across a couple of terminals somewhere?

To test the alternator just get a voltimeter and plug to each side of the battery terminals so you can see the read out.of course the car must be runing.to test the battery you should put a load on the battery with one battery tester to see how much volt the battery will hold, when is under load,it should go lower than 12 volts.this test is with the car shut off.well good luck and I hope this will help.
Armando

 

[NSX TT]

Originally posted by NSX TT:

Originally posted by robr:
what is the best way to test these components. they seem to be fine until......

I'd test the other two first). Is alternator just a simple volt meter test across a couple of terminals somewhere?

To test the alternator just get a voltimeter and plug to each side of the battery terminals so you can see the read out.of course the car must be runing.to test the battery you should put a load on the battery with one battery tester to see how much volt the battery will hold, when is under load,it should not go lower than 12 volts.this test is with the car shut off.well good luck and I hope this will help.
Armando

note:should not go under 12 volts

 

[NyC NsX]

make sure that the ground from the battery is also a 4 gauge cable to the body of the car and check what the map rating of the alternator is ...maybe you need a high output alternator. For voltage drops you can steady them out by installing a power capacitor. One more thing...you can also change the battery to a low resistance capacitor type aka optima battery.......good luck i hope this helps

 

[robr]

thanks but we are no where near where a cap or high output alternator is necessary. its just a simple 50x2, 200x1 amp and the voltage is sagging with all gains turned almost off.

power and ground is 4ga and i wired the ground straight to the battery tonight instead of to a seat bolt just to make sure the ground was good. so, with 4ga power and ground wired direct to battery, all gains turned almost off, voltage is dropping to 10v on bass hits. something is just plain whacked.

i just want to make sure i'm 100% sure whether its the battery (unlikely) or alternator (more likely given the symptoms) before i consider replacing one. everything else in the vehicle works 100% and this is the first sign of anything wrong ive seen.

 

[Kinan]

Take a jumper cable and duplicate the ground connection from the battery to the amp ground. If the voltage goes up at the amp, you know the ground path is bad.
If not, repeat for the positive path.
When you find the bad path, it will be one or the other, Take a voltmeter and measure across every one of your connections while the amp is on and repeating its failure.
You will find the bad/loose connection by measuring a high voltage drop across it. Say greater than a few 1/10's of a volt.

 

[robr]

unfortunately i dont think thats an issue. there are only two wires, they run directly from the battery to the amp, and one is fused, so there is a break there. however, this is all new wiring, i completely replaced the old wiring thinking there might be an issue. man, this is crazy!

 

[robr]

im so stumped. alternator measures 14.54V out, when i connect the sub to the amp, the amp voltage drops to 10v, but the alternator stays at 14.4x-14.5x.

i guess next step is measure voltage at the battery, i should have done that while i was out there but i just thought of it.

 

[NSX TT]

i guess next step is measure voltage at the battery, i should have done that while i was out there but i just thought of it. [/B][/QUOTE]

I guess that's what you should had have done before anything else.

 

[robr]

i was just under the impression that while the car was running, everything was being powered by the alternator rather than the battery, so that made the alternator more of a suspect, unless i misunderstand.

 

[mandrewz]

I am about to do an install my self, so I am very interested in your problem. I was buying an amp hookup kit (8 guage-for a 300w
amp), and the salesman was very disappointed that I was not buying a capacitor as well. He said the NSX was very particular about voltage from their past install experience, but since this was at Circut City, I ignored his request. I am baffled by electronic details and lingo, but he claimed the voltage regulator would be upset by an aftermarket systems differnt from stock demands, however the Dali/Goldenears system makes no mention of needing a capacitor with it's greater power requirements. Please keep us informed. Are you using the stock headunit, or aftermarket?

[This message has been edited by mandrewz (edited 09 August 2002).]

 

[robr]

the NSX should need nothing special. there is nothing special about the charging system, heck its probably the same as the accord .

however, i am doubly confounded now, i checked battery voltage, it dipped from about 12.5v down to 11.9v on bass hits (again quiet, gains turned down). should have been fine, even pulled up my fiances car and jumpered her battery to mine.

at this point the only explanation i have is that i have two bad brand new amps with identical problems

.

 

[BryanZublin]

Originally posted by robr:
(snip) I'm running 4ga power direct to the battery, I had grounded the 4ga ground to the seat, but I'm now told aluminum is a crappy conductor and that it should be grounded back to the battery (which is where I had 8ga power and ground to start with the same problem, but the amp manufacturer told me I have to use 4, while someone else told me my ground run was too long). (snip)

Aluminum is actually a pretty good conductor compared to iron (steel). In any case, I'd use large conductor copper cable for both power and ground between the amp and battery (which I think is what you have already done). The battery can supply much higher current for short durations compared to the alternator. To ensure an accurate measurement at the battery, be sure both volt meter leads are touching the battery posts (do not use the chassis for the negative lead).
Bryan Zublin

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Zublin Engineering
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