Hey gang -

Was curious if any of you could help me diagnose a problem that recently arose in my stereo system. I am running a JL 500/5 amplifier off of an Alpine 7894. I am employing a 1 farad line stiffening capacitor, and until yesterday, I couldn't be happier with the sound. Yesterday, however, I turned on my HU, and my amplifier didn't turn on. Argh! That evening, I began testing various connections, etc. Turns out my capacitor, which has a voltage display, was indicating 5.5 volts. I tested the output with my multi-meter, and sure enough, the 5.5 was correct. Voltage from the battery read 14.4, and I have not had any problems starting the car, etc. - It starts without a hint of hesitation. One thing I know The JL amp is that it shuts itself down, and will not start if voltage dips below 10 volts. Is it possible the cap has gone bad? What else could cause such a dramatic voltage drop?

Thanks so much for your help.

 

check the voltage at the hot lead into the cap and compare it to ground.

if it's 5.5 volts, you've got a problem in your wiring. if it's 14.4 V, it's the cap.

are you fused by the battery on your power run? have you checked the fuse?

 

Thanks for the tips -

I haven't yet checked the fuse, because there is some power coming to the cap, and I thought if the fuse had gone, that the voltage reading would be zero... Hmmm. I wonder what could have suddenly gone wrong with my wiring...

I'll double-check tonite...

 

you would think so and so would i, but i have seen otherwise in the past.

 

Ive had this happen before.

FIrst of all, did you ground to the factory honda ground, or you found your own bolt....I have had grounds go bad before....one day it was 14.4, next day it was 2 volts. Check the ground. Next, ditch the cap. As Ive stated before, it is doing more damage than good. Take it off, and try it again, if it sounds good, leave it off. 500 wrms does not need a capacitor.

 

Hey there, NFRs2000NYC -

No, I found my own ground - Nice big bolt underneath the carpeting in the trunk, just under the LH tail light assembly. Took a good bit of 60 grit to the area first, then hooked her up with 4 AWG. I'll double-check that point... Thanks!

Really - Ditch the cap? I was on the fence about getting one in the first place, then I talked to an installer buddy of mine. He was adamant about installing one in my car, so I did. (I figured he had nothing to gain with this piece of advice, since I didn't buy it from him, or have him install it...)

Anyway - Why more harm than good? I realize that it constantly pulling power from the alternator, and may add some strain to it, but so much so that it may cause harm? Not looking to harm anything of course, but is the stock electrical system hardy enough to have fairly loud volume at night without headlight dimming, etc? And I know I should probably just get a stronger alternator if I'm really worried about it, but... I don't know. Can I bother you to once more enlighten the ignorant?

Thanks again!

 

You have a bad connection somewhere. The voltage drops around the circuit plus the voltage drop across the HU should equal the battery voltage. (Kirchoff's law) So if you put a load on the circuit and measure the voltage drop across each wiring segment, fuse, connection etc. you should find the culprit, i.e. an ~8 volt drop somewhere.

 

actually - i've never had headlight dimming w/ the S. the HID's don't take a whole lot of voltage to keep going once they're up... i mostly notice dash lighting dimming, which is right in front of my face and annoying as all getout...
since i've got battery issues already (deep cycling the stock battery = ), i'm going to see if a yellow top helps solve some of my dimming issues...

but yes, i'd start like i mentioned above. check to see if you have voltage loss before or after the cap, then work from there. sparkie's idea is essentially the same...

 

Caps are only necessary if the amplifier struggles to supply the subwoofer with power. So unless you are running a 2000wrms sub, and your gains are set at max, your cap is just a paperweight. I have experimented with caps many times, and found that they do nothing for base systems like we all have. If you have like 4 12"s, then there is a use for it, but for what we all do, does nothing but add more strain to the alternator.

 

Thanks again, guys, for all your input. Turns out it was my amp fuse. It was so weird. The fused looked intact, measured correctly, etc. I switched anyway (per your advice, PJK3), thinking what harm could that do - Now it works. Whatever! I was pretty happy that I did that first, and not taken the time tearing up my install for nothing...

Pursuant to all of your ideas, I have ordered a yellow-top, and will rip out my cap when it arrives. My alternator thanks you, NFR. I'll let you know if I get any dash dimming problems, etc. Not sure what I'm going to do with my capacitor once I pull it out - maybe have some fun dropping wrenches on the terminals?