How can you tell if a car audio capacitor is bad?
 

Car audio system - 2 550 watt amplifiers, 2 10" subs, 2 250 watt 6x9s, 1 .5 farad capacitor, upgraded battery and alternator. After installing the capacitor according to the manufacturer's wiring diagram, I find that the car battery is draining while parked with the system turned off. The amps are powering off, the only apparent cause is the recently added capacitor. After removing the cap from the system, the battery drain appears to have stopped. Is this normal for a capacitor to drain the battery under these conditions, or could it be malfunctioning?

If the cap is always connected (upstream of the power switch) there will always be a drain.

That cap is essentially a spare battery for your car (that reserves for your audio system). Even if the car is turned off, that thing is charged and draining. Depending on the reserve of the cap, this could determine how much it drains, as well as if your audio system is using the reserve frequently or not.

If you dont, you should 100% put some kind of sign near it letting mechanics, etc. know that even though the car is off, touching that cap will make their hair stand up :). Warning signs are good.

Testing a cap is very simple. Remove it, and measure the voltage across the terminals, which should be about 12V. Wait 10 minutes (time it), and measure again. If the voltage has dropped, there is leakage. The current draw can be calculated as i = C*dV/dt, where dV/dt is the voltage drop divided by time. As an example, a drop of 1V over 10 minutes would be caused by a leakage current of 2.5mA.

Good advice.

You can also look for a parasitic draw right up at the battery. Test with your entire audio system connected properly. If you see a parasitic draw (which you say you will), then disconnect the battery lead running to your audio system and test again. If the draw drops, then you know it's the cap or amps causing your problem. If it doesn't drop, then it's something else in your car causing the problem.

Just a solid method for troubleshooting the entire electrical system in your car.

I had a 1 farad cap go bad once, it blew black liquid all over the rear dash of my car.

Cap = Waste of money.

here we go....

I experimented with caps long ago. I had a cheap hifi amp and I wanted to find out what would happen if I added a large cap. (.5f) into the power supply. I expected it to help in the bass response. Instead, it cleaned up the high range significantly. I would say that caps are worth it.

If you blow one up, you either had it in backward or it was cheaply made.

;) Well, they are. Just a way to get extra money out of the wallets of those who dont know. I can say that I fell for the same craziness. I own 3 caps. I use 1 in my wifes car. Why?? Because I already had it, and it makes a good distribution block. LOL :ylsuper:

Installation of the cap was not my first rodeo.

My cap was definately not wired incorrectly. I even charged the cap with a resistor before final connection to avoid spark (burn mark on cap).

It was in my car for around a year before it popped. The cap was a Stinger 1 farad capacitor. I did get the cap 2nd hand from a pawn shop with some subs that I purchased, so as to what may or may not have happened to it before I got it, I have no idea. I have not owned another capacitor since, and have no future plans of using one.

I found out that my cap was "leaking" because the wires weren't connected very well.. It has a voltage display on it, and I could watch it drop from 12v to 10.5v about .1-.2v per second. I cut the wires back so i was using fresh copper, re connected them and made sure the screws were super tight and it stopped the leak for me.