Can you really break a capasitor?

J

JasonCzerak

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So, lets get this out in the open. I've never dealt with a car audio capacitor. So I'm confused if mine actually works.

So, in tracing down my rail gauge-surge with loud stereo issue. I decided to go shopping today.

Ultimate Electronics and Best Buy were right next door to each other. So I shopped both places. I found a "returned" 1 farad Rockford Fostgate cap, I talked them down to $99 and decided to give it a shot as it was cheaper then the Stinger equivalent by $30 at this point.

When I opened the package I find that on the positive side there is a large electrical burn/melt. You all know what happens to your wrench when you are wrenching on a hot alternator ;-). the card you use to slow charge the cap wasn't open. So I'm assuming they (previous owner) connected it up and had a shocking moment. LOL

The cap charged per instructions with the slow charge card that your wire up to it. and when I made contact with the electrical system in my truck there was only a tiny arc. good to go right?

However, my problem is not solved, the gauge will bounce to the beat. I'm awaiting nightfall here to see if it has any effect on my headlights as well.

the voltage indicator works as expected. it shows 15.2 at idle. 12.7 after an hour with the truck off when you crack the door open. With the A/C on full blast and the stereo cranked I see no less then 14.6 volts. The voltage gauge on the dash is interesting, it slowly goes down and the moves back up.

I have about 900watts RMS between both amps. Nothing huge.
 
That very possibly could have killed the capacitor. A HVAC shop or be electronics store will be able to test them.

On a side not:

If you want to have some fun take a 500farad capacitor, charge it, then hand it to a friend to put up.

hehe
 
With the stereo cranked up...check the voltage on both sides of the cap.
 
just the opposite way annit? ground the pos and touch the grnd
 
I'd think that unless the dielectric material was burnt up, good connections should make it work.
 
Reversing the polarity on an electrolytic cap will destroy it. Try it with a small one if you want a nice surprise sometime.

Capacitors will wear out with time, but I would doubt that the one in question would be bad due to age.

I used to install car audio systems professionally for a while and I rarely ever saw much benefit from running a cap. Most of the systems that really needed some kind of electrical cushioning gained much more from an aux. battery installation than a cap. In the case of a diesel pickup with two batteries, I would think there would be enough cushioning to not cause too much of an issue. After all, these trucks get whacked with a MUCH larger electrical drain and transients when the grid heaters cycle than a little stereo could likely give it.

Maybe there is something going on with the amp installation causing you troubles?
 
Several of us with big stereo's and CR Cummins motors are experiencing a bad rail pressure surge with the stereo turned up and lights, etc on at night.

I run a pair of blue top Optima's and get the same thing.

I recently removed one of my 4 amps and it's noticably less surge.
 
How are the amps grounded and powered?

It can make a difference depending on where the engine ECU is pulling its power and ground from vs the amps. If ground relocation doesn't help you might be able to alleviate the issues by using some varistors too.
 
Engine ECM takes power from the batteries which are right next to each other in series. Amps run off a single 0/1 gauge wire from the same batteries to a distribution block then 4 gauge to the amps themselves.
All my grounds underhood as well as power from the alternator are upgraded to 0/1 gauge. (standard "big 3" upgrade)
My amps are grounded through the cab floor to the frame of the truck...also 4 gauge wire.
 
You might try moving the amp's power/ground wires to the other battery.

I know it sounds crazy, but I dealt with a lot of MDT electrical systems and electrical problems at my old job. As per the truck and component manufacturers we were working with it was suggested that the sensitive electrical components such as ECUs and the other computerized stuff be as electrically isolated from the high current items like starters, etc. as possible. We would wire things in a criscross pattern so that the entire battery bank was used as a cushion for the transients that would get created. It seemed to work in our application. Maybe it will work here too?

I find this issue somewhat interesting, as there really should be sufficient protection designed into the major electrical components such as the engine ECU. Cummins, their supplier, or both should be testing for this kind of thing but then again aftermarket installations of components that aren't necessarily meant to be there are out of their control too.
 
Friend of mine who does electrical engineering for the Ram trucks told me all I need to do is ground to the cab and from the hyrdoframe to the battery and I should be good to go in a dodge 3rd gen application.

I forgot the frame to the battery bit at first and has some funky "no bus" errors and a stalled truck. :) So I know my grounding is good now.

So, it's nightfall and I did some testing. No more head light dimming. no more gauge cluster dimming. However, I do have autometer and diprocol gauge dimming.....(all on the same main feed) If I recall correctly, it does require a bit more volume and the dimm isn't as much. tomorrow night I'll compare back to back with the cap pluged in and un-plugged.

We did take the truck for about 40 minute of driving a short while ago right after I installed the cap. Prior to the trip the cap registered 15 volts.. now, with everything off but the motor, 14.7-14.8. I'm assuming everything is fully charged now or something?

Unbroken, I think I've made a connection here. Something I'm going to investigate. The circuit I'm drawing power from for the gauges is one of the fues the TST and Edge boxes used so they can have power during motor start. In the winter time the motor would turn of slowly enough that you could see the rail pressure build slowly from 3K-4K-5K and then the motor fires.. :) I believe i was told by tech support to move the power source into the fuse box to try to fix the gauge from getting "out of wack". This include the backlights in my case as well. I'm running an autometer dimmer for the LED's as well.

I have the gauges on a switch so if I have time tomorrow morning I'll move the feed to the batter terminal


duuuurrr
 
Last edited:
mondtster said:
You might try moving the amp's power/ground wires to the other battery.

I know it sounds crazy, but I dealt with a lot of MDT electrical systems and electrical problems at my old job. As per the truck and component manufacturers we were working with it was suggested that the sensitive electrical components such as ECUs and the other computerized stuff be as electrically isolated from the high current items like starters, etc. as possible. We would wire things in a criscross pattern so that the entire battery bank was used as a cushion for the transients that would get created. It seemed to work in our application. Maybe it will work here too?

I find this issue somewhat interesting, as there really should be sufficient protection designed into the major electrical components such as the engine ECU. Cummins, their supplier, or both should be testing for this kind of thing but then again aftermarket installations of components that aren't necessarily meant to be there are out of their control too.
Click to expand...

In a dodge application, the grids are feed from the passenger side. the starter however is on the drivers side. The main fuse box is from the drivers side. I forgot what other feed is on the passenger side. I've put my stereo on the passenger side for 2 reasons, less "crap" on the battery as my fuel pump and air pump draw from the drivers side already and the ECU isn't on that battery.

As far as the problem unbroken and I have, I think it may be a bug in the gauge. Unbroken, correct me if I'm speaking for you and it's incorrect for your truck. however, if I unplug the rail gauge from the rail harness. I naturally can't see the pressure bouncing, but I can no longer induce a surge while driving and the volume up. So, my thinking here is somehow, when the stereo draws voltage, somehow the gauge mucks with the voltage in the line that it's merely "monitoring". I can't explain it. anything other then checking voltage and some basic ohms and installing these stereo's, i'm clueless. :)


unbroken, can you please give me a pointer here as to how exactly I should monitor voltage on both sides of the cap? I'm confused here a little.


Unbroken, your batteries are in series? As in, 2 6volt batteries?
 
JasonCzerak said:
Friend of mine who does electrical engineering for the Ram trucks told me all I need to do is ground to the cab and from the hyrdoframe to the battery and I should be good to go in a dodge 3rd gen application.

I forgot the frame to the battery bit at first and has some funky "no bus" errors and a stalled truck. :) So I know my grounding is good now.
Click to expand...

Not properly grounding the body/frame and grounding the amps to the body was probably the biggest issue I saw when installing. I was going to ask about this too, but it sounds like you have it covered.
 
JasonCzerak said:
As far as the problem unbroken and I have, I think it may be a bug in the gauge. Unbroken, correct me if I'm speaking for you and it's incorrect for your truck. however, if I unplug the rail gauge from the rail harness. I naturally can't see the pressure bouncing, but I can no longer induce a surge while driving and the volume up. So, my thinking here is somehow, when the stereo draws voltage, somehow the gauge mucks with the voltage in the line that it's merely "monitoring". I can't explain it. anything other then checking voltage and some basic ohms and installing these stereo's, i'm clueless. :)
Click to expand...

I think you posted this response while I was typing my last one.

So, you two are using a gauge to monitor your rail pressure? Do you have an alternative method of monitoring rail pressure available to you? Something like Cummins Insite would be nice to see what the ECU is actually seeing for rail pressure vs. what your gauge is telling you.
 
Get out your multimeter and with the cap unhooked measure for "AC" directly between + and - on your amp, or amp's....the lower you can get that the better. Now hook up your cap/cap's , and it should be located as close to the amp as you can, big wires, big wires, big wires.

Now measure "AC" should be quite a bit less.

Gota say though, never would have taken a returned cap. Like said before hook them up backwards and they are ruined in short order.

Measure around looking for "AC" while the amp is putting out, thats were your greif will be coming from.
 
Joe,

getting to the amp terminals is going to require me taking out the seats again. so it'll be a day when I have some time.

As far as my moving of the gauge lead. they are directly attached to the driver's side battery. Same issue. I didn't notice any real surge on my drive in tho. I need to get on flatter ground then my morning commute with less traffic to be sure.

anyone know of a scan tool that can read the rail pressure. is there anything I can buy from the local autoparts depot?
 
You should really never run the ground for an amp to the battery. The shorter the better. In my setup, I have 4 gauge from the amp to the distro block. From there, its 1 gauge to a seat bolt. The wire run is less than 30".

As to why there were burn marks on the cap, my guess is the method of charging. You can use a resistor, but they get damn hot. I use a 194 bulb. Before you connect battery +, take one leg of the bulb and connect it to battery hot. Then connect the other leg to the lug that will be connected to battery hot. When the bulb is out, the cap is charged. Just connecting power without charging causes the cap (and the ones in the amps) to surge and you get the big ole' spark. It can be hard on a cap not to mention causing you to crap your pants from the surprise.
 
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