Capacitor always on?

It will shut off by itself unless the display is defective.

The cap will never drain your battery because once it is charged it remains "neutral" until it is discharged or in operation.

The capacitor does not shut off, and no it won't drain your battery. A capacitor is used when there is a large drain for a very short period of time like when your bass hits (it is not for a continuous drain on your system if there is too much attached for you alternator to handle).

kymadan wrote:

---

The capacitor does not shut off, and no it won't drain your battery. A capacitor is used when there is a large drain for a very short period of time like when your bass hits (it is not for a continuous drain on your system if there is too much attached for you alternator to handle).

---

Sorry... I need to add to this.... The capacitor does not shut off.... But the light does shut off when the capacitor is idle for a period of time.

Thats what I meant also kymadan if misunderstood.

(it is not for a continuous drain on your system if there is too much attached for you alternator to handle)

If the alternator can't handle the demands of the system a cap won't really help that. The charging system and all wires need to be up to task.

During higher current "bursts" such as heavy bass, the cap is actually meant to make up for any momentary voltage drop in the power wires of the amp,but realistcally, if the wires are the proper gauge or bigger (never can be too big) it is highly doubtful you would notice any difference by ear.

However, noted that this cap is used for asthetics in this case.

You could check with the manufacturer about whether the light should go off or not.. you could also install an ammeter into the circuit and measure how much current the light is drawing.. caps will also 'self discharge' over time.

I would suggest you know what you're doing if you decide to attempt to measure the curent draw.. if the cap is discharged then you might smoke the meter (or the meter fuse) when you try to take the measurement.

Caps.. I personally don't have a problem with them. I don't think it's understood what the actual purpose of them is, and they get the blame for not fixing problems that they don't have the ability to fix. I believe they make a measurable difference, but perhaps not an audible one.

Something I'm seeing more of now that it's getting darker is the inability of the alternator to quickly change output.. there is an inherent lag issue with increasing altenator output with regard to transient loads. I'm noticing this in situations of engine idle and a increased load of AC compresser and condenser fans.. while running defrost, the AC system will cycle.. when the system cycles on, the headlights will momentarily dim, then come back up to their normal brightness as the alternator increases output. If you consider how an alternator/regulator circuit works it's not an unreasonable condition.

Thoughts?

Jim

My personal thoughts on it are as such. I would imagine it would depend on the type of charging system components combined with the alternator that would determine when it "kicks" in. I notice with higher output alternators that they produce lower voltage at idle, but rev it up and I have seen some approach 15 volts.

As far as accessories dimming etc. I have noticed depending on the vehicle that the dash lights and head unit display lights will dim to bass beats. This is without any external amplifiers so my deduction is that it is Vdrop due to the the small gauge wires contributing or completely causing the loss.

IMO I would think that a "stiffening" capacitor is used to deal with this issue, but only for the amplifier(s) but under more extreme conditions..such as high powered amplifiers under heavy current demand (bass notes etc). The sudden "rush" of current is large enough for a brief moment to be resisted by the wire in most cases, causing a Vdrop in the wire, hence less V reaching the amp(s) at that moment.

I can't imagine a cap really doing much else of any purpose such as filtering ripple current or stabilizing voltage when the instability stems from a charging system/battery that is not up to task.

Anyone agree/disagree?

azn, are these voltages measured at idle?

13.8 - 14 is normal for most late model vehicles when running so I would not be too concerned. however on older vehicles I have seen cases where the voltage measurments do not increase very much when running vs. not running, but the vehicle still functions and starts as well as any other.

You state your friends is 14.4. Is the reading from the same DMM?  Are both your explorers the same year and same options?

In my reference to "higher power alternators" I am speaking about a replacement alternator in vehicles where we are using amplifiers that demand current which exceeds the stock alternators rated output. I have noticed that when I take voltage reading at idle, the reading is actually lower then what I read from the stock alternator. Once you bring the rpms up, thats when I get the higher readings.

The thing that I question is this "lag" . You state it happens when you turn on the fan. Mad scientists also mentions this as 'momentaty dim" when condenser fans, defrost is used. Also mentioned is AC compressor. I notice that ac compressors can lower engine rpm (drag) and perhaps that is part of the issue. However most systems also raise the rpm to compensate but I imagine there is a time lag between when the compressor is turned on, to raising the rpm. regardless, the electric blower fan will turn on with the compressor if the HVAC was off to begin with.

I know that electric motors when first turned on basically can act as a short circuit, or very close to it for an instant which is why many vehicles use breakers for things like power windows etc. Now I am wondering since this is the case that perhaps when the motors are first powered up, if the very low resistance when the motor is initially activated is causing a current draw that is exceeding the alternators output for a brief lenght of time. Perhaps even more then the battery can deal with. But once the motors are running I would think the voltage would stabilize not so much by the alternator "kicking in" but as a result of the current draw decreasing once any electric motors are operating. And maybe this 'lag" is simply the amount of time the charging system/battery takes to stabilize. Additional draw is on the wires as well during this period so there may be a few factors that come into play.

Keep in mind this is only a theory and there may be more to this.