I’m probably missing something stupid here so I thought someone might be kind enough to point out the thing that I’m not seeing because of how obvious it is. Duh, me.

Problem: Primary speakers occasionally cut in and out at medium volume. With increased volume, problem gets worse (more and longer silence). Problem will sometimes get better if I lower the volume to almost inaudible for a while, as if the amp “cools down”.

I swapped out primary amp three months ago and the problem went away. New amp worked fine since then, but now the problem is returning.

Equipment:
Head Unit = Alpine 9857
New Primary 4 channel Amp = Rockford Fosgate Punch P400-4 in tool well in trunk.
Sub Amp = Alpine mono sub amp behind pass seat to custom sub in boot.
Bass Shaker Amp = I don’t even remember at this point and its tough to get at, in the trunk directly behind the driver’s seat.

Tested so far:
14.4 volts power to the primary amp.
Amp doesn’t feel particularly hot. Neither did the old one when it had this problem.
The subwoofer channels continue to work fine, even when the regular audio cuts out of front and real R&L channels.
The problem is the same using the radio, CD and iPod inputs.

Thoughts?:

Overheating? Seems strange since it happens on cool days too, even with amp completely uncovered and trunk open.

Intermittent Fuse problem?

Wire wear / grounding?

Gremlins???

 

Do you have the internal amp option turned "off" on the head unit?

Have you checked, doubled check all the wiring to make sure it's properly grounded and there's not fraying of wires anywhere? With the right size fuses?

Are you positive the head unit isn't the culprit?

 

The internal amp is off. The fuses are correct, but I might swap them out just in case.

I fear taking the wiring apart since I’ll have to pull the entire interior to do it. Ugh.

Gotta do what I gotta do.

 

Try to measure your voltage when it 'cuts out'. You might find that you're not generating enough voltage, and the amp is cutting out to protect itself. I'd measure the voltage in two places:
--At the Amp connectors.
--At the battery posts.

Voltages should be the same both places. If not, the drop is due to bad wiring/wrong size wiring/lose connection someplace. If the voltages are the same, and you see a voltage drop when the amp cuts out, then you might have an alternator problem, or you might need to install a capacitor or bigger battery.

Good luck.

 

There was a voltage problem with the old amp at the amp connection but I had (incorrectly it seems) thought that it was the AMP that was the issue.

Hmmmmm.

 

I'd guess a bad connection somewhere, possibly a bad fuse that
can't carry adequate current as it heats up.

 

You can disconnect your power cabling to the amp and check the voltage. Do this with using the ground wire to the amp (don't ground to the body). This will definitely tell you if you have a voltage drop in your wiring harness.

Typically for an amp to be the cause of a voltage drop, it needs to pull more current (amps) than the battery/alternator/wiring harness can provide. If you fused your system correctly, this will cause a fuse to melt, before any other damage is done, so I doubt your voltage drop is due to the amp..

Try checking where/how you grounded the amp. Did you ground to a painted surface or to a clean metal surface? This is usually the weak link...

 

Thanks. I did ground it to bare metal and all of the wiring is the same as with the old amp, run through interior, where it’s been ok for about 5 years, but may have begun to wear. Who knows.

I appreciate the tips. I’ll begin by checking voltage as directed and running some fresh wire outside of the car and see if that makes a difference. If so, then (ugh) I’ve got to pull the seats and the rest of the interior out to run new wire. NOOOOoooooo.......!!!!!

 

Okay. After getting some good troubleshooting advice, here and elsewhere, this is what I’ve come up with. BAD GROUND.

That it may be of help for others who are troubleshooting, here is what I came up with.


Car Stereo PROBLEM: After the radio has been operating for a while, the speakers begin to cut out.

When the stereo is first turned on, all speakers work normally at any volume.

The speakers cut in and out, first only every once in a while, then eventually popping back on for about ½ second every second or so.

All four speakers cut in and out at the same time.

Turning the volume up makes the problem worse.

Turning the volume down can help, but not if the problem has already been occurring for a while.

Eventually the speakers cut out completely.

After the stereo is powered off, the speakers work again for a while.

The sub woofer and the bass shakers (on their own amps) never cut out.

When the HU RCA jacks are unplugged from the 4 channel amp and plugged into the bass shakers amp the signal never cuts out.

This happens with all inputs for the HU.

The HU never shows any problems, switching off or blinking or anything.

Power to the 4 channel amp terminals is a steady 14 volts when the amp is powered down.

Power to the 4 channel amp terminals ranges from about 10 volts to about 8.5 volts when the amp is powered running regardless of volume.

Checking + at the amp and – grounded directly to the body = about 14 volts again.

Power at the battery terminals remains at about 14 volts.

The fuse for the amp has been removed and replaced (same fuse) with no change.

The fuse block shows continuity when the fuse is in place.

The 4 channel amp never shows its “TEMP” or “PROTECT” lights.

I’ve tried to isolate them but the problem seems to occur regardless of which speakers are plugged in to the 4 channel amp.

All four speaker wires read at about 4 Ohms resistance.

This happened with my last 4 channel amp. I simply replaced the amp and the problem went away, until now, about 3 months later.

ANSWER: Bad Ground. I should NOT have had a difference in voltage between when the amp was operating and not, nor when I checked the ground against the wiring to the amp and grounding to the body of the car.