Stereo & Electronics - Pretty sure it's a dying battery.. but... sub prob

Everytime I go to turn the key to start, or just run, the sub thumps about 3-4 times and then sounds ok. At first, I assumed a bad ground or positive lead. However, ruled that out. RCAs are run on separate side of car than power wires.

The other night (headlights on), the sub would thump everytime I hit the brakes, came to an idle, or turned on HVAC. The VU meters on the amp are registering a spike when this happens.

Just want to get your guys' opinions before running and getting a battery or a new amp or just guessing through it. Car IS starting ok and that's why I am a little concerned a dead battery might not be the culprit. It's an 800W amp.

what amp brand model is it

ud be amazed how much interference a cheap amp can pick up

what amp brand model is it

ud be amazed how much interference a cheap amp can pick up

It's a cheapy amp for sure... However, ran it in this car for 2 years with no problems. Car sat for 6 months with it uninstalled, and then I moved it to where the back seat was (from the trunk area). So if anything, it's running about 3' less power cable and has a 2' long ground. Less possibility of it getting interference.

I do plan on upgrading soon, however, want to track down this "bug" first.

your new ground probably isn't as good, and/or you're now picking up something through your RCA's.

Does it do the same thing if you disconnect the RCA's from the amp? that'll tell you where the problem is.

your new ground probably isn't as good, and/or you're now picking up something through your RCA's.

Does it do the same thing if you disconnect the RCA's from the amp? that'll tell you where the problem is.

Yep... thought about that on my way home tonight. I pulled the RCAs... no more sounds.

Here's the strange part (as if this all isn't weird). If I turn off the H/U, I get a steady thump thump thump thump coming from the sub *about a second apart*. Seems to be MUCH more prominent when the engine is off (which is what made me think dead battery). The headunit is about 4 months old... This is it here--->
http://images.bestbuy.com/BestBuy_US/images/products/8130/8130738_sa.jpg



I'm not typically a Pioneer fan, but loved the bluetooth idea. :)

I vote goofy amp. Does is stop thumping a few seconds after you turn it off? A friend of mine has a system that does that and I asked the place we bought the amp from and he just said that those amps do that sometimes.

Oh yeah, how's the bluetooth work on that deck? Does your phone ring through the speakers when connected?

Oh yeah, how's the bluetooth work on that deck? Does your phone ring through the speakers when connected?

It mutes the radio... rings... and then you press a button on the headunit for speakerphone through the stereo.

Also, you can play MP3s from your cellphone on it :) I love it!

On another note... did you buy it from Best Buy? Sounds like the guy that sold it was an idiot. Amps shouldn't just start thumping away for no reason and I had had this amp hooked up for a long time with no issues.

Actually, it was the owner of the company. A small, local company. Most of their amps are really good and even that one works well, but it just thumps a few times when you turn it off for some reason. He was just saying that model does that for some reason.

Actually, it was the owner of the company. A small, local company. Most of their amps are really good and even that one works well, but it just thumps a few times when you turn it off for some reason. He was just saying that model does that for some reason.

Well ok... but it's not the problem with mine. It sounds like they need to mod the internal caps on their amps

This is much more severe than discharging caps though. The sub is actually going to almost full excursion and does not stop even after having the headunit off for several minutes. It also doesn't do it when shutting off the car. Only while starting or the other above listed "causes"

is the amp turnin off when the radio turns off

is the amp turnin off when the radio turns off

Nope.. I have it wired to the fuse block... but that's also how I always had it wired up. Heading out to pull the RCAs from the headunit and see if that resolves the problem. If it does, need to replace the HU... if not, then I will attempt to replace/re-route the RCAs.

If THAT doesn't work... don't know what the hell I am going to do.

OK... so traced it down to either A) the H/U is bad or B) it is a bad battery.

I pulled the RCAs from the H/U and no more "thumping". Swapped them to the front channel RCAs and it came back. Swapped to rears and sub outputs with same results.

So not bad RCAs or interference inline with them. Contacted Pioneer and they stated it could be a bad H/U but the fact that all of the pre-amps are shot at the same time might mean to check that the H/U is getting enough voltage.

Reason I came up with the bad battery idea was because several years ago, I read about how the battery helps to further "clean" the AC current from the alternator. When it starts to crap out, it cannot fill in as a pseudo capacitor as well... causing voltage spikes etc.

Going to replace the battery and go from there. Thanks for the input guys!!!

try runnin a wire from a screw on the headunit (aka chassis ground of radio) and to the outter ring of the rcas and see what happens

pioneers are notorious for ground problems

try runnin a wire from a screw on the headunit (aka chassis ground of radio) and to the outter ring of the rcas and see what happens

pioneers are notorious for ground problems


Thanks dude.. sounds like a very logical test...

Well, replaced the battery with a known "good" one and no dice... still does it.

Going to try and use another known good Pioneer H/U to test if it is in fact THAT causing the problem tonight.