Stereo Amp Power Draw?

terraform · Aug 8, 2005

Hi,

I bought my car a few months back. The previous owner had installed what I considered to be way too big of an amp/sub combo in the car. It's a Jensen 600 watt amp and 2x12 subs. Anyway, I've been having some trouble with the charging system, as the car does not like to start sometimes. For some reason, this is usually right after it's been driven for some amount of time. I thought this was the starter initially, but someone jumped the car once when it wouldn't turn over, and it worked.

So, on to the electrical system. The car has a new(er) battery and a new(er) replacement OEM altenater. Also, it has the stock pulley system and the battery does accept a charge when I hook a battery charger up to it.

OK, now all that's out of the way. Now for the real question. I decided to check the amp settings (since, like I said, this is alot more bass than I need) and I found that virtually everything related to output level was maxed out. So, I set the output level to about midway and turned off the bass boost, in hopes that this would conserve some power and perhaps give the altenator an advantage over this big amp. What I want to know is - is this going to make any difference?

Also, do amps draw the same amount of power regardless of what output level they're set at?

MyEarsHurt · Aug 8, 2005

The system could be wired wrong, are the amps off when the car is off? If not, then that could be a major part of the problem. But as for a big system causing charging problems, you need a lot more than 600 watts to cause any trouble. Could be a bad alternator if its not OEM, like if its just NAPA or something...anyway, good luck.

terraform · Aug 8, 2005

MyEarsHurt said:
The system could be wired wrong, are the amps off when the car is off? If not, then that could be a major part of the problem. But as for a big system causing charging problems, you need a lot more than 600 watts to cause any trouble. Could be a bad alternator if its not OEM, like if its just NAPA or something...anyway, good luck.

Yea it's not on when the car is off. It starts fine when it's cold. It typically has problems turning over after it's been driven for a while (with the stereo on, obviously). It's a Ford brand altenator, a refurb. The system does charge, because I've jumped it and had it charge up again.

The important thing to me right now is to determine if the amp will actually draw less power from the system if the output level is decreased on the amp itself, or if amps just draw a constant amount, regardless of output.

downsouthman1 · Aug 8, 2005

Primarily the system could use a capacitor. Also, with regards with what MyEars eluded to, the remote wire on your deck or amp may not really be tied in to the remote. If it's tied into a continual power line, that means that even when your system appears to be off, it's really on. This will drain the battery but doesn't explain why your car only sometimes has this problem. He is right about the fact that 600 Watts is not enough power to cause this problem. I've been running a system in Mustangs since the Fall of 1999. In every case it's been 1 or 2 500 Watt 12s. In my current case, it's 2 of those with an 800 Watt Amp. I do not, however, have my Gain maxed out. There's no point in that. I have it about half-way but the facorty (MTX) recommends that you keep gain minimized completely.

forpit2000gt · Aug 8, 2005

an amp does not draw as much if it is half way as it does at max. It should not be drawing the battery. do you have a capacitor installed. do the lights dim at night if you are turned up? it does sound like something is wired in wrong.

BooWFO · Aug 9, 2005

Ok try these throw a Multimeter on the car when turned off if voltage starts dropping your drawing current somewhere. Find it the amp SHOULD have a fuse within 18" of the connection at the battery if so pull the fuse and see if that helps. If not you have more trouble and need to spend some time and find what is drawing current.
Although with what you describe it sounds like a bad battery/ alternator. Not up on current charging system but I would check to see if the alternator is charging when car is warmed up and if the voltage is getting to the battery.
A cap will help with the dynamic's of the system but it really won't help at the most it will be a bandaid. IMO.

forpit2000gt · Aug 9, 2005

do you have a test light and do you know how to test for a draw with it?

lgndracer · Aug 9, 2005

downsouthman1 said:
I do not, however, have my Gain maxed out. There's no point in that. I have it about half-way but the facorty (MTX) recommends that you keep gain minimized completely.

Gain is not an "output" adjustment, it is to adjust input sensitivity. Not all decks have the same preamp output voltage, so the gain is used to match the input of the amp to the output of your head unit. If you over gain the amp, you distort the input stage prematurely and end up distorting the the amp by overdriving it.

Torinalth · Aug 9, 2005

I am along the same line of thinking as downsouthman, the power output of 600 watts (and also considering its a jensen) is not going to cause an issue at all. a capacitor will not alleviate the problem either, so dont bother spending the money. as stated earlier, check the amp...

does it have a power on light? does it have a "protect mode" light? can you tell where the amp turn on wire goes (should be a small wire between the power and ground terminals)?

when the car is off, radio off, does the power on light of the amp stay on? if yes then this needs to be addressed as it will slowly drain the power of the battery when the car is off.

if this didnt fix the problem then when the amp is on, does the "protect mode" light come on? if so, then you probably have a wire isssue or possible overdrive of the amp... bring down the gain to about 1/2 and see if it corrects the problem... then check to see that the ground cable from the amp is short (prefered under 1.5 foot in length) and tightly bolted to a solid piece of metal with no paint in the way.

still an issue? then its time to problem solve on a more hands on level... under the hood, remove the inline fuse that goes on the power wire that runs from the battery to the amp. yes this will kill the subwoofer, but this will at least give you a basis of if the issue is bleedoff from the amp or something else.

there are many many things to check with power issues that are amp related.... but hopefully this will give you some things to try. curiously... how often do you have the dead battery problem? once a week, month, 6 months? just curious to know how long it will take for the problem to be figured out using my methods....

Torinalth

terraform · Aug 9, 2005

Torinalth said:
I am along the same line of thinking as downsouthman, the power output of 600 watts (and also considering its a jensen) is not going to cause an issue at all. a capacitor will not alleviate the problem either, so dont bother spending the money. as stated earlier, check the amp...

does it have a power on light? does it have a "protect mode" light? can you tell where the amp turn on wire goes (should be a small wire between the power and ground terminals)?

when the car is off, radio off, does the power on light of the amp stay on? if yes then this needs to be addressed as it will slowly drain the power of the battery when the car is off.

if this didnt fix the problem then when the amp is on, does the "protect mode" light come on? if so, then you probably have a wire isssue or possible overdrive of the amp... bring down the gain to about 1/2 and see if it corrects the problem... then check to see that the ground cable from the amp is short (prefered under 1.5 foot in length) and tightly bolted to a solid piece of metal with no paint in the way.

still an issue? then its time to problem solve on a more hands on level... under the hood, remove the inline fuse that goes on the power wire that runs from the battery to the amp. yes this will kill the subwoofer, but this will at least give you a basis of if the issue is bleedoff from the amp or something else.

there are many many things to check with power issues that are amp related.... but hopefully this will give you some things to try. curiously... how often do you have the dead battery problem? once a week, month, 6 months? just curious to know how long it will take for the problem to be figured out using my methods....

Torinalth

Ok, first off, you guys need to understand that this problem does NOT happen when the car is cold. As in.. the car can sit for a week (which it does quite often) and turn over, no sweat. I really don't think the amp is staying on. The problem only happens after the car has been driven around for a bit, turned off, and then you try to start it immediately after. Which makes me think that it's either the altenator (which would make sense, except the system does charge, and the battery does take a charge when you hook a charger to it) or a problem with the amp putting too much load on the charging system when I'm driving around, and then when the car is turned off, the battery doesn't have enough power to turn the motor over again. I dunno, I'm up for any ideas at this point, but I'm pretty damn sure the amp isn't staying on, so I think we can rule that out.

forpit2000gt · Aug 9, 2005

check your power connections, grounds and positives. May be a temp thing. or could be a bad battery.

BooWFO · Aug 9, 2005

Yes like I said above I have seen from first hand that a heat soaked alter. will cause this kind of problem. It is possible that once heat soaked it is not charging the battery also I assume you checked the alt. leads and the leads goin to the battery to verify it was charging. Have you done it while HOT. I also suggest disconnect the AMP and see if it happens if it does then it is not the AMP but something else. Electrical problems are some of the most time consuming things to track down. Of course most are fairly easy to fix.
You do of course have some basic tools. Such as a Multi meter, screw drivers, sockets and wrenchs, some jumper wires, various wire sizes and connectors.
If in fact your charging system is working (Is the regulator build in to the alt.?) and isn't suffering heat soak. Battery is in fact ok (I don't trust AZ or pepboys) then you have a large draw somewhere that is causing it. I would take the time to find it because that large a draw could cause a fire.
As a side note you are positive it isn't a starter issue correct? I know heat soaked starters will do this also. ie longtubes too close.

terraform · Aug 9, 2005

BooWFO said:
Yes like I said above I have seen from first hand that a heat soaked alter. will cause this kind of problem. It is possible that once heat soaked it is not charging the battery also I assume you checked the alt. leads and the leads goin to the battery to verify it was charging. Have you done it while HOT. I also suggest disconnect the AMP and see if it happens if it does then it is not the AMP but something else. Electrical problems are some of the most time consuming things to track down. Of course most are fairly easy to fix.
You do of course have some basic tools. Such as a Multi meter, screw drivers, sockets and wrenchs, some jumper wires, various wire sizes and connectors.
If in fact your charging system is working (Is the regulator build in to the alt.?) and isn't suffering heat soak. Battery is in fact ok (I don't trust AZ or pepboys) then you have a large draw somewhere that is causing it. I would take the time to find it because that large a draw could cause a fire.
As a side note you are positive it isn't a starter issue correct? I know heat soaked starters will do this also. ie longtubes too close.

It's funny you mentioned this because I initially thought it might be the BBK longtubes on the car causing this. I actually assumed it was this problem until someone tried jumping the car when this happened and it did turn over. Also, typically when it struggles to turn over in situations like this, the clock on the dash resets, so I assumed it wasn't a starter issue. But maybe I'm wrong?

Torinalth · Aug 9, 2005

if the clock resets then it will be battery related, as the constant power line is being dropped between the battery and radio. have you had the bettery tested by a local place reiciently (even though its semi new), could be a freak. if it checks out ok, then i think boowfo has it right.

also, my apologies for not comprehending enough of your post to see the issue was not time related.

Torinalthq

terraform · Aug 9, 2005

Torinalth said:
if the clock resets then it will be battery related, as the constant power line is being dropped between the battery and radio. have you had the bettery tested by a local place reiciently (even though its semi new), could be a freak. if it checks out ok, then i think boowfo has it right.

also, my apologies for not comprehending enough of your post to see the issue was not time related.

Torinalthq

Well the clock thing is odd too.. it's not the clock on the radio (the radio settings stay intact) it's the clock on the dash. Maybe it's not related... seems like it is though. Can't wait to ditch this brick. In the meantime, I gotta make sure it's reliable...

Torinalth · Aug 9, 2005

my one suggestion is still valid though pull the fuse to the amp so its not getting any power and run without for a bit. if you dont get the power issue anymore then its the amp, if not then maybe by then you may prefer without the subwoofer and just remove it... a lighter car is a faster car.

Torinalth

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