New Alternator, Lights Still Dim.... Please Advise

[ronjon228 10+ year member]

Well It starts like this. A couple weeks ago I got a new amp for basically nothing. So Im all stoked. I hook it up, replacing my trusty 2150X MTX and fire up the car. Listen for a while, everything sounds great. So I go to bed thinking happy thoughts. Then I get up, hop in the ride, and crank it up on the way to work. Again, its all good. Then on the way home, the ugly monster rears it head. DIMMAGE!!! I have NO idea why this amp is draining my power. I have a BRAND NEW alternator and its rated at 105amps. I'm using 4 gauge wire from the battery and frame (ground) to my distribution block, then 8 gauge to my 2 amps (not more than 2 feet long). The amp is a PPI PC2600 that puts out 600wrms @ 4ohms mono. I can think of 2 things that could be causing the problem and beyond that Im stumped. First thing, my battery is one of the "stealth" kind thats covered. So instead of the power being hooked directly to the battery its hooked to that seperated post, if you know what I mean. Secondly, my battery itself is from my older car. I am using it because its a larger battery and I figured it may help. However, I think it may in fact be going bad because my car wouldn't start just yesterday. The fact that it was 2 degrees out (F) didnt help but it still made me think. If any of you have any ideas on what to do including a new battery, rewiring, caps, whatever, please let me know.

Thanks

Ron Jon

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[avistar23 10+ year member]

What the amperage draw on those amps ?

 

[ronjon228 10+ year member]

Amperage draw per spec sheet is 80amps. I have an 80amp fuse as well right at the battery. Also, the dimming doesn't seem to follow normal rules. Most of the time you'll get dimming and voltage drops pretty consistently depending on the freq. Real low drops will draw more, while quick bursts will draw less. However, my lights dim really badly for a split second, then go right back up to par. Its like its getting a really quick, hard drain, then it catches up. Any ideas would really help me out. I didnt think this amp really could draw 80amps being that its only 600rms, but I could even be mistaken about that. And 80 amps on my alternator with all the others running (lights, heat, etc.) I can see how that would cause problems. Now Im rambling so I'll stop...

Lates

Ron Jon

 

[ronjon228 10+ year member]

Hrmm... do you think a yellow top would help me out in this instance? You can get em for almost as cheap as a friggin oem battery. From what I've read I realize that my amp should be draining no where near the amount of power to stress my alternator. Also from what I read running a yellow top would solve my problems =) I do have a question though. What advantage, if any, would I have for getting an OEM battery and then running the yellow top in parallel with that. Couldn't I just get the yellow top and use it for everything?

Thanks'

Ron Jon

 

[BDIDDY 10+ year member]

Yellow tops are dry cell (?) and they are made for being drained down and recharged. If your battery is old and it has been recharged often that would probably be you problem.

 

[mulisharider10 10+ year member]

or the fact u r running two amps, the rated amerige on the aftermarke alt says 105 mps at what rmp? that is the question. sure the 2 amps arnt all the much to power, but u r still running 2 and that is like well over 100 amp draw. my suggestion woud be to get the alt. tested to see what it puts out, and if comes close to the rated power, then get a stiffining cap, but dont ony wire it to the sub amp, wire it in befor the distru. block and then both the amps will get the extre bursts.

 

[helotaxi 5,000+ posts]

The amp may only draw 80 amps RMS, but it will draw considerably more than that during music transients which is the dimming you are describing. Also your 105 amp alternator has to keep the car running, including your headlights which are probably drawing 20 amps by themselves, not to mention firing the sparkplugs, running the gauge cluster, powering the headunit, running the blower in your heater in addition to powering the amp. See where I'm going with this? The alt might be enough to run your stereo system if that was the only load on it but it isn't. You need a bigger alt.

 

[avistar23 10+ year member]

The amp may only draw 80 amps RMS, but it will draw considerably more than that during music transients which is the dimming you are describing. Also your 105 amp alternator has to keep the car running, including your headlights which are probably drawing 20 amps by themselves, not to mention firing the sparkplugs, running the gauge cluster, powering the headunit, running the blower in your heater in addition to powering the amp. See where I'm going with this? The alt might be enough to run your stereo system if that was the only load on it but it isn't. You need a bigger alt.

that just about hits the nail on the head

 

[BDIDDY 10+ year member]

The amp may only draw 80 amps RMS, but it will draw considerably more than that during music transients which is the dimming you are describing. Also your 105 amp alternator has to keep the car running, including your headlights which are probably drawing 20 amps by themselves, not to mention firing the sparkplugs, running the gauge cluster, powering the headunit, running the blower in your heater in addition to powering the amp. See where I'm going with this? The alt might be enough to run your stereo system if that was the only load on it but it isn't. You need a bigger alt.

How can it draw considerably more but not blow the 80 amp fuse? :thumbsdow

 

[helotaxi 5,000+ posts]

The power surge is shorter than the blow time of the fuse. Even a quick blow fuse takes close to half a sec to blow at its rated amperage. I'm sure if you looked hard enough you could find the specs for ANL fuses and what their blow time is.

 

[ronjon228 10+ year member]

Allright, thanks guys. The thing about having 2 amps however, it did this before I put in my 4-channel. I honestly didnt see it get any worse when I put in my 4-channel but who knows. So basically you all are suggesting a ho alternator or if Im only short by a small number of amps, getting a cap?

 

[helotaxi 5,000+ posts]

I would say you are short by a significant number of amps with the system cranked and the headlights on. Your car, with the lights on is probably pulling somewhere in the neighborhood of 40 or more amps. Crank the system up really good and the two amps are probably pulling 60-80 amps continuous with peaks putting it somwhere near 100-120 or more. Add that to the load from the car itself and you are looking at somewhere near a 100-120 cont. with peaks of around 140-160. You need a new alt. You can get it on your terms or you can wait till this one dies.

 

[BDIDDY 10+ year member]

I would say you are short by a significant number of amps with the system cranked and the headlights on. Your car, with the lights on is probably pulling somewhere in the neighborhood of 40 or more amps. Crank the system up really good and the two amps are probably pulling 60-80 amps continuous with peaks putting it somwhere near 100-120 or more. Add that to the load from the car itself and you are looking at somewhere near a 100-120 cont. with peaks of around 140-160. You need a new alt. You can get it on your terms or you can wait till this one dies.

It won't die, I have my 81000d on 2 ohms and it has a 175 amp fuse with it, plus I am running a MTX 152 also. Add in all the car's accesories, neons, I guess I am pulling 225 amps or so on a stock 1984 cutlass alt..... wow.

I would have to disagree. The number of amps you are pulling depends on ohm load, the ohm load is never what you have it wired to. That depends on frequency the amp is pushing out, so on so forth.

 

[maylar 10+ year member]

My suggestion would be to track down the source of the problem using an analog voltmeter (VOM) or even a test light.

Crank the system and make the headlights dim with music, then measure directly across the alternator (output stud to case). If the indicator fluctuates the same as the headlights, your new alternator *****.

If it's OK there, then move down the wiring path until you find out where the voltage drop is comming from. You may just have a bad connection somewhere that's introducing losses.

 

[ronjon228 10+ year member]

Ok, Im thinking my voltage drop is on the battery, either the battery is dying on me or the connection of the power wire on the battery is no good. So I ordered a top post connector for my power wire. Also, Im running 4 gauge wire as of now. Do you think I should upgrade to 2 gauge? Now that Im running 2 amps I suppose it couldn't hurt and its not all that expensive (20 ft on ebay for 20 bucks). Also, how should I run my ground wire? Right now its grounded to the chassis. Its not running to the battery at all. As I didn't wire the original install I was thinking about 2 things. I want to make the ground shorter and reground it inside the trunk. And also, should I run a secondary ground up to the battery? Well let me know what you all think.

Thanks

Ron Jon