I've got a planet audio momonlock amp doing 1000 rms @ 1ohm. It has 3 40 Amp fuses. I have an AC Delco alternator doing 140 Amps. The first day I installed,(3 days ago) it hit real hard, now it is fading out. I know it's a power issue. I spoke to an alternator specialist and he said that for every 1000 watts, there is approx a 70 amp draw. This makes sense but my fuses add up to 120 on the amp. Any ideas if thebig 3 will benfit me? My stock alt. Was maybe 100-120 amps. Could there be too much resistance in my wiring under the hood? I also feel if I put in an extra battery it will put even more strain on the alternator. I need help please.!!!!
ok... Just found out that my car indeed did come with a 140 amp alterntor, which seems wierd to me because it's 3.8 v6. And 140 amp alternator is bigger than my friends suburban,s alternator which has a 5.3 v8 and bigger than my other friends truck.
the 1000w/70A suggestion applies to constant use of power. An amplifier is not close to constant unless you're playing full volume sine waves. Music has a crest factor meaning its peak power is MUCH higher than it's average (rms) power.
Assuming you wired it to 1 ohm and the amp has typical class D efficiency around 75%...
1000/.75 = 1333w required from charging system. 1250/14v = 95A when playing full volume sine waves. It requires no more than 1/3 that much power for full volume music -- most 1/10-1/4. So realistically you're looking at about 30A rms at full volume. Probably 15-20A assuming you don't blast it all the time.
Obviously your 140 should be MORE than enough current. Big 3 wouldn't hurt. There is definitely something weird happening somewhere. I would get a hold of a DMM and start checking voltage at various locations. FWIW - I have a 130A alt with 700w class D and 360w class a/b. My worst problem is minor dimming at high volume. My previous car had a 110A alt and it ran fine in that. Before that it was 75A. Some voltage issues at idle, but ran ok for 2 yrs before the alt finally gave up.
wow thanks for that info. I have just checked voltage at the battery and the average while playing the system full blast is 13.2 - 13.4. The worst drop was 12.9 . This was over a 3 minute period. This is only at the battery and I'm sure checking voltage at amp it would be much lower because resistance in the 4 gauge wiring. The certificatethat came with the amp says that @ 14 volts it gives exactly 1002 watts rms @1 ohm. Am I onto something here or even close?
wow thanks for that info. I have just checked voltage at the battery and the average while playing the system full blast is 13.2 - 13.4. The worst drop was 12.9 . This was over a 3 minute period. This is only at the battery and I'm sure checking voltage at amp it would be much lower because resistance in the 4 gauge wiring. The certificatethat came with the amp says that @ 14 volts it gives exactly 1002 watts rms @1 ohm. Am I onto something here or even close?
Check the voltage at the amp too. You shouldn't see more than a couple tenths drop. Then go back to the battery and rev the engine a little and see if the voltage comes up at all.
if those look normal (around 13) you can pretty much rule out a charging system issue. If you have voltage drop (your dmm says something closer to 12) at the amp it would indicate some resistance in the power wire at some point which might indicate a problem with the fuse(s) or fuse holder(s).
Otherwise - you either have a problem with the amp and/or sub -- or your hearing.
FWIW - I was just looking back at my original reply. I have 1250/13=95A; that should be 1333/14=95A.