2003 Infiniti M45 72,000 miles on the clock
JL 600w Amplifier with 2 10" JL Subs, amp requires 60amp fuse, alternator is rated at 110amps, gain is only up halfway.
4awg cable for positive and negative terminals, ground from amp is bolted to frame with clean contact to metal.

I installed this system (and countless other ones on previous vehicles) about 1 year ago. It sounds great, kicks hard, and is linked to the OEM system with a JL Bluetooth receiver. The system ran flawlessly until recently.

Currently, when the system is ran at moderate levels (lets say half way) the car runs and acts normal, nothing out of the ordinary. Then when the volume exceeds the 3/4 mark I start getting some very odd problems. Every time the bass hits hard the car bogs down just for the split second when the amplifier is working during the bass hit. This is most noticeable when cruising between 20-45mph. Once I hit highway cruising speeds their is no noticeable effect. Also when taking off from a start the transmission really slams into gear from 1st to 2nd and slightly less of a jerk from 2nd to 3rd. But once you turn the volume back to the 1/2 way mark the car runs and drives normally.

What's so crazy is that the RPM gauge doesn't even budge during idle speeds or cruising. It just stays straight as an arrow so it seems to me its a lack of power to the transmission and not the motor if that sounds right?

Things I have tried:
Cleaning battery terminals/tightening them (strictly at the battery itself and the amplifier ground)
Replacing battery, which seemed to solve the problem for a few runs but then it came back again.
Haven't had the alternator load tested yet but I did hook it up to a volt tester and I am getting 14.3v when car is at idle.

Question about alternators: Can an alternator provide the appropriate voltage but not provide its rated amperage or do these go hand in hand?

Also the lights are beginning to dim during the bass hits and they didn't previously.

What you guys think? Alternator? Bad ground? Bad amplifier? (I sell JL audio equipment so I could possibly swap out the amp to see if that's the problem)

I tried doing various google searches on this related topic but really came up with nothing that directly correlated with my specific issue. Any help would be great! Thanks in advance.

Maybe you need a storage capacitor for reserve power to the amp during heavy loads? I'm not into car audio, (home audio is one of my hobbies), but I know my friends son was into it for a while and he always had a huge cap for the amp. Huge as in 1 farad.

Could be the start of an alternator showing diminishing returns, but I'd definitely, regardless of the issue, install a capacitor as stated above. Actually surprised you don't already have one considering you sell car audio (unless that detail was omitted). I'm sure you know how they work, but for the purpose of anyone searching the forums, a capacitor stores power and then delivers it upon request to whatever device needs it (in this case a car audio amplifier). It is installed in line with the amp...meaning battery power cable -> capacitor -> amp power port. This in turn allows the amp to pull power from the cap instead of the car on big bass hits or at max draw (high volume). More than likely it'll fix the OP's issue.

I haven't had a car system in a while (although I do have plans to install a smaller sub in this car at some point), but I always ran a cap. Just seemed like a good thing to do.

You need a capacitors for your sub amp.

Do not put a capacitor in. It is a waste and most lilely will not resolve your issue UNLESS you are listening to truely dynamic music. You will be better off getting a backup small agm battery for your trunk, or upgrading your alternator(my suggestion if one is available for this car)...and since you sell this stuff I guess you know this already. I'm having a slightly similar issue with my system right now, havent had time to do any tests.

Do you have any science of them being a waste, TDot? They work much the same as they do in other electronics (in my case, motherboards, since I'm an IT engineer)...and they definitely DO have a purpose.

Before I get into that here is car audio 101. When having power issues you upgrade in the following order.

1/ upgrade battery ground, alternator ground, and power wire from alternator to battery.
2/ upgrade main battery to faster discharge. The cars battery was never designed for this type of stuff, which is why there is a dedicated aftermarket for car audio batteries.
3/ upgrade alternator.
4/ add second battery (don't do this first even though I previously said that)
5/ add cap depending on type of music, and if you really need to do this, you most likely have not done something else properly.

Your system alone is pulling roughly 50 amps (how much you're actually using, I don't know). I don't think there is enough headroom on our alternator for that, thats why the faster you drive the faster the battery replenishes and is able to provide the reserve smoothly.

What works for one application does not necessarily work for another one. Motherboard does not equal car. What is the reason for a cap? To provide power for a depleted system. Why do MOST people, and what I would say is the original reason, people put caps in their car? To stop their lights from dimming from the amp draw. So then why put the cap on the amp instead of the lights? What the cap does is release its stored energy to supply the demand, then it recharges. Release...recharge...release...recharge...release...recharge. If you are playing the type of music that "needs" to be played loud, at what point does a cap actually have time to recharge after depletion? BOOM, BOOM, BOOM, BOOM, BOOM. Where is the quiet portion of that music to recharge? Because I'm sure he's not banging opera. You are still putting a strain on the alternator and battery with a cap. Remember the type of music that was running when caps were introduced to car audio, it's not the same as today...in production, engineering, or dynamics. Take a pale of water, cut a 3 inch hole at the bottom, and fill the pale with a 1 inch diameter hose. Whats eventually going to happen? That is your cap. A cap eventually becomes a bottleneck.

Remember, for the most part your battery is your cap when the car is running. So if your battery cant handle the load, how is a cap going to handle it? And remember you aren't even talking about dimming lights at this point. A cap for car audio IS a waste, and I stand by that.

I'm glad you asked me this to make me go through the motions, I can go ahead and fix my problem now.

TDot wrote: ......Remember, for the most part your battery is your cap when the car is running. So if your battery cant handle the load, how is a cap going to handle it? And remember you aren't even talking about dimming lights at this point. A cap for car audio IS a waste, and I stand by that.

Very well said!

In the old days, before alternators came along (TY Chrysler), generators were the norm. Generators were very poor at charging at idle, especially under load, ignition, lights, A/C, etc. They were fine once you picked up RPM; then they were able to replenish the battery as needed. The system worked because the amps you needed to keep everything running at low RPM was provided by your battery amp reserve. Once you got moving, the generator replenished the battery charge.
Cars had an ammeter on the dash, so you could monitor states of charge & discharge..
Ah, the good old days!

Of course, the methods of diagnosing & testing charging system components have changed as the technology has.
However, what has not changed in diagnosing & testing for over 80 years is the lead acid battery.
Also, (then as now), it is the first item you must be absolutely sure is up to snuff before proceeding with other components to track down root cause failures, (if it was not the battery itself)!

TDot wrote:Before I get into that here is car audio 101. When having power issues you upgrade in the following order.

1/ upgrade battery ground, alternator ground, and power wire from alternator to battery.
2/ upgrade main battery to faster discharge. The cars battery was never designed for this type of stuff, which is why there is a dedicated aftermarket for car audio batteries.
3/ upgrade alternator.
4/ add second battery (don't do this first even though I previously said that)
5/ add cap depending on type of music, and if you really need to do this, you most likely have not done something else properly.

Your system alone is pulling roughly 50 amps (how much you're actually using, I don't know). I don't think there is enough headroom on our alternator for that, thats why the faster you drive the faster the battery replenishes and is able to provide the reserve smoothly.

What works for one application does not necessarily work for another one. Motherboard does not equal car. What is the reason for a cap? To provide power for a depleted system. Why do MOST people, and what I would say is the original reason, people put caps in their car? To stop their lights from dimming from the amp draw. So then why put the cap on the amp instead of the lights? What the cap does is release its stored energy to supply the demand, then it recharges. Release...recharge...release...recharge...release...recharge. If you are playing the type of music that "needs" to be played loud, at what point does a cap actually have time to recharge after depletion? BOOM, BOOM, BOOM, BOOM, BOOM. Where is the quiet portion of that music to recharge? Because I'm sure he's not banging opera. You are still putting a strain on the alternator and battery with a cap. Remember the type of music that was running when caps were introduced to car audio, it's not the same as today...in production, engineering, or dynamics. Take a pale of water, cut a 3 inch hole at the bottom, and fill the pale with a 1 inch diameter hose. Whats eventually going to happen? That is your cap. A cap eventually becomes a bottleneck.

Remember, for the most part your battery is your cap when the car is running. So if your battery cant handle the load, how is a cap going to handle it? And remember you aren't even talking about dimming lights at this point. A cap for car audio IS a waste, and I stand by that.

I'm glad you asked me this to make me go through the motions, I can go ahead and fix my problem now.

Interesting post and I can understand that side of the coin. I guess we assumed he did 1 and maybe 2 from your list considering he sells audio...I've hardly ever heard of anyone adding a second battery or upgrading the alternator for a regular sound system (not some crazy competition-level sound system). I know that in my previous experience (mid-2000's) that I did NOT upgrade my battery and did NOT upgrade my alternator. I just made sure my wiring was top notch (gauge, length, etc.) and added a cap and I never had any issues with draw and I had some pretty decent systems.

Perhaps due to music changing that's no longer applicable, you may have a point. I haven't had an aftermarket system in like 7-8 years.

Upgraded to a higher discharge rate battery does the exact same thing a capacitor would do.

I have installed caps in the past with little to no results. They did produce a slightly tighter initial "thump" but they never resolved dimming lights.
I have 4awg wire which well exceeds that amount of amp draw for an 18' run so upgrading cable would be a waste. Like I said in the initial post the car operated normally for almost a year until this issue came about so that tells me that something is failing as far as an electrical component on the vehicle. When I replaced the battery it did go away for a short duration so I am guessing it has to be an alternator issue now or a grounding issue for something besides the stereo grounding points. I do not get any warning lights and the car isn't throwing any codes from any of this so its just mind boggling.

Does the transmission have a ground that could be failing? Any idea where to locate it? Looking in the service manual the grounds are so vague and the pictures displaying the location show you little to nothing.

Thanks for the responses.

I agree that Caps for the most part can be a waste. their job is to supply additional voltage whenever the big draws occur, aka heavy bass hits. and if you listen to super bass heavy songs, it will just stay drained leaving it pointless. Also, If you have a weak electrical system, the capacitor will never stay charged like it should. like it was stated earlier you need to do whats called the big 3 upgrade. increase your wiring size from alternator to the battery, main ground to the battery, and ground to alternator. this will make a substantial difference. once you do that, install a better battery. If your JL amp is the one with the RIPS system that will play 600 watts regardless of ohm rating beware, they are VERY power hungry. I ran a 500/1 and a 300/4 in my Tacoma, headlights would significantly dim even at moderate volumes. I then swapped both out for an audison Voce 5.1k 1600 watts RMS amp (twice as much power) and did the Big 3 upgrade. now the lights only dim when its full blast and on certain songs.

SL33P3RM45
how did you wire up the JL stereo? I am interested in installing an aftermarket head unit where the cassette deck is in my 03. I plan just pushing the cassette up into the dash and modifying the existing whole / space to accommodate the new single din head unit.

bent99 wrote: ↑

Thu Apr 06, 2017 4:18 pm

SL33P3RM45
how did you wire up the JL stereo? I am interested in installing an aftermarket head unit where the cassette deck is in my 03. I plan just pushing the cassette up into the dash and modifying the existing whole / space to accommodate the new single din head unit.

Did you ever do the install? I am thinking of doing the same thing.

I never got the chance. Upgraded to a Gray 04 (black leather, dark wood, 95k, so nice) last June and then hit a dear in September on my way to College Station to see my son. Stupid aggie deer. Sorry to say I bailed on the brand and went Lexus IS350. Happy with the car but miss the V8 rumble.