'89 Acura Legend, did Big 3, need some advice (possible Alt. problems)

[buuzero 10+ year member]

Ok, I posted this in the Big 3 sticky, but I thought I'd post here so more could see it (and possibly throw some advice my way):

I have an '89 Acura Legend and I'm trying to run my meager system (200W MTX amp pushing one 10" sub) but my amp has been cutting out/turning off. The car has a 70A alternator, and the battery is good. I didn't think anything was wrong with the alternator, seeing as I just got it replaced in May of this year after the last one died after 5+ years of use.

So, I considered getting a capacitor, but after coming to this site I found that it might not be the best thing to do, and decided to do the Big 3. Cost me about $50to $60 getting the necessary tools described in this thread, and I used 1/0 gauge wire. Hooked everything up, and still had problems with my amp cutting off.

I go to Autozone and Advance Auto and get my battery/alternator checked, and everything seems good, except for the fact that my alternator seems to be outputting only 4.8 - 10A. Holy crap, I don't see how my car is even running or charging my battery with an output like that. That is very low, correct? I'm going to go back to the place that put in the alternator, hopefully they will do something about it.

Tonight I will try taking off all my Big 3 wiring and getting an alt/battery test again, just to make sure it's not screwing something up (I don't see how this would happen, but you never know).

Anyway, just thought I would share my story. This site rocks. Lots of helpful people here.

I'm open to any suggestions, I'll update any progress I make, maybe it will help someone out there.

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[johnecon2001 5,000+ posts]

The big three isn't going to give you a false reading on what your alternator is putting out.

More than likely, you need a new alternator. Prepare yourself for sticker shock, my friend.

 

[buuzero 10+ year member]

Thanks for the response.

Well, I removed my Big 3 connections, and made sure my the wires/terminal connetions on my battery were tight, then rolled to Advance Auto to get a batt/alt test. They did the test and said the alternator was putting out ~53A and the battery ~13.5V. Earlier, when I removed the Big 3 I noticed the grounds for my neg batt-->chassis and engine block-->chassis might not have been ideal. When I sanded the paint off, I don't think I got the primer layer off! I'm an idiot, could this have been causing the low current readings from the alternator?

I then went to AutoZone to get another test, where I had a weird experience. I get the guy to test the battery, and he asks what problems I've been having. I tell him about my small system and how the amp has been cutting off. While the car is running, he looks at my battery terminals, and one of the new positive terminals I put on, and rips the wires out of my positive terminal while the car is running. //content.invisioncic.com/y282845/emoticons/eyebrow.gif.fe2c18d8720fe8c7eaed347b21ea05a5.gif WTF? You aren't supposed to do this while the car is running are you? Or does that just apply to the negative terminal? Anyway, I turn off my car, and then we tighten up the terminal/wire connection and continue with the alternator test.

I ask him if I need to rev up the car to 2000RPM, but he says no and does it from under the hood. Whatever. So, he takes the reading and says the alternator is putting out 160A peak.

Now, is that even possible? I'm going to get it tested again at the first autozone later today, because on the way home the music still cut out again after driving for about 10 minutes with the AC on and my music turned up. Seems to cut out the fastest when I'm playing things that have higher bass notes, lower bass notes don't seem to put as much strain on my system for whatever reason...

Ugh.

 

[knukonceptz 10+ year member]

If you have a 70A alternator - it will put out 70A peak, it is not under rated like amplifiers.

To address your problem, you are checking battery voltage at the battery when the problem is stemming from the amp shutting off, I would start with the amp, could be ground or power wire loose since nothing else on the car seems to have a power issue (I assume your lights dont randomly dim/cut off while driving - and I mean that in a non-audio sense) Compare voltage at both points, not just the source (battery) The source could be fine, the problem 80% of the time is in the installation

 

[buuzero 10+ year member]

I'll take your advice, maybe my grounding point isn't as good as it should be. I've had the system in for over 4 years and just started experiencing these problems in the past 10 months, and they have gotten progressively worse. Was thinking it was the alternator because I just got a new compressor back in May, and the amp seems to shut off more when I've got AC and lights going at the same time. It starts out hitting hard when I crank up and then gets a bit weaker after a few minutes of driving, and eventually starts cutting out/turning off (especially when I come to a stop... then it kicks back in a bit when I hit the gas). All the while this is happening when I have the volume at medium levels, nowhere near maxed out.

I haven't experienced any lights turning off, but my power windows roll a lot slower, especially when the amp turns off.

But yeah, I will definitely check out voltage at the amp and see what's up.

 

[Jacobman 10+ year member]

Is your gain set right? Cause i know my buddys amp was shutting off and i saw that he had the gain all the way up, lol, so i put it to 3/4 and all is well now.

 

[helotaxi 5,000+ posts]

Sounds like you have a loose connection or a corroded contact somewhere. Setscrews can work themselves loose over time and cause the kind of symtomes that you are describing.

 

[buuzero 10+ year member]

Ok, so I checked my voltages at my battery and my amp, and I get around 12.8V, which is low, correct? I have read around here that you should be getting like 14.5 to 13.5. Anyway, when the amp cuts out, I read it's voltage as around 12.4, maybe a little lower.

I got the alternator checked twice, the first place (AutoZone) that gave me the 4.8A reading before gave me about a 5.3A reading today. I took it over to the Advance Auto that showed the 53A and got it tested twice, showing ~33A and ~41A.

At this point, not really sure what's going on, but I'm going to try to see if the alt that the shop put in was under warranty and get another one.

 

[knukonceptz 10+ year member]

Voltage with Car on at 12.8V is not good. Can you check at the back of the alt (should be a large positive wire coming from the back) Just want to see if it is a cable problem. Could be a problem with the regulator or even the wiring to the regulator

 

[buuzero 10+ year member]

Connection at the back of the alt? I'll check in the morning... is this same positive connection where you do the big 3, or somehing different? Because that terminal is showing the same voltage as the battery.

Or, is it one of the terminals shown here or something completely different?

http://www.autoshop101.com/trainmodules/alternator/alt104.html

Anyway, the alt seems to be putting out ~14V when I crank and let idle, but after turning on the AC and revving the engine at 2000rpm for about 30 seconds, i test and get the low readings. 13.2V at the most, and sometimes reading at like 12.8V....

 

[knukonceptz 10+ year member]

Yes, test at the "B" terminal in that image at idle no accessories on you should be right at 14-14.4V Turning on accessories should cause a slight dip and then recover or atleast hold a solid voltage in the mid 13V range. If it continues to fall while accessories are on and voltage is the same at the back of the Alt and at battery you probably have a failing alternator.

If you can easily remove it, have it bench tested at a local shop besides Auto Zone or Advance:

http://yellowpages.superpages.com/listings.jsp?SRC=msn&CB=1&R=D&STYPE=D&C=&CID=00000494525&cbdt=Auto+Electrical+Systems+Service+%26+Repair&tidPath=00000493175%5E00000494168%5E00000494525&T=&S=&PS=15&RT=Melbourne%2C&RS=FL&RR=20&OO=1&Expand=Y&search=Find+It

 

[buuzero 10+ year member]

Removing anything in this car is a major pain in the ***. I still haven't gotten it replaced, going to try again this week. My amp is still shutting off (I am guessing because of lack of voltage) and I swear, everyone keeps telling me I might need a capacitor. I'm like, it's only a freakin 120W amp!

I'm glad I found this place, you guys know what you are doing.

Anyway, I'm pretty sure that the Autozone where I was getting the >10A readings has a broken alternator/battery tester. I took it to a different one and they said it's putting out ~35A. Now, I know their equipment isn't always accurate, but is a low current reading usually a good indicator of a failing alt?

 

[knukonceptz 10+ year member]

Stop going to auto zone, there is a thread floating around stating reasons why (think it is on termpro though)

If there test procedure is not accurate, then the results can not be used to give any relevant advice. Its like a pregnancy test with 50% accuracy

 

[SQBubble 10+ year member]

dude, your problem has nothing to do with voltage drop...well, thats wut I think

I am confident that you have a wire stripped loose somewhere that make contact the chassi when vibrations occurs, example: when high bass note hits like u said, when driving on a shitty road...

i have a battery in the back only for my 2 amplifiers..

one that puts out 800@2ohm and the other 160x2@4ohm..

the rear battery dont go over 13v much... and stays more around 12.8v, when car is on/off!! when I crank it it goes @ 11.5 and 12v sometimes , its been 3month I have it, everything is fine, its because I got only 4gauge from the front to the back, no big 3..

and that problem(amp turn off and on, constantly ...) , I did have it; when I turn up the volume, everything shake , or when I occur to shitty roads(lots over here), the amplifiers goes into protect, I thought it was my battery diying cuz of the low voltage, but no........

electrik tape on my right speaker wire in trunk fell off for some reason...and was near chassis(wire stripped), electrik taped it back like mad! Problem solved..//content.invisioncic.com/y282845/emoticons/biggrin.gif.d71a5d36fcbab170f2364c9f2e3946cb.gif

so check all ur wires that u changed, in the door, trunk, engine bay, make sure everything is secure.

hope that helped

 

[buuzero 10+ year member]

Hmm... I'll check for that wire, but my symptoms don't really come from the car "shaking".

When I first start up my car after its been sitting, and turn on the cd player, everything comes in clear and bassy like it should while I'm sitting there idling (or when I turn on the radio without cranking up the car). This is while the volume is at a medium level.

Now, if I let it sit there idling, turn on the AC, and let it sit there for about 5-10 minutes playing the music, eventually the amp starts to intermittently turn off (when the bass hits) and then eventually just stops and turns off altogether. The amp is not hot at this point either. The car will also do this without turning on the AC or lights, the Air Conditioner being on just seems to speed up the process.

Now, if I get into the car and drive some, the amp turns back on until I come to a stop. Then it fades and turns off again until I start driving again. At first I can reduce the amount of fading/cutoffs by reducing the volume and lowering the bass level on the cd player, but eventually I have the volume way down and the bass level as low as it can go and the amp still turns off. What really sucks is when I'm driving on the interstate and it happens (while going like 80mph, 3000rpm). At this point I'm guessing that the engine is using more power than the alternator is able to match? The car never cuts off, and the lights and AC still work fine, only way I really know there is a problem is through the music. Then I'm in for a long drive with no bass... ugh, it's disgusting the way it cuts out.

Yeah, I'm gonna take the advice and not go back to autozone... is advance auto any better? I'm guessing no because they use pretty much the same equipment/methods.