H/O Alt problems Need advice/troubleshoot

[Jeffdachef 5,000+ posts]

So I got a 320 amp singer alt, put it in a few days ago and had low voltages to the point where the car would stall.

Today I put in a smaller alternator belt, upgraded the alternator ground with a dedicated ground to the battery, big 3 all done. 1/0 all around and i'm still having extremely low idle voltage, goes down to 11.8 but as soon as I rev up the rpms to 1k, I get 14.4 volts.

I bought a clamp meter and at idle i'm only getting 5-6 amps of output. at 1k rpm i'm not getting much more only 6-7. Not sure wth is going on here, didnt have this problem installing a singer h/o on my corolla back then.

I also had the alt tested at autozone before put it in and they said its a good alternator.

What are you guy's thoughts and opinions on it?

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[mylows10 5,000+ posts]

Call me Jeff 650- 483-4312 Jim I'm try to help

 

[Jeffdachef 5,000+ posts]

thanks Jim! I'll give mike a call tomorrow!

 

[blazian87 10+ year member]

Sux to hear that man.. Let us know when u get feedback. Curious to see what the problem is.

 

[negolien]

internal voltage regulator?

 

[los33]

Have you fully made sure your belt is not slipping?

 

[Jeffdachef 5,000+ posts]

Have you fully made sure your belt is not slipping?

Yeah, pretty sure it wasnt slipping even before i lowered the belt size, because ive heard alternator slipping before, its a pretty distinct noise.

I lowered the size by a whole inch and it was extremely tight.

 

[mylows10 5,000+ posts]

I think it's the sense lead wire

 

[akillj 10+ year member]

Just to clear up one part of your post, and to attempt not to spread misinformation.. Only seeing low draw without doing anything but idle, is perfectly fine. If you put a clamp on your alt, and don't see "320 amps" that's fine. You would only see that if you had your amps blasting a tone in the background. (And if your engine was at optimal RPM for your alt)

Also your low idle voltage issue, I have heard of this same issue, I believe the culprit was the alt pulley being too big? This may not be your problem, but have that checked out as well.

 

[Jeffdachef 5,000+ posts]

Just to clear up one part of your post, and to attempt not to spread misinformation.. Only seeing low draw without doing anything but idle, is perfectly fine. If you put a clamp on your alt, and don't see "320 amps" that's fine. You would only see that if you had your amps blasting a tone in the background. (And if your engine was at optimal RPM for your alt)
Also your low idle voltage issue, I have heard of this same issue, I believe the culprit was the alt pulley being too big? This may not be your problem, but have that checked out as well.

with my uncles car he's at least getting 40-60 amps of current going from the alt to the battery whereas mines is only 1/8 of that and even when i put an object on the gas pedal to keep it at 1.2k rpm its still not getting any higher then 7 amps even with my ac and stereo going on.

The new singer pulley is definitely smaller then my stock.

 

[akillj 10+ year member]

Your idle voltage drop is definitely a problem.

But this amperage thing.. i'm actually unsure what your car should be drawing just by idling. (i don't have a fluke to check mine unfortunately lol)

I do know that it should be low, just by idling. As nothing's taxing the alt, except replenishing the battery from starting, and keeping the car running. Have you tried putting a load on the alt? Give your alt some gas (like 3k rpm or some sh*t) and run a constant tone on your amp (If you have one installed at the moment). Does your voltage drop like there's not even an alt running? Or is it stable? If it's stable as if all is well, i'd guess that either your vehicle idles really low, or your alt pulley is too big.

 

[Jeffdachef 5,000+ posts]

Your idle voltage drop is definitely a problem.
But this amperage thing.. i'm actually unsure what your car should be drawing just by idling. (i don't have a fluke to check mine unfortunately lol)

I do know that it should be low, just by idling. As nothing's taxing the alt, except replenishing the battery from starting, and keeping the car running. Have you tried putting a load on the alt? Give your alt some gas (like 3k rpm or some sh*t) and run a constant tone on your amp (If you have one installed at the moment). Does your voltage drop like there's not even an alt running? Or is it stable? If it's stable as if all is well, i'd guess that either your vehicle idles really low, or your alt pulley is too big.

My Idle is at 600. At 1200 rpm, i get 14 volts at, 2-3k rpm, same thing. I stated before that i ran the car with AC on along with my system on too, only thing that change is the amperage from my rear battery going into my amp but very minimal current is flowing from the alt to the battery. Voltage drops at idle but when reved up, it doesnt drop at all even on a soft clip on my 2 brx 2400s going hard, still stays at 14.4ish at 1-2k rpm. As soon as I idle though, it stops at 12.5-12.6 for a little bit then drops straight to the high 11s.

However I haven't been playing my system or using any A/C for these past days and my battery levels have been getting pretty low, gonna have to take them out and trickle charge it tomorrow.

 

[akillj 10+ year member]

So everything's perfectly normal at high rpm? 600 rpm idle seems low imo, might be why the alt isn't sending enough voltage.. I'd guess your pulley is simply too big on the alt, not letting it spin fast enough at idle.

 

[Jeffdachef 5,000+ posts]

600 rpm was the same rpm with my stock alt which had a much bigger pulley then this new alt which has a smaller overdrive pulley. Even if its the problem happens at a complete idle, my battery should not be close to this low of a capacity after a few days drive since i gently rev on neutral at stops to keep my rpms up.

 

[boxpunch]

600 rpm was the same rpm with my stock alt which had a much bigger pulley then this new alt which has a smaller overdrive pulley. Even if its the problem happens at a complete idle, my battery should not be close to this low of a capacity after a few days drive since i gently rev on neutral at stops to keep my rpms up.

Ok a few facts for you.

The overdrive pulley is smaller than stock yes, but the stock alt was designed with that pulley. The singer alt you bought still could have too big of a pulley on it (due to your 600rpm idle)

If you haven't put a charger on your batteries before installation or after, yes your batteries could be discharged to the point where they no longer rest at 2.1v per cell.

When you clamp an alternator (you must do so with a DC clamp, not AC) you'll only get the output from the alt that meets the vehicle's needs. Quite often the vehicle never needs the full output and people say that their alt isn't putting out rated amperage.