NST Pulley Set Alternator Issue

[MGargano]

I picked up and installed a full set of NST pulleys a little over a year ago. To my knowledge, they were not underdrive or overdrive pulleys, just the lightened version (http://shop.microimageonline.com/NST-Pulley-Set-NST-P3.htm), but apparently (thanks to CTScott's diagnosis) my alternator is under-charging the battery.

I'm not sure if this is a new issue or if it has been doing this for the past year- either way, I'm curious why/how the non-underdrive pulley set could be causing this.

When running, the ScanGauge puts my voltage at 14.1 maximum, without any kind of load (amplifiers, head unit, etc.). Even 14.1 is rare- it's usually around low- to mid-13's.

I did a search and saw some people having the same problem with the 10% underdrive pulley, but I'm curious if anyone has run into this with the standard lightened set and what a potential fix might be. Something as simple as tightening the belt? Or something more drastic?

[1NZYaris1]

Simple solution , put the OEM pullie back on and retest , i bet you will
finf it is the Alternator that is Fualty ,and it will have nothing to with the Pullies .:thumbsup:
It might also pay to check all connections betwen the alternator and the battery .
Aswell as the battery main fuse.

[MGargano]

Simple solution , put the OEM pullie back on and retest

Should I replace all three pulleys with OEM? Or just the crank pulley?

[1NZYaris1]

Just The Crank :thumbsup:

[shinlee]

I've got all 3 pullies on for over 2 years, never, not once, have I had a problem with my alternator, and thats with 3 subs in the car too.

Alternator is going out, no biggie, but it's not the pullies fault

[MGargano]

I've got all 3 pullies on for over 2 years, never, not once, have I had a problem with my alternator, and thats with 3 subs in the car too.

Alternator is going out, no biggie, but it's not the pullies fault

I wasn't really blaming the pulley for doing anything wrong- I'm more curious to know if I received the correct one and/or if it was installed correctly by the shop I took it to.

For instance, if I received a 10% underdrive pulley by mistake, that would explain the lower voltage I'm seeing. Would a loose belt do the same thing?

[goliath1812]

Even with the 10% underdrive pulley set, I thought there were still supposed to be no issues with under-charging...?

[MGargano]

Even with the 10% underdrive pulley set, I thought there were still supposed to be no issues with under-charging...?

That's what I thought too, but I'm hoping for some confirmation so I can rule out the pulleys as the problem. I don't want to go through the hassle of putting the OEM pulley back on if it turns out to be a bad alternator.

I'm guessing a max of 14.2v while moving at speed with no load is considered "low"?

[lilredrocket]

Just size up your stock pulley to your NST one if the one on your car is smaller than stock you have the under drive one.

[MGargano]

Just size up your stock pulley to your NST one if the one on your car is smaller than stock you have the under drive one.

Just checked- the two pulleys are identical in diameter, so I guess I have the right one installed, not the underdrive.

I guess that leaves the alternator as the culprit?

[Bluevitz-rs]

What's the voltage @ 2500-3000 rpm? and how many miles/km on it?

[MGargano]

Mileage is 10,906.

Voltage with no load at 3,000rpm is 14.1v- but it definitely does not hold that voltage while driving. It fluctuates, but usually hovers in the low- to mid-13's

[Bluevitz-rs]

That's about normal

[shinlee]

with the car on, normal output should be 13.7 to 14.5

with the car off, the battery should be about 12.5

I used to manage an Autozone, and I've done god knows how many alternator checks. If you're getting 14.1 then you should be fine. It sounds to me like there may be an issue in the wires, something not connected properly or something of that sort. A loose (incredibly loose) belt will cause it to not charge properly, but just pull on the belt while it's off, and if there's a lot of play, either tighten it up or replace it.

[MGargano]

with the car on, normal output should be 13.7 to 14.5

with the car off, the battery should be about 12.5

The battery holds at ~12.5v when off, but the "normal output" for me is lower than 13.7- usually closer to 13.2-13.4. I'm not sure if those 1/10's of a volt are a cause for concern, really.

If you're getting 14.1 then you should be fine

It doesn't hold steady at 14.1 for any extended length of time- low 13's are "normal" for me

A loose (incredibly loose) belt will cause it to not charge properly, but just pull on the belt while it's off, and if there's a lot of play, either tighten it up or replace it.

I inspected the belt when I compared the pulley sizes- it was nice and tight, no play or slack at all.

[severous01]

if you buy the underdrive set isnt the alternator smaller to compensate and it's actually over-driven?

my experience with underdrive kits any way...jsut the alternator, not pump or any others, jsut the alternator to compensate for slower belt speed

[cruz-gsr]

thats what i normally get on mine

[MGargano]

I tightened the belt very slightly last night and today everything seems to be "normal"- between 13.7 and 14.2.

[Kenshin]

Stupid question but is your ground to your batter tight? Because I had fluctuations in my voltage while driving around to where even the steering was tougher at times (of course cause it's electric). So I checked my ground and it wasn't loose loose but wasn't tight either.

Just a stupid question cause yeah. . .I've been there. . .

[MGargano]

I checked and tightened both battery cables this morning. At first it seemed to help- 14.1v at idle and at speed, regardless of load.

This continued for a while, but after a 40 minute parkway drive (where the voltage stayed at 14.1), the voltage dipped as soon as I moved from the parkway to slower-speed city streets.

It never went lower than 13.6 though, so I guess that's an improvement. No more 13.2s, though I'm still frustrated at the inconsistency.

[cali yaris]

if you buy the underdrive set isnt the alternator smaller to compensate and it's actually over-driven?

No, the NST alternator pulley is the same size as stock.

MGargano's inconsistent voltage is an interesting thing; I'm not technical enough to know, but how could a pulley cause that?

[MGargano]

I've pretty much ruled out the pulley as the issue, since it's the same size as OEM.

I'm still curious what's causing the inconsistency, though.

Battery, cables, and pulley are out as causes, from what I can tell.

[Aothachos]

yea i just tightened my belt couple minutes ago, my water pump pulley was getting a slight groove from the belt on it and it was squeaking, so i just took a breaker bar and my landlord helped me (he works on cars) so everything works fine now. I have a full NST lightweight pulley set with the 10% underdrive and never had a problem so far and I drove about 40,000 miles with them on now a little over a year, and i've been through hot weather to the deadly winter storms we just had in ny here and no problems :)

[cali yaris]

MGargano, have you checked that inconsistent voltage in more than one location? seems like that might help locate the root cause.

[MGargano]

MGargano, have you checked that inconsistent voltage in more than one location? seems like that might help locate the root cause.

I haven't- I've just been going by what the Scan Gauge is displaying. Where else can I check?

[Bluevitz-rs]

Right at the battery with a volt meter.

[MGargano]

I was doing that at first until I remembered the Scan Gauge had a voltage gauge. I can only check at the battery when I'm sitting in the driveway at idle, which is not where I'm having the problem- it fluctuates most when I'm at speed.

[MUSKOKA800]

Alternator (expensive) or voltage regulator (less expensive/cheap). Not sure in the case of Yaris but sometimes the voltage regulator is integrated into the alternator. The battery could also be nearing its end.
If you problem resurfaces you might have a shop do a load test to pinpoint the culprit.

[MGargano]

I actually bought a new battery and the issue remained, so I ruled that out as the cause and returned the new battery.

The Yaris' voltage regulator is integrated into the alternator, so I don't know how cheap it'd be to replace.

I was hoping to figure this out on my own, but it looks like my only option is a local auto electric repair place since I've checked out everything I can think of.

[Bluevitz-rs]

Mileage is 10,906.

With only 11K miles on it, why don't you just bring it to the dealer and ask them if there's a problem with what it's doing or it it's normal.

[MGargano]

With only 11K miles on it, why don't you just bring it to the dealer and ask them if there's a problem with what it's doing or it it's normal.

I have two amplifiers and HIDs connected to the battery along with NST pulleys, so I can't imagine that they'd cover anything alternator/electrically-related under warranty.

[Bluevitz-rs]

So do I, and I've never had any questions asked about it. As long as they aren't MASSIVE 1000+ Watt amps each.

If you have the tunes pumping as you drive with the fan going, the lights on, it's totally normal for the voltage to fluctuate. That why you normally need a big capacitor hooked in parallel with the amp wiring. It reduces voltage fluctuation.

[MGargano]

So do I, and I've never had any questions asked about it. As long as they aren't MASSIVE 1000+ Watt amps each.

I just have a feeling they'll blame the amps and HIDs, whether they're what's really causing the problem or not. Maybe I can disconnect them and hide the wires, so they can't take the easy way out and use them as the cause.

If you have the tunes pumping as you drive with the fan going, the lights on, it's totally normal for the voltage to fluctuate.

I'm seeing the fluctuations with and without the load, which is what's bugging me. If it was only happening with everything turned on, I wouldn't be concerned at all.

That why you normally need a big capacitor hooked in parallel with the amp wiring. It reduces voltage fluctuation.

I would definitely look into this if the fluctuation was only happening with the amps on. It's frustrating that it's happening all the time.

[Yariz]

I picked up and installed a full set of NST pulleys a little over a year ago. To my knowledge, they were not underdrive or overdrive pulleys, just the lightened version (http://shop.microimageonline.com/NST-Pulley-Set-NST-P3.htm), but apparently (thanks to CTScott's diagnosis) my alternator is under-charging the battery.

I'm not sure if this is a new issue or if it has been doing this for the past year- either way, I'm curious why/how the non-underdrive pulley set could be causing this.

When running, the ScanGauge puts my voltage at 14.1 maximum, without any kind of load (amplifiers, head unit, etc.). Even 14.1 is rare- it's usually around low- to mid-13's.

I did a search and saw some people having the same problem with the 10% underdrive pulley, but I'm curious if anyone has run into this with the standard lightened set and what a potential fix might be. Something as simple as tightening the belt? Or something more drastic?




Says on their site you may have to change the belt. Did you get this fixed?

[rob323]

If the Scangauge is still showing over 13 volts, how can the alternator be "under-charging" the battery?

[MGargano]

I ordered an alternator with 22,000 miles for $60 from the same junkyard I got the "S" gauge cluster (yard4.com), so hopefully I'll have my answer in a few days.

[CTScott]

If the Scangauge is still showing over 13 volts, how can the alternator be "under-charging" the battery?

For a lead acid battery, the optimal charging voltage is 2.26 and 2.36V/cell (which = 13.56 to 14.16 Volts).

[MGargano]

For a lead acid battery, the optimal charging voltage is 2.26 and 2.36V/cell (which = 13.56 to 14.16 Volts).

I'm confused again, since I'm getting 13.5-14.2v, according to the Scan Gauge. Is this too low? Or is it the fluctuation regardless of load that's the problem?

[CTScott]

I'm confused again, since I'm getting 13.5-14.2v, according to the Scan Gauge. Is this too low? Or is it the fluctuation regardless of load that's the problem?

As long as it isn't sagging below that then you are probably OK, but the alternator and regulator should be able to maintain a steady 14.1 at idle.

[MGargano]

As long as it isn't sagging below that then you are probably OK, but the alternator and regulator should be able to maintain a steady 14.1 at idle.

It's definitely not maintaining any kind of steady voltage, at idle or while moving and regardless of the absence or presence of a load.

I guess I'll just swap the alternator and see what things look like with the "new" one.

[MGargano]

I swapped the whole thing today with an '09 alternator with around 1,000 miles on it ($70). No change in voltage; it continues to fluctuate regardless of load and at idle.

When moving at a decent speed, it generally holds at 14.1v, but at idle and slower speeds, it fluctuates from 13.5-14.1.

[MGargano]

Well after no change in voltage with the new alternator, I decided to do the "Big 3" upgrade.

I ran 1/0 wire from the alternator to battery +, and chassis/engine to battery -

Zero improvement. Everything is exactly the same- voltage still drops to, and fluctuates around, 13.5 at idle/slow speeds and holds steady at 14.1 as long as I'm moving at a decent speed, all regardless of load.

Hooray for wasting time and money.