NST Pulley Set Alternator Issue

[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]

Originally Posted by cali yaris

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]

Originally Posted by MGargano

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]

Originally Posted by Bluevitz-rs

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]

Originally Posted by 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.

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.

Originally Posted by Bluevitz-rs

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.

Originally Posted by Bluevitz-rs

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]

Originally Posted by 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, 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.