Brand X 320a Alternator Issue

[Met]

I recently purchased a Brand X 320a Denso alternator (internally regulated) for a 98 Toyota 4runner. I'm having an issue with output at idle. It drops to 11.9-12.1v at idle but reaches 14.8v like it should at about 1100 RPM. The alternator was advertised to put out 160a at idle and nothing was mentioned about having to raise my idle speed. It has a 1.7in pulley and I'm pretty sure a smaller pulley doesn't exist. The sense wire is connected to the positive battery terminal (I've also tried connecting it directly to the alternator positive stud) and I ran the ignition line into the ACC fuse using an add a fuse. The alternator came with a harness that was supposed to be plug and play, but after that didn't work I ran it myself to be sure. There is a 470 ohm 1/2 watt resistor on the ignition line which Brand X is saying it needed to not "pop" the regulator. I've replaced the belt and there is no noticeable slip (I've cranked the tension up for testing to be sure), I've tried 2 AGM batteries, 1 that I know is good and one that is brand new) I have a few Yinlong lithium banks, I just haven't installed them yet as the build is far from done). I've re-ran my power and grounds (brand new 0awg OFC, soldered terminals), all runs are less than 3ft, grounded to the chassis and I verified the connections are solid (angle grinder to bear metal). I've tested the rectifier bridge on the alternator which tested fine. My old alternator(140a) puts out 14.8v at idle with no issues.

During testing, a few random times the alternator held 14.8v like it should at idle. This usually happens after holding the RPM at ~1100 for about a minute and then letting it drop back down. It will hold 14.8v indefinitely until I restart the engine. After a restart, the idle is back to ~12v. This doesn't happen every time either, I've only been able to recreate it a few times.

It's been really difficult to get solid help from Brand X, they immediately blamed my install. After assuring them it isn't (I don't think they're convinced) I asked if I needed a smaller pulley. They said the correct way to fix it would be to raise my idle RPM. I told this is not a possibility. They are saying that I can send it back so they can lower the output which I guess will fix the issue?

Before I send it back I figured I would reach out here as I find it odd how it randomly will put out the correct voltage at idle. Is there any thing else I could test?

Any help would be appreciated.

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[Evil Monkey36]

The only input I can add is that his alts are supposed to typically be factory replacement style. Plug and play. I got a Brand X 250-270 amp alt (depends on who's rating it). It was plug and play and I had the same issue almost as you. I did my big 3 0G and I only got 1 yellow top. After a few back and fourths on email I went and got his kit for $30ish bucks to bypass my pcm. I have a GM though. I never ever dip below 14v at my worst anymore. It setpoint my Alt to run at 14.7 all times. Is this maybe something you can do?

 

[Popwarhomie 5,000+ posts]

Is it dropping voltage at idle WHILE running the stereo? Or without it running? Do you notice at a certain idle RPM that it does this or is it random?

I would either swap to an overdrive pulley or send it back. They normally don't recommend overdrive pulleys so you don't over spin the alt. But if you aren't redlining your 4 runner I don't think you will ever have that issue.

 

[Met]

The only input I can add is that his alts are supposed to typically be factory replacement style. Plug and play. I got a Brand X 250-270 amp alt (depends on who's rating it). It was plug and play and I had the same issue almost as you. I did my big 3 0G and I only got 1 yellow top. After a few back and fourths on email I went and got his kit for $30ish bucks to bypass my pcm. I have a GM though. I never ever dip below 14v at my worst anymore. It setpoint my Alt to run at 14.7 all times. Is this maybe something you can do?

This alternator is already internally regulated

Is it dropping voltage at idle WHILE running the stereo? Or without it running? Do you notice at a certain idle RPM that it does this or is it random?

I would either swap to an overdrive pulley or send it back. They normally don't recommend overdrive pulleys so you don't over spin the alt. But if you aren't redlining your 4 runner I don't think you will ever have that issue.

I'm still building the wall in the rear, so this is just idle with nothing pulling on the system. Not even headlights. The voltage is consistent, at idle its 12.1v, as I raise RPM to 1100, it rises with it to 14.8v (the setpoint) and stays at 14.8v until I let off the throttle. It drops back down to 12.1v once it reaches idle again.

But like I said, a few times I would hold 1100 RPM for a minute or so, and then when I would let off the gas and let the RPM drop back to idle and the voltage would hold 14.8v indefinitely until I restart the car. But this only happened 3 times, out of the 30 or so times I've tried to recreate it. I don't understand why a few times it worked right, but the rest of the times it does not.

I appreciate the replies!

 

[Popwarhomie 5,000+ posts]

This alternator is already internally regulated



I'm still building the wall in the rear, so this is just idle with nothing pulling on the system. Not even headlights. The voltage is consistent, at idle its 12.1v, as I raise RPM to 1100, it rises with it to 14.8v (the setpoint) and stays at 14.8v until I let off the throttle. It drops back down to 12.1v once it reaches idle again.

But like I said, a few times I would hold 1100 RPM for a minute or so, and then when I would let off the gas and let the RPM drop back to idle and the voltage would hold 14.8v indefinitely until I restart the car. But this only happened 3 times, out of the 30 or so times I've tried to recreate it. I don't understand why a few times it worked right, but the rest of the times it does not.

I appreciate the replies!

I would send it back. Sounds like the "turn on RPM" is set too high. I'm not a big fan of CES myself since he uses used parts but alot nut hug the **** out of him and his alts.

 

[Met]

I would send it back. Sounds like the "turn on RPM" is set too high. I'm not a big fan of CES myself since he uses used parts but alot nut hug the **** out of him and his alts.

Yeah, I regret not just going with mechman/singer. I had some other issues but I'm not really trying to put anyone on blast. But it's been a pain in the ass from the get go.

 

[Popwarhomie 5,000+ posts]

Yeah, I regret not just going with mechman/singer. I had some other issues but I'm not really trying to put anyone on blast. But it's been a pain in the ass from the get go.

I feel you there for sure. That's why I went DC Power. Expensive but worth it cause it is a PITA to change out if I ever had to again.