Brand X 320a alternator problems

[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.  

 

 

 

[JayJ]

I don't know,but sound like every manufacture blame the buyer. I actually just ordered one from them last night. It's just the 270 amp, but supposed to do 180amp at idle. We'lll see. I'm not running as much as you but I'm under the impression that this is pretty much plug and play with a smaller belt on my 2002 Chevy Silverado. But it better do what it says. Thanks for the first review I've read. Hope they got you fixed up.

[SnowDrifter]

Unfortuntaly this can be an issue on some larger alternators.

Part of why we as a forum generally recommend some pretty specific alternator brands. Mechman, DC. I believe Singer's turned a corner in the last couple years, but I have no experience with them.

Raising your idle is definitely a thing. Might be able to be done through software - trying to tighten a throttle cable or something will make you sad. Just... Don't....

For my old vehicle, I was cramming 20lbs into a 10lb bag and got a 390a alternator. The engine had a 5.5" crank pulley on it which was below turnon speed for the alt. But... I knew what I was getting into. The finals solution to that one was to get a custom 7.5" overdrive crank pulley tooled up from a company called Unorthodox Racing. Also got a couple extra ribs on there and associated power steering pulley for belt slip.

Wasn't the easiest, or cheapest solution, but IMO, was the most elegant as I had no room for dual alts or similar.  IIRC, was around $800 ish. Cost more than the alt, but it got me to where I needed to be.

Not sure how much you paid for your unit or what your other restrictions are. But, realistically, you have 3 options

1. Different alt / send to manufacturer for better idle output

2. Overdrive pulley on the crank. You really won't be able to get a smaller than 1.75" pulley for the alt. And if you somehow manage to, it'll slip. A lot.

3. Program a higher idle speed in the computer (touch base w/ your local race / dyno shop)

[LT.Smoke]

Larger Alts typically don't put much power out at idle but under load they rip it 

 

My Autotech 320 is the same way 

[sICSoundz]

Are you saying it is idling at 11.9-12.1v without playing the system? Assuming it is using a GM 4pin regulator since you keep mentioning 14.8v if so, do you have a conversion harness(Possibly stock achieves 14.8 as well I can not say I know and if not the case the following still applies as far as wiring goes if you know the orientation), What wires do you have hooked up to what? On one of the plugs you should see the letters SFLP or PLFS on GM P= Pulse and is not used.  S= Sense needs to hook up to the battery(battery is preferred over going to the stud, F=Field to switched ignition (verify key on +12vdc and key off 0vdc) ,L= Lamp needs a 50Ohm or higher resistor inline to Field and Lamp excites to charge, Sometimes the alternator will not have a F terminal and instead have a I or IG I= ignition and can be in a different order, Above still applies but L doesn't need to be used in this case as I excites. 1 wire alts self excite and the one wire goes to battery to monitor battery voltage. WARNING Connecting F and L without a resistor will cause a short and most likely blow the regulator.......  How did you test the rectifier bridge diodes? 

Sounds like it is not exciting and possibly when revved it is self exciting.  You mention reran ground to chassis, You need a ground from battery to engine (preferably on or as close to the alternator case as possible (Do yourself a favor and along with the 0 gauge +Battery to +Alternator,  ground -Battery to Body(Guessing you already did), Body to Chassis, -Battery to Alternator case, Alternator case to Chassis.This is assuming a 98  4runner is still body on frame) Your battery doesn't produce power and grounds are very important. 

[SnowDrifter]

And I just realized this thread's a year old....