A couple months ago I replaced my failed OEM alternator (just over 200k and kept it to rebuild) with a new aftermarket CS144 made by DB Electrical. I was planning to do the Big-7 cable upgrade via the kit from JeepCables.com but didn't have it yet when my alternator crapped out.

Anyhow, everything seemed great, but a few days ago I started noticing lower voltage ranging from 11.6v to 12.3v when idling around 650-700rpm at stops. Also noticed the dash and headlights dimming/fluctuating as well as a slight whining noise when giving a bit of throttle. Voltage gets back to the 13.8v - 14.8v range and noise seems to go away when rpms get above 1200. Just wondering if the new alt is failing prematurely or if I have issues elsewhere. I plan to put the new cables in this weekend to take that out of the equation.

Do you know the size of the cs144's pulley is? More then likely it's to big (causing the alternator to spin to slow). Stock 4runner v6 pulley size is 55mm. IIRC the cs144 shaft is 17mm and the denso is also 17mm. So might want to swap out the pulleys if they fit.

Had this same issue. High Idle it would charge at 13.8ish and drop to 10v when warm at 600-700 rpms, then went to a 48 or 46mm pulley. Charges at 14.8v. Shortly after that I put in a 14.8v set point voltage regulator.

I got my cs144 from the junkyard, and rebuilt it with a 200a upgrade kit.

Pulley on the DB alt is 62mm:
Alternator 4.6 Concours 94-97, DeVille 96 , Eldorado Seville 93-97 | DBE

Found this 53mm (stock?)
http://www.metroautoinc.com/new/inde...=1349,951,1026

I'm wondering if the voltage regulator just might be on the fritz, because it was originally showing 13.8+ at low idle. I contacted DB about the issue and they sent me a replacement because I was still in the warranty window.

The one on the bench - I bet it only needs brushes. And might as well inspect the brushes on your replacement while you have it out.

New brushes after only a few months?

On the replacement? Well, I've heard of remans not having the brushes replaced.

The DB Electrical alts are advertised as new aftermarket items to the OEM specs. Seems pretty legit and they get good reviews from the research that I did before making the purchase. They come with documentation from the bench test results. See attached.

Regulator activation shows 405 rpm, Secondary regulation shows 14.9, and Alternator turn on shows 1182 rpm. Now I'm wondering if the alt is good, but I'm just not getting enough rpms at low idle for it to kick in. Almost thinking (like recommended earlier in the thread) that the pulley OD is a bit too big. Just need to figure out what OD is gonna make 1200 rpm at my low engine idle rpm which is around 600 rpm. Does that sound about right?

Attached Images

 

We had a member on the forum here put a smaller pulley on an oem alternator. So it would give him 14.0v at idle as he was tired of his rig fan slowing down and lights dimming at idle especially in the winter. So fixed the issue by changing the pulley. I may do the same as I don't like that with my heating fan running full with the lights and both wipers slowing down at idle...:-) I really don't need any more power in my rigs but I like faster fan speed in the winter..

So a smaller pulley on either oem or larger alternator will effectively correct the give you higher voltage /amps at idle.

So your thought of a smaller pulley will fix this problem. :-)

Maybe this will help for calculations.
Pulley Calculator

You don't want to go to small. It will over rev the alternator toasting it almost immediately.

Does anyone know the crankshaft pulley OD (Toyota 13408-62040) for the alternator belt offhand...and/or the stock ratio to the stock alternator pulley OD?

I found this, but nothing about the cs-pulley OD yet:

A 3rd generation Toyota 4Runner typically has an alternator pulley ratio of around 2.5:1 to 3:1; meaning the diameter of the crankshaft pulley is roughly 2.5 to 3 times larger than the diameter of the alternator pulley.
Explanation:
Calculating the ratio:
To find the exact ratio for your vehicle, measure the diameter of both pulleys and divide the crankshaft pulley diameter by the alternator pulley diameter.
Importance of the ratio:
This ratio determines how fast the alternator spins relative to the engine RPM. A higher ratio means the alternator spins faster at a given engine speed, which can be beneficial for high power accessory needs.

I just stumbled across this thread on tacomaworld: Cs144 Alternator Questions | Page 3 | Tacoma World

These are all calculated for the 5VZ

I measured the circumference with some wire and came to 19.625" and a diameter of 6.247" when I was having the same issue.

So my calculations came to this:

55mm (2.165") cs144 pulley
6.247 ÷ 2.165 = 2.88
2.88 × 600 = 1728 rpm's @ idle

48mm (1.88") cs144 pulley (what I have now)
6.247 ÷ 1.88 = 3.32
3.32 x 600 = 1992 rpm's @ idle

55mm @ 5500 rpm's v6 redline= 15840

48mm @ 5500 rpm's v6 redline = 18260

You can do more math to finely dial in the rpm's, but 55mm is what I'm switching to as the 48mm spins the alternator to fast for my liking.

Love it...great feedback! I was initially thinking 55mm without having done any calcs or knowing the exact stock dims. 53mm seems to give a 3:1 ratio...which jives with what I found earlier. I'm thinking the 55mm should do the trick at less rpms though.

I found this helpful to double check my maths:
Alternator Pulley Ratio Calculator - Calculator Academy

After more calculations, I've just ordered a 52mm or 2.05" pulley. It's a happy medium between 48 and 55mm. Got it from ebay. The seller has lots of other cs144 pulleys too. As close as I could get for a 3:1 ratio.

Pulleys

3.04 × 600 = 1824 rpm's idle
3.04 × 5500 = 16720 rpm's redline

Can't go wrong for $15. Think I'll give it a go as well. I was just trying to get the max OD that would get me to around the 14v I was seeing at 1200rpm with my alt. Thanks again for chiming in on this thread!