Alternator output

kccrd · **Joined:** Thu Mar 08, 2007 10:35 pm **Posts:** 267

What should the output of our nipendenso alternator be?

Joe Romas · **Posted:** Tue Aug 19, 2008 8:58 pm

Are you acking about current or voltage? I saw the current listed in the FSM. Voltage is controlled by the BCM.

Pablo · **Joined:** Thu Feb 02, 2006 10:06 pm **Posts:** 1201

The stock alternator is anemic. I think it is rated at 85 AMPs in the CRD. On my list is a new (rebuilt) one around 130-160. Have not decided on the exact amount yet.

DarbyWalters · **Posted:** Wed Aug 20, 2008 7:45 am

All I am sure of is that it can't be that good. My headlights dim when I put down the windows.

scrambledKJ · **Posted:** Wed Aug 20, 2008 7:55 am

My AC almost stops blowing when I roll the windows up.

My libby build sheet says 136 amp alt.

My CJ is 63 amp. The CJ doesn't lie...

Travis

DarbyWalters · **Posted:** Wed Aug 20, 2008 2:20 pm

I seem to remember that the stock KJ was 135 or so...and one model (maybe Renegade) has a 160 or so.

gmctd · **Posted:** Wed Aug 20, 2008 2:50 pm

You guys need to check the connections at both battery posts, and have the battery load-tested - grounding and connections are causative for those symptoms - that and a weakening battery - you could put the alternator from the TITANIC on the KJ, and BCM would demand only the programmed amount of current - the alternator is not stand-alone, and has no autonomy - DCJ has been doing that scheme since back in the early '90's, with ECM monitoring system voltage and controlling charging current - 136 amps is 136 amps on any alternator capable of 136 amps, same on a 136million amp alternator - ECM is only gonna demand spec'ed programmed output, confirmed by the sense line - at one time, was even a battery temperature sense line, where ECM would reduce charging current if battery was too hot - check your battery, charging system, and wiring

Uffe · **Posted:** Thu Aug 21, 2008 5:01 am

gmctd wrote:

You guys need to check the connections at both battery posts, and have the battery load-tested - grounding and connections are causative for those symptoms - that and a weakening battery - you could put the alternator from the TITANIC on the KJ, and BCM would demand only the programmed amount of current - the alternator is not stand-alone, and has no autonomy - DCJ has been doing that scheme since back in the early '90's, with ECM monitoring system voltage and controlling charging current - 136 amps is 136 amps on any alternator capable of 136 amps, same on a 136million amp alternator - ECM is only gonna demand spec'ed programmed output, confirmed by the sense line - at one time, was even a battery temperature sense line, where ECM would reduce charging current if battery was too hot - check your battery, charging system, and wiring

Nice post by a knowledgeable guy

DarbyWalters · **Posted:** Thu Aug 21, 2008 6:54 am

The problem with the dimming of the lights ect. happens only when you are at idle and the engine is not spinning the alternator with any gusto. Start up the beast...radio on...turn on the headlights...hit the window switch and DIM...

gmctd · **Posted:** Thu Aug 21, 2008 8:45 am

Alternator rated output is not spec'ed at crankshaft rpm, it is at alternator shaft rpm - the 136a alternator pulley is roughly 1/4 diameter of the crankshaft drive pulley - @ 750 crank rpm the alt is turning 3000rpm - it will put out 136a\14.2v at 750 crank rpm if necessary to keep up with drain - as drain increases causing increased loading on the engine, ECM increases fuelrate to sustain increasing load - you won't see an rpm increase on the tach, but you would notice a power output increase if you could monitor that parameter - it's a voltage\connectivity problem if the lights dim when additional normal load is applied - I'm not talking a winch, or 1000kw off-road lighting, or a 12v field'n'stream air compressor, or a 1kw boom-box power amplifier at full load - normal accessory loading - the lights didn't dim from the factory because of pristine electrical connections and a full-capacity-rated battery - weather and age and trips to the salty beach and muddy off-roading have oxidized every connection in the wiring harness, particularly those at the battery posts, starter connection, all engine\body grounds, the fuse spades in the power block, the relay spades in the power block, the relay contacts, the headlight socket connectors and other lighting connectors - if the headlights are dimming, it's electrical resistance due to normal oxidation, worn exciter brushes with reduced spring tension or\and weak diode(s) in the alternator, even slipping belt on the driven pulley, reduced battery capacity, etc - when BCM senses voltage drop, response is much quicker than human sensory capability, so you shouldn't see any change - you'll know it's bad when the headlights begin to blink dim along with the turn signals

onthehunt · **Posted:** Thu Aug 21, 2008 3:00 pm

Mine has dimmed since new. It's had two ecm changes also. It's just the way it is.

JL Rockies · **Posted:** Thu Aug 21, 2008 3:12 pm

Back in my early burglary years, we used to put smaller pulleys on the alt to make it spin faster at idol. This way you could terrorize the intersection with your boomin system without worry of power loss.

kccrd · **Joined:** Thu Mar 08, 2007 10:35 pm **Posts:** 267

I took the alternator to a repair shop and the guy grabbed it by the pulley and said here's your problem the one-way clutch on the end of the pulley is broken he then took it off the alternator pushed out the insides and there it was a big broken spring. He said let me see if I have a pulley that will match and after comparing a few pulleys he found an exact pulley that would work he put it on with the correct nut and said see you later no charge. I later found out the replacement pulley from the dealer is around $71.00 what an over engineered pulley when a regular old time pulley works fine probably better since it will be charging the battery all the time now. The hardest part is putting the serpentine belt back on.

gmctd · **Posted:** Fri Aug 22, 2008 9:43 pm

The one-way pulley is necessary to prevent belt breakage and alternator rotor coil damage and tensioner damage- the 4cyl Diesel puts some terrible dynamics into the serp belt system, which is why the engineers spec'ed this pulley specifically for this engine - no other DCJ engine uses this pulley on an alternator - and FYI - when you're running down the fwy at 3500rpm, the alternator shaft is spinning at 4x crankshaft rpm, so you get 14,000rpm - I prefer replacement oem equipment on this system

kccrd · **Joined:** Thu Mar 08, 2007 10:35 pm **Posts:** 267

If my new pulley is the exact same size it will not spin any faster than the one way pulley and I was told the only reason for the clutched type pulley was to free spin when there is no load on the alternator, thus saving some fuel and load on the engine. That explanation did make a little sense but not worth the $70.00 cost since my pulley is doing the same thing but without all the internal parts to go bad in the future and another failure. The alternator is putting out 14.2 volts with all my lights on plus the AC on and the lights on my light bar turned on at idle seemed good to me. What do you think?

gmctd · **Posted:** Sat Aug 23, 2008 12:27 am

That's a one-way clutch - only way the alt shaft could free-wheel is if the alternator shaft was spinning faster than it's driven pulley - that would indicate the alternator could also run as a motor, 'n est ci pa? I've never seen an alternator motor over when power is applied - your repair guy is a dufus, even if he did get you temporarily rolling again - the reason for that pulley is as I explained, no other - keep us informed as to 'progress'

kccrd · **Joined:** Thu Mar 08, 2007 10:35 pm **Posts:** 267

The only thing I have noticed is it seems to start up quicker run smoother at idle the internal fan seems to run quieter and there is no noise coming from that stupid pulley. I also noticed that the 3.7L gas motor has a standard pulley on it.

gmctd · **Posted:** Sat Aug 23, 2008 5:32 pm

The operative word in the 3.7 designation does not appear to be DIESEL, right?

kccrd · **Joined:** Thu Mar 08, 2007 10:35 pm **Posts:** 267

That is true. But what is the only function of a alternator?

gmctd · **Posted:** Sat Aug 23, 2008 6:49 pm

To survive the unusual torsional characteristics encountered when attached to a comparativey large displ 4cyl Diesel engine, with only two violent combustive thrusts on the crank per revolution (180*), where a 6 is smoother with three (120*) and an 8 is much smoother with four (90*)?

Alternator output

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