altenator issues

[cLAY]

I've lost track of what alt is from what and what you have in now but,  are you sure you are running an alt with the correct size pulley? I don't know if XJ and ZJs(V8s) use the same size pulleys. BUT I do know 100% for sure that the 150amp alt that came on the 1998 ZJ with the 5.9L used a smaller pulley than all the other V8 ZJs.

Is this a new problem or has it always been like this? I never trust the dash gauge. On my old XJ is usually sat just above the red mark, even with a 160amp alt in there. (I do remember you saying the lights seem dim though...)

[Pookapotamus]

@clay the alt i have in there now is from a zj (not sure what year or amperage) and it was the one from fraser's wrecked zj. the pulley i have on is from an xj as it has 6 groves instead of 7 to fit the xj belt. it is smaller than the zj pulley but only by about 1/8" so thats not really doing much.

this is a new problem, and yes the lights will dim and the heater fan slow untill i rev the engine up again. i am also starting to not trust the dash gauge after doing more testing last night and plan on wiring it straight to the battery or installing another gauge. my dash gauge usually sits right at 14v but now with a load on it sits at just above the red (approx 10v)

@ tinkerer i did all your tests last night. here are my results:

test#        no load voltage           loaded voltage
1                          14.3 0                            12.22
2                          14.34                             12.26
3                          .02                                    .08
4                          .01                                    .04

no load voltage was with just the engine running no other lights or accesories on (750 rmp)
loaded voltage was with everything that i could turn on including headlights, driving lights and 4 55w offroad lights. (750 rpm)

so what this is telling me is that the alt cannot supply the voltage needed at idle.

[Pookapotamus]

ok found out that the zj alt that is 136 amp has a larger diameter case therefore this alt i have is only a 90 amp. still need to find one of these then.

[Tinkerer]

@ tinkerer i did all your tests last night. here are my results:

test#        no load voltage           loaded voltage
1                          14.3 0                            12.22
2                          14.34                             12.26
3                          .02                                    .08
4                          .01                                    .04

no load voltage was with just the engine running no other lights or accesories on (750 rmp)
loaded voltage was with everything that i could turn on including headlights, driving lights and 4 55w offroad lights. (750 rpm)

so what this is telling me is that the alt cannot supply the voltage needed at idle.

Edit: ok found out that the zj alt that is 136 amp has a larger diameter case therefore this alt i have is only a 90 amp. still need to find one of these then.

Like you said in the last bit of the quote above, it seems to be the alternator, as those voltage drops on the positive and ground wiring are well within normal.  It just can't supply the current required to keep the voltage high.

I'll be honest, at 750 RPM, mine doesn't keep up either, but that's when it is almost "ok". At about 1000 RPM, it is pretty much normal, but I'm sure mine is more than a 90 amp alt (though I haven't tried to verify) as it's factory in the '04 TJ with AC and almost all the bells and whistles *and* I don't have all the added off-road lights etc.

[Pookapotamus]

i was just talking to my guy at napa, looking for a new 160 amp alt. he told me that my computer is regulating my voltage and not the little thing with 4 wires on the back of my alt, does anyone know what that thing is??

so i am figuring that the regulator in my comp is the issue here and am going to try to look into how to fix the comp so that it tells the alt to put out more volts. either that or bun the jeep to the ground and buy a toyota! 

[esi]

The 4 wire thing on the back of the alt is to adjust output, but not all alt have them. It's usually a 3/4" square plug that you can pull out then turn and plug back in. Heavier alts usually have them but I haven't seen too many in lighter duty apps.

[Pookapotamus]

ok so i am considering picking up an external voltage reg and installing that, just bypassing the internal voltage reg in the pcm.

[FiEND]

voltage regulator doesn't really do much. 

the main circuit board converts the AC from the alternator to DC 14.5 volts... or so.

the regulator reads the vehicle voltage from the battery and then either turns on charging (say at 12.5 volts or turns off charging at 14.5 volts)

so, if the regulator is not working, you will not see any voltage increase from the alternator as it will not start charging.  there is only ON and OFF.

voltage regulator doesn't really do much. 

the main circuit board converts the AC from the alternator to DC 14.5 volts... or so.

the regulator reads the vehicle voltage from the battery and then either turns on charging (say at 12.5 volts or turns off charging at 14.5 volts)

so, if the regulator is not working, you will not see any voltage increase from the alternator as it will not start charging.  there is only ON and OFF.

voltage regulator doesn't really do much. 

the main circuit board converts the AC from the alternator to DC 14.5 volts... or so.

the regulator reads the vehicle voltage from the battery and then either turns on charging (say at 12.5 volts or turns off charging at 14.5 volts)

so, if the regulator is not working, you will not see any voltage increase from the alternator as it will not start charging.  there is only ON and OFF.

voltage regulator doesn't really do much. 

the main circuit board converts the AC from the alternator to DC 14.5 volts... or so.

the regulator reads the vehicle voltage from the battery and then either turns on charging (say at 12.5 volts or turns off charging at 14.5 volts)

so, if the regulator is not working, you will not see any voltage increase from the alternator as it will not start charging.  there is only ON and OFF.

voltage regulator doesn't really do much. 

the main circuit board converts the AC from the alternator to DC 14.5 volts... or so.

the regulator reads the vehicle voltage from the battery and then either turns on charging (say at 12.5 volts or turns off charging at 14.5 volts)

so, if the regulator is not working, you will not see any voltage increase from the alternator as it will not start charging.  there is only ON and OFF.

voltage regulator doesn't really do much. 

the main circuit board converts the AC from the alternator to DC 14.5 volts... or so.

the regulator reads the vehicle voltage from the battery and then either turns on charging (say at 12.5 volts or turns off charging at 14.5 volts)

so, if the regulator is not working, you will not see any voltage increase from the alternator as it will not start charging.  there is only ON and OFF.

voltage regulator doesn't really do much. 

the main circuit board converts the AC from the alternator to DC 14.5 volts... or so.

the regulator reads the vehicle voltage from the battery and then either turns on charging (say at 12.5 volts or turns off charging at 14.5 volts)

so, if the regulator is not working, you will not see any voltage increase from the alternator as it will not start charging.  there is only ON and OFF.

voltage regulator doesn't really do much. 

the main circuit board converts the AC from the alternator to DC 14.5 volts... or so.

the regulator reads the vehicle voltage from the battery and then either turns on charging (say at 12.5 volts or turns off charging at 14.5 volts)

so, if the regulator is not working, you will not see any voltage increase from the alternator as it will not start charging.  there is only ON and OFF.

voltage regulator doesn't really do much. 

the main circuit board converts the AC from the alternator to DC 14.5 volts... or so.

the regulator reads the vehicle voltage from the battery and then either turns on charging (say at 12.5 volts or turns off charging at 14.5 volts)

so, if the regulator is not working, you will not see any voltage increase from the alternator as it will not start charging.  there is only ON and OFF.

voltage regulator doesn't really do much. 

the main circuit board converts the AC from the alternator to DC 14.5 volts... or so.

the regulator reads the vehicle voltage from the battery and then either turns on charging (say at 12.5 volts or turns off charging at 14.5 volts)

so, if the regulator is not working, you will not see any voltage increase from the alternator as it will not start charging.  there is only ON and OFF.

voltage regulator doesn't really do much. 

the main circuit board converts the AC from the alternator to DC 14.5 volts... or so.

the regulator reads the vehicle voltage from the battery and then either turns on charging (say at 12.5 volts or turns off charging at 14.5 volts)

so, if the regulator is not working, you will not see any voltage increase from the alternator as it will not start charging.  there is only ON and OFF.

voltage regulator doesn't really do much. 

the main circuit board converts the AC from the alternator to DC 14.5 volts... or so.

the regulator reads the vehicle voltage from the battery and then either turns on charging (say at 12.5 volts or turns off charging at 14.5 volts)

so, if the regulator is not working, you will not see any voltage increase from the alternator as it will not start charging.  there is only ON and OFF.

[Pookapotamus]

so what your really trying to say is???

[FiEND]

not that many things to go wrong in that area.

alternator
wiring
regulator
shorted battery (watch temp).

isn't the voltage regulator an external one, in the ECU, on the 1995?  should throw a code?

you eliminated three causes a long arse time ago, just don't or can't accept it.  i've been getting txt messages and emails and phone calls asking why you don't take the alt in for testing as it is obviously faulty.  heck, today i got a letter from brasil and what did it say?

"obter o maldito alternador testados"  "get the damn alternator tested"

[FiEND]

here's what you need to know...

http://www.bc4x4.com/tech/2004/jeepalt/

i got one from a dakota durango at pick n pull a month ago, works great.  there are plenty of 90amp there which would work very well in your jeep also.  worked fine in mine for many many years.  just went bigger cause i could for the same money and may help out winching a bit.

[Pookapotamus]

"take the alt in for testing as it is obviously faulty"

wrong! i have had all 3 of my altenators tested thay are all fine!

battery tests fine. all wiring is 4 gauge.

still having this issue, but i am begining to think i am chasing a white whale. the only thing i have left to do is swap a larger amp alt into and see if that helps. although this really dosent make much sence as i have not always had this issue and with just heater and headlights on my lights dim, but seems to be the only fix.

[morerpmfred]

There is a remote chance that it is not grounded . Where the ground goes to the motor below the alternator there is a plate that it is attached to ( going by memory ) and that plate is bolted to the block , a part of the motor mount ?. the bolts are like about a sixtenth of an inch to long , bottomed out and yet it is a bad ground and the solution is to grind of a little bit of the bolts and or move the ground wire . there was a technical service bulletin back in the day

[BlackYJ]

Here is a really dumb question but worth asking.  Is your serpentine belt tight enough?  If it is not, the belt will slip and therefore not allow the alternator to work properly. 

I run a 90 amp alternator with my 8274 winch, which is one of the highest drawing winches, lights, heater, stereo all that crap and don't have a problem in my YJ.

[Pookapotamus]

yup its tight!