Calgary Jeep Association
4x4 Related Groups => Tech Talk => Topic started by: Pookapotamus on December 11, 2010, 05:44:13 PM
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having some problems with my 95 xj, last couple of weeks when i stop at a light or just idle and have my lights on or heater on high my voltage drops below 10v. so i figured the old 90 amp alt was on its way out. last night my voltage was even lower so i got an 136 amp alt out of a zj (thanks fraser) and swapped that in today. no change its still doing the same thing! johnny thought it might be the battery so we swapped in his, still no change. then figured it was the voltage regulator and i had a couple sitting around and swapped that out, still no change! i still sit at just above 9v on idle if i have my lights on.
the 4.ol is not idling too low or anything like that but what am i missing?? what else could be causing this? and yes i guess it is possible that the zj alt is bad too but it worked fine in frasers when it was taken out. (although i think it might have been in the jeep that fraser wrecked, dont know if that would kill the alt.
so whats my next step?
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Check the ground connections, specifically the cable that runs from the engine to the firewall and the wire that runs from the battery to the fender well.
Vince
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Check the ground connections, specifically the cable that runs from the engine to the firewall and the wire that runs from the battery to the fender well.
Vince
I was going to suggest the same thing - ground issue.
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i was thinking that too just did not want to re wire! ::)
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Buy a TJ we don't cook the altenator on every puddle. ;)
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Are you checking the voltage with a mulitmeter or the dash gauge? Whats the voltage at the battery and the post on the alt? Could have a bad cable.
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i have only checked it with the dash gauge, i know something is wrong as all my lights dim pretty badly. i am going to pick up some wire and connectors in the am and get to work see if i cant fix this. thanks for the advice all!
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Pick up a multimeter while you are at it. Otherwise its hard to say where the problem is and you're just throwing parts at it.
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well i ended up replacing every wire related to the charging circuit, redid all the grounds, supplies and alt wiring. they were not visably bad but did not test well with the ohm meter. runs better now still noticing some drop in voltage with everything i can turn on, around a 1v drop at idle.
thanks for all the advice.
Pook
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Buy a TJ we don't cook the altenator on every puddle. ;)
and SHA-ZAAM!
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Buy a TJ we don't cook the altenator on every puddle. ;)
Pook wouldn't know what to do if his vehicle's "frame" stopped flexing. After all, that represents 25% of his suspension travel. ;D
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you guys are so funny! >:(
so this worked fine in the garage but driving the wife to school this morning it was doing the same thing! now what?
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I have a multi meter in the jeep right now actually, I can stop by on my way home if you'd like to borrow it.
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i have one, but thanks. stop by anyway i have a socket for you.
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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?
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its bolted to the back of the alt, already swapped it out with another that i had, and still no change.
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the new alternator yes. the old alternator though, was external? controlled by the ecu or pcm ?
mine i am running internal regulator and external since i did the swap to the higher amp.
the internal regulator will regulate the voltage but not sure it will turn the alternator on and off to charge (the internal relay). that is controlled via the 2 little wires that connect to the alternator, that is the relay connection that starts the alternator charging.
so if the ECU / PCM whichever is borken, might not work even with an internal regulator.
only a voltmeter will tell you if it is charging though
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yes it is charging, start jeep and have no accesories on and it is charging at 14v. turn on heater to full and it starts dropping, turn on lights (just headlights) and it drops further down to 12v. keep turning things on and it slowly gets to the red line. with everything on, (heater, defrost, headlights, driving lights, 4 55w spot lights, radio & amps and other misc) it holds just above red line. if i rev the engine with everything on it only comes back halfway. with just headlights and heater and defrost and i rev the engine it comes back a good 75 - 90%.
am i just being picky? i just really hate stopping at a light and all my lights dim.
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I guess your new alternator is toast as well. you can really only test with load put to it as you are.
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What are you getting with everything on EXCEPT the heater motor? I've seen heater motors start to draw too much power when the start to fail. Although it usually shows up as a blown fuse, resistor pack or fuse.
With everything on how many volts are you seeing at the battery vs the alt post?
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AHA!! Dana... you were having heater problems before....
cLAY is a smart cookie!!
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not quite....
it's a 140 amp alternator. if the heater is drawing enough current to severely drain the alternator (and the big fat juicy wire connecting it to the battery) then the [much smaller] wiring on the heater motor would melt and catch fire.
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Alternator output is based on load and engine speed, at idle the pulley is turning it's slowest, so output is at it's lowest. Winter months are hard on alts cause every electrical device is on and it spends too much time at red lights idling. Bump the gearbox into neutral and pick up the idle slightly to help it out. Turn off your rear defrost and wipers till your moving again.
But 140 Amp is pretty big, try a smaller alt pulley and your dash voltmeter is at the tail end of a big load of electrics, probaly reading low. Hook up a volt meter to your alt output terminal and see what's there, if the volt on your battery is more than 0.5 volts lower, add another main wire from alt to battery
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heater motor and fan resistor are 1 month old.
all my testing has been done with a multimeter at the batery.
wires from the alt and every other wire in that area are copper core 4 gauge wire.
@ clay i have tried many different combinations of electronics that are on, the heater motor does seem to be one of the biggest draws but like i said i just replaced it. the biggest draw seems to be the defroster on the rear windo, but i rarely use it. i am having this problem even with just headlights and driving lights on.
@ mike s i have considered a smaller pully but this seems to be a work around i would rather fix the issue instead of mask it.
a few things i am considering:
1 the alt out of the zj i got from fraser is the one that was in his jeep that got crashed. (possibly affecting the alt and it is bad)
2 the alt out of the zj is it really a 140amp alt?
3 redoing wires from the fuse block to some of the major drawing electrics.
4 i am just being picky, (jeeps are supposed to have their lights dim at lights its a sefety feature)
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Since
- you are measuring at the battery with a multimeter
- even revved up, it only comes up to half-way (what is that anyways? I presume it's half-way to 14 volts from the red line, but a voltage would be great.)
It sounds like either
- the alternator can't put out enough current
- the regulator is not providing enough field current to fully drive the alternator to capacity
Two questions / comments come to mind:
- How much voltage is at the alternator versus the battery when revved up with all accessories on? I know you put bigger cables, so it shouldn't be there, however, this is the "acid test".
- Is there a temperature sensor on the battery for that year vehicle? It may be saying the battery is "hot" and chooses to limit the field current, and therefore the charging current. (This is typically only on ECU controlled charging.)
Is the battery good? Is it fully charged? I've seen them draw a bunch of current due to being bad, so in combination with the accessories, the alternator couldn't keep up!
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batery is an optima yellow top not compleetly sure if it is good and i have not yet completly ruled it out as being bad. i have boosted with another battey to see if i get the same dropps and i do. so i am thinking it is good. i want to test more tonight and actually write down what i am getting instead of just going from memory.
the 95 xj does not have a batt temp sensor. it has an external regulator on the alt.
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Since the bearing in the one I gave you might have been on its way out, could you try swapping the regulator from it onto yours?
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batery is an optima yellow top not compleetly sure if it is good and i have not yet completly ruled it out as being bad. i have boosted with another battey to see if i get the same dropps and i do. so i am thinking it is good. i want to test more tonight and actually write down what i am getting instead of just going from memory.
the 95 xj does not have a batt temp sensor. it has an external regulator on the alt.
Sounds good... sounds like it isn't the battery if that boost battery was left in parallel during some testing.
As I understand it, the regulator/alternator can put out 14V under light load (you already said so), just not under large load, even at higher rpms.
For diagnosing what can seem like an alternator issue, the 4 measurements that can be done easily with a multimeter are:
- Battery Voltage (Red to Battery+, Black to Battery-) In ideal conditions, 14V unless the battery is hot..
- Alternator Voltage (Red to Alternator output, Black to Alternator body) In ideal conditions, 14V, may be higher if measures voltage at the battery.
- Positive Voltage Drop (Red to Alternator output, Black to Battery+) In ideal conditions, 0V, but typically a very small value < 1V. Gets higher with larger load.
- Ground Voltage Drop (Red to Battery-, Black to Alternator body - could be backwards, but you'll just get a -ve voltage) In ideal conditions, 0V, but typically a very small value < 1V. Gets higher with larger load.
http://wikicars.org/en/Alternator (http://wikicars.org/en/Alternator)
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@ fraser i already swapped out the voltage regulator, twice i had three of them.
@ tinkerer i will try all your tests tonight and record the voltage.
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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.
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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...)
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@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.
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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.
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@ 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.
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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! >:(
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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.
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ok so i am considering picking up an external voltage reg and installing that, just bypassing the internal voltage reg in the pcm.
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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.
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so what your really trying to say is???
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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"
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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.
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"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.
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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
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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.
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yup its tight!
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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.
That's cuz you use lots of belt dressing. A good shot of belt drssing will have your alternator putting out at least 200 amps.
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yup its tight!
Thats what SHE said :o. Maybe you need more belt dressing ;D
Sorry I could not resist