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Charging issue with Check engine light

SanDiegoOverland

NAXJA Forum User
Location
San Diego
1992 Cherokee 4.0l
Aw4 auto
Np231
d30/d35 w/abs and A/C




Couple days ago, the check engine light came on and stayed on upon start up. I noticed it, but was on my way to work, and couldn't pull the code right then.

I stopped for gas, filled up, and to my surprise the light was gone. I didn't dismiss it, knowing very well that this was a "soft" error or code, meaning that something was brewing, and would invariably get worse if I ignored it.

I pulled the codes on my OBDI system and got error code 41.

This translates to:

"Alternator Field Switch: Switch not operating correctly and check charging system"


It's a very strange problem to have because upon startup you get the check engine light on and the voltmeter reading low, and then all of a sudden, the volts go right up to 14 and stay there like there's nothing wrong. It will do this at a stand still while I warm the engine a bit or after a few minutes of driving.

This morning I noticed that the headlight output was actually directly impacted by the low voltage output, as they became noticably brighter when the volt meter jumped up to 14v. (It's the first time it made me think that its something other than an incorrect sensor reading, as up till now it had no effect upon start up, or while driving.)

Researching this morning,I found this previous thread:
http://www.naxja.org/forum/showthread.php?t=1015341&highlight=wierd+charging+issue

Which seems very similar if not the same as my situation.:shhh:

I'm going to follow the diagnotic advice of Joe_Peters in that thread to see if I can isolate the source.


Anyone else dealt with this? What was the fix?:huh:

All arrows seem to point @ the battery, alternator or battery terminals/wiring have too much resistance.
 
Cleaned off both terminals and while the battery was out checked the wiring for any visible cuts, frays or looseness. Didn't find anything overt, so i'll have to dig in a bit more and see what i find.

I did put a multimeter on the battery and got a reading of 12.6v.

I'll keep y'all updated...feel free to post up.
 
I'd suspect bad brushes or slip rings on the alternator. Next time it does this, try taking a piece of pipe or something and tapping the alternator with it as it runs. If it recovers, it's time to check the brushes.
 
I'd suspect bad brushes or slip rings on the alternator. Next time it does this, try taking a piece of pipe or something and tapping the alternator with it as it runs. If it recovers, it's time to check the brushes.


if so, can I pull the brushes and hit both the brushes and the slip rings with an eraser or emery cloth? Or is there some other way to keep from having to replace the whole unit?

(Never pulled apart a Jeep alternator)
 
Had same symptoms and code 2 weeks ago, replaced alt. due to diode failure. However, that failure may have been brought on by the crappy ground cable I found shortly afterwards. Sometimes you have to cut back a little of the cable insulation to inspect for dark, almost black cable. This is not an indication of failure, but a sign of increasing resistance and heat. Also feel the cable for soft spots or sections that may be begining to breakdown. The cable should feel tight inside of the insulation, not loose or frayed at all. Do the same for the big red one too, and don't skimp on cleaning the cable ends and terminals.
 
if so, can I pull the brushes and hit both the brushes and the slip rings with an eraser or emery cloth? Or is there some other way to keep from having to replace the whole unit?

(Never pulled apart a Jeep alternator)
The Nippondenso alternator has a removable brush holder, so you don't have to disassemble the alternator. You can pull the brush holder and clean the slip rings, but don't use anything more than an eraser or crocus cloth. The brushes don't need dressing, and if anything they're probably too short already. If the brushes are worn, you must either replace the brush and holder assembly or solder new brushes into the holder (not hard to do). But if you find the slip rings gouged up, as often happens, you're probably better off replacing the alternator. You can put new brushes on a scored slip ring and they'll work, but they won't last very long. If the slip rings are just dirty and scorched you can clean them off, but be careful (no sanding, not even fine), because they must be very very smooth.
 
ive had this code pop up for a few reasons,
first time: alternator completely dead
second time it would come and go as the alternator was int he process of dying
third time bad battery caused the light


have the battery and charge system load tested. a good battery/alternator/starter shop can do this test for you and tell you what part is bad. alt or battery

but it is one of the two.
 
Had same symptoms and code 2 weeks ago, replaced alt. due to diode failure. However, that failure may have been brought on by the crappy ground cable I found shortly afterwards. Sometimes you have to cut back a little of the cable insulation to inspect for dark, almost black cable. This is not an indication of failure, but a sign of increasing resistance and heat. Also feel the cable for soft spots or sections that may be begining to breakdown. The cable should feel tight inside of the insulation, not loose or frayed at all. Do the same for the big red one too, and don't skimp on cleaning the cable ends and terminals.


OK, will do. This is such a wierd problem!

Again, I got in it today, and it read around 10amps on the voltmeter in the dash (not very accurate, I know) when I fired it up, and it turned on the engine light. As I came to the stop sign at the end of the street, it jumped up to 14amps like normal, brightening the headlights. It stayed that way for the rest of the 25mile drive to work.

I parked in the lot, turned it off, and then back on again just to see...still @ 14amps, with no check engine light.

It's not like it has a ton of time to "warm up" or anything. The end of my street is about 20secs away from my driveway. Not enough to change much as far as temperature goes. In fact, my rig doesn't warm up completely until I'm 3-4 streets away, nearing the freeway.



EDIT: Y'all were posting the above comments as I was writing this, so I'll go back and read what you wrote. THANKS guys! :)
 
The Nippondenso alternator has a removable brush holder, so you don't have to disassemble the alternator. You can pull the brush holder and clean the slip rings, but don't use anything more than an eraser or crocus cloth. The brushes don't need dressing, and if anything they're probably too short already. If the brushes are worn, you must either replace the brush and holder assembly or solder new brushes into the holder (not hard to do). But if you find the slip rings gouged up, as often happens, you're probably better off replacing the alternator. You can put new brushes on a scored slip ring and they'll work, but they won't last very long. If the slip rings are just dirty and scorched you can clean them off, but be careful (no sanding, not even fine), because they must be very very smooth.

10-4
 
ive had this code pop up for a few reasons,
first time: alternator completely dead
second time it would come and go as the alternator was int he process of dying
third time bad battery caused the light


have the battery and charge system load tested. a good battery/alternator/starter shop can do this test for you and tell you what part is bad. alt or battery

but it is one of the two.


Ok, sounds good. I think I'll do this next.

Also, I did a good job cleaning the terminals and checking the wires, but I'll probably do a resistance test as well as a "pull the insulation down" visual test tonight just to make sure bad wiring isn't what caused the problem in one of those components.

Honestly the alternator looks like the original unit, and the battery was in the rig when I got it last year, so both are unknown quantities as far as remaining lifespan, so a good checkup is a smart thing, even if they both test as being fine. (which I don't expect, after hearing similar experiences)
 
I'd suspect bad brushes or slip rings on the alternator. Next time it does this, try taking a piece of pipe or something and tapping the alternator with it as it runs. If it recovers, it's time to check the brushes.


Ok, did this test. it absotutely responded by recovering when I tapped it.

I had my multimeter on the battery terminals when I first started it and got a reading of about 12v-12.2v.

I gently tapped the top of the alternator with my breaker bar, and immediately the engine note changed, and the voltage jumped up to about 13.8-14.0
 
replace alternator with OEM
problem solved


Yeah, that's what I'm thinkin' I'll do. Called the dealer and they have a rebuilt factory unit for 120.00.

That seems like a pretty competative price, actually.

I'm gonna call around today and see if I can get a recommendation from a few trusted mechanics, for a alt. shop to see how much a rebuild of my unit would be, just for comparision

I also have the pleasure of having John and BorderParts right around the corner in La Mesa. He's got great pricing. Definitely worth a shot.

In the back of my mind, I know I have the ability to pull the alternator and replace the brushes myself, so that's something, if I can find the parts, that I'd consider, too. (It'd sure be a lot easier on my finances:))
 
Yeah, that's what I'm thinkin' I'll do. Called the dealer and they have a rebuilt factory unit for 120.00.

That seems like a pretty competative price, actually.

I'm gonna call around today and see if I can get a recommendation from a few trusted mechanics, for a alt. shop to see how much a rebuild of my unit would be, just for comparision

I also have the pleasure of having John and BorderParts right around the corner in La Mesa. He's got great pricing. Definitely worth a shot.

In the back of my mind, I know I have the ability to pull the alternator and replace the brushes myself, so that's something, if I can find the parts, that I'd consider, too. (It'd sure be a lot easier on my finances:))

I've replaced brushes in three ND alternators over the years. The brushes are cheap, and require soldering in, not a big deal. BUT, of the three, only one had good slip rings. You can bodge in new brushes anyway while you hunt for a good replacement, but it's a holding action. They won't last nearly as long. The last one I did, I went to a local rebuilder, and he just handed me the brushes with no charge. Predictably, my starter packed up soon thereafter, and guess who I got to rebuild it?
 
I've replaced brushes in three ND alternators over the years. The brushes are cheap, and require soldering in, not a big deal. BUT, of the three, only one had good slip rings. You can bodge in new brushes anyway while you hunt for a good replacement, but it's a holding action. They won't last nearly as long. The last one I did, I went to a local rebuilder, and he just handed me the brushes with no charge. Predictably, my starter packed up soon thereafter, and guess who I got to rebuild it?


Talked to a alt shop today that was recommended to me, and he said that he'd have to see it and test it for him to know.

Brushes + labor = about $20-30.00

Brushes, slip ring + labor = about $80.00-$90.00

At that point, I feel like I might as well just go the dealer and get their reman'd factory unit for $120.00 as it'll have a warranty, and will have had its bearings replaced if it needed 'em. (in theory:laugh3:)
 
Talked to a alt shop today that was recommended to me, and he said that he'd have to see it and test it for him to know.

Brushes + labor = about $20-30.00

Brushes, slip ring + labor = about $80.00-$90.00

At that point, I feel like I might as well just go the dealer and get their reman'd factory unit for $120.00 as it'll have a warranty, and will have had its bearings replaced if it needed 'em. (in theory:laugh3:)
I don't know why you'd want to mess around...(actually I do)
but time is becoming way more valuable than money. :)
 
I dont mean to hi jack, but i need some help with issue as well.

I had the same intial issue with the check engine light. Iwould start it up the light would come on. I would shut it off and restart and the check engine light would go away. I took the battery to have it test. I was told it was good but had a low charge. I charged the battery over night and replaced the alternator and cleaned to connections. Started up, the gage showed 14v. I took a test drive and when I turned the AC on the gauge dropped to about 10v. Turn the AC off voltage back to 14. Does anyone have any suggestions? Did I install a bad altinator or do I have another problem.
 
I dont mean to hi jack, but i need some help with issue as well.

I had the same intial issue with the check engine light. Iwould start it up the light would come on. I would shut it off and restart and the check engine light would go away. I took the battery to have it test. I was told it was good but had a low charge. I charged the battery over night and replaced the alternator and cleaned to connections. Started up, the gage showed 14v. I took a test drive and when I turned the AC on the gauge dropped to about 10v. Turn the AC off voltage back to 14. Does anyone have any suggestions? Did I install a bad altinator or do I have another problem.

Tighten the belt properly. Get the KR2 gage from Napa and measure the tension instead of guessing.
 
If Lawson's first step doesn't help (though I think it will), you should also remember that the dash gauge is not an accurate reflection of actual battery voltage, so always test at the battery itself before considering a diagnosis as final. It's not as big an issue with later ones, but older XJ's, especially the Renix era ones, will show a huge voltage drop when you turn up the fan, but it's a quirk of the voltmeter circuit.
 
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