battery/alternator weirdness - JeepForum.com
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post #1 of 21 Old 10-01-2019, 08:28 PM Thread Starter
wpatters1229
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battery/alternator weirdness

This is a 1995 yj with a 2.5l engine

I thought I had an alternator problem but then it turned out to be a bad/cracked fuse. Replaced the fuse and all OK. Now a week later I noticed the engine light on and the alternator was not charging, again.
I checked the battery voltage and it was 12.20. I checked voltage at all the fuses and on the output of the alternator and it all showed the same as the battery with no increase when the engine RPMs increased.
On a hunch, I hooked up my battery charger to the battery with everything still connected and trickle charged for 2 hrs. The measured voltage was now at 12.87. I started the engine and it showed the alternator was charging and the output to the battery was 14.40 volts.
What I am wondering, is a PCM problem with the voltage regulator or by connecting the battery charger it affected something in the alternator or because the battery was higher voltage the voltage regulator decided to kick in.
Any ideas on what to test or try next? Bad connectors on the PCM, battery bad or bad alternator.
I am guessing something with the PCM. UGH! $$$$

Thanks


Last edited by wpatters1229; 10-01-2019 at 08:48 PM. Reason: forgot something
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post #2 of 21 Old 10-03-2019, 09:25 AM
laybackman
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IF I was going to take a wild guess at what your problem is I would venture to guess that your large battery/alternator/starter cables have a lot of corrosion on the wiring under the insulation. Sometimes you can remove the cables and then twist them each back and forth vigorously several times. Place them back where they were. Now see if that made any changes the values. If it does, it is time for new cables. They are items that get completely overlooked when we search for battery/starting/charging issues. Bad battery cables cause shortened battery and alternator life also.

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post #3 of 21 Old 10-03-2019, 11:37 AM
jtec
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"I noticed the engine light on "

AND the code was?
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post #4 of 21 Old 10-03-2019, 08:15 PM Thread Starter
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code 41
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post #5 of 21 Old 10-04-2019, 06:35 AM
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Originally Posted by wpatters1229 View Post
code 41
41 An open or shorted condition in the generator field control circuit. That open or short can be ANYWHERE in the circuit to include any wire or piece of equipment.

Check all your fuses also.

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post #6 of 21 Old 10-04-2019, 09:24 AM
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I would start basic and clean you battery connections. Check and clean any and all connections that involve you alternator. Check and clean your grounds to include the ones on the engine to the body. All pretty easy. After that keep your multimeter handy and monitor what your alternator output is regularly. My guess is that it a bad connection on the battery since you possibly move a cable just enough to make a good connection with your charger. Or your battery is beginning to have a dead cell and charging it might have cleaned up that dead cell enough to work good again for a short time. If you have a battery load tester give your battery a good load test or take the battery to your nearest auto parts store, most of them can test you battery too.
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post #7 of 21 Old 10-04-2019, 10:49 PM Thread Starter
wpatters1229
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Yes, I took the alternator out and down to a parts store and they said it was good. Put it back in and made sure all good clean connections. Also cleaned the battery terminals. I also took off the ground from the engine to the firewall and cleaned all parts and added another star washer on the inside. The only thing I have not tried is checking the connections on the PCM as someone suggested.
I am leaning towards a possible battery problem because sometimes it turned over slowly even before this latest problem. The fact that the alternator turns on through the voltage regulator after doing a battery charge for a couple of hours makes me think the battery might just have a bad cell. I have a hydrometer and will check the cells.
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post #8 of 21 Old 10-07-2019, 10:31 AM
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Quote:
Originally Posted by wpatters1229 View Post
Yes, I took the alternator out and down to a parts store and they said it was good. Put it back in and made sure all good clean connections. Also cleaned the battery terminals. I also took off the ground from the engine to the firewall and cleaned all parts and added another star washer on the inside. The only thing I have not tried is checking the connections on the PCM as someone suggested.
I am leaning towards a possible battery problem because sometimes it turned over slowly even before this latest problem. The fact that the alternator turns on through the voltage regulator after doing a battery charge for a couple of hours makes me think the battery might just have a bad cell. I have a hydrometer and will check the cells.
I had an Alt go bad and throw that code. It charged correctly and test normal. Once my engine got warm though it would start bucking. Turns out the actual field coil would short to the case when it got hot.

Moral of the story weird stuff can happen.

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. It started with a $200 axle, and a few thousand dollars later I was done :)
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diagnose the real issue before you start going all Obama on it - spending mad cash you'll need for other important things.

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this is also my second set of RC springs this year. I'd rather spend the money again and get something that will last.
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post #9 of 21 Old 10-08-2019, 09:27 PM Thread Starter
wpatters1229
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Thanks for the ideas. I was going to replace the alternator but it is $123. What is strange is that the battery does not seem to be losing a charge. The alternator gauge does not seem to show any charging but the engine just turns over quickly and starts...even if you have the headlights on. I still am getting a check engine light (code 41). It is due for a smog check and wondering if that will stop me from passing even though it has nothing to do with the smog. Live in CA where they just want to get rid of old cars...mine are all 20 plus years and still have life. Why get rid of something that works and has no car payments. Starting to look at electric cars since gas is over $4 a gal out here. Pay for gas or pay for an electric..ya and then have our crappy PG&E shut off the power. Time to sign up for that trip to Mars!!
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post #10 of 21 Old 10-09-2019, 06:54 AM
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Quote:
Originally Posted by wpatters1229 View Post
Thanks for the ideas. I was going to replace the alternator but it is $123. What is strange is that the battery does not seem to be losing a charge. The alternator gauge does not seem to show any charging but the engine just turns over quickly and starts...even if you have the headlights on. I still am getting a check engine light (code 41). It is due for a smog check and wondering if that will stop me from passing even though it has nothing to do with the smog. Live in CA where they just want to get rid of old cars...mine are all 20 plus years and still have life. Why get rid of something that works and has no car payments. Starting to look at electric cars since gas is over $4 a gal out here. Pay for gas or pay for an electric..ya and then have our crappy PG&E shut off the power. Time to sign up for that trip to Mars!!
How long does it have to run before code 41 trips. Again mine did that when the field coil shorted internally. It still charged my battery perfectly. Especially when cold. You can check the field coil wires for continuity and shorts with a meter. Do you have any drivablity issues other than a check engine light?

1995 YJ. 2 inch BDS Spring lift. 1 inch shackle lift. 1.25 inch JKS Body Lift 33x12.5x15's. Engo 10,000 pound winch.

Quote:
Originally Posted by Magnum View Post
I gave the Jeep the required offering of $$, sweat, and blood, and everything works fine now. -- Jim
Quote:
Originally Posted by ldso View Post
. It started with a $200 axle, and a few thousand dollars later I was done :)
Quote:
Originally Posted by Luuca View Post
diagnose the real issue before you start going all Obama on it - spending mad cash you'll need for other important things.

Ask me how I know...
Quote:
Originally Posted by Overhead View Post
this is also my second set of RC springs this year. I'd rather spend the money again and get something that will last.
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post #11 of 21 Old 10-09-2019, 07:19 AM Thread Starter
wpatters1229
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No driveability issues. Runs fine. Radio works fine...etc. Just weird that it seems like the alternator only turns on to 14v after charging the battery with a trickle charger and both neg and plus still connected so that would mean the alternator and the PCM are in the circuit.
What test can I perform with a meter to see if the field coil is shorted? The code comes on as soon as you start the engine. It used to be intermittent but now more constant.
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post #12 of 21 Old 10-09-2019, 07:39 AM
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Check that fuse again!

Do you know what was good about the good old days? I wasn't good, And I wasn't old!

Senators and Congressman should wear uniforms like NASCAR drivers so we could identify their corporate sponsors....
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post #13 of 21 Old 10-09-2019, 11:18 AM Thread Starter
wpatters1229
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I like salutations!! Anyhow, I did check the fuses.... the first thing I did when this started happening. All new fuses. I just need to know how to check the field windings to see if they are grounded. I would assume just checking resistance between ground and each of the two connections on the alternator. But the reality that I keep avoiding is replacing the alternator and finding out it is still happening. They do not let you return alternators after installed.
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post #14 of 21 Old 10-09-2019, 02:29 PM
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Post 15 of seventeen is interesting...

https://www.jeepforum.com/forum/f12/...-41-a-1542388/

Do you know what was good about the good old days? I wasn't good, And I wasn't old!

Senators and Congressman should wear uniforms like NASCAR drivers so we could identify their corporate sponsors....
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post #15 of 21 Old 10-09-2019, 08:19 PM Thread Starter
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Just looked at that one. I might have the same problem but mine only seems to charge correctly when cold. I just noticed that it was charging this morning when it was cold and then after 5 miles I shut it off and started again and it did show charging..ugh After it warms up it stops charging and shows a code 41 which tells me a field coil is bogus. Anyone else agrees? Can these alternators be taken apart and checked for shorts on the coils? Too much work?
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