it reads discharge for a bit then after driving goes up to where it should be(14 vlts)in the morning it cranks slow and the chk eng lite comes on sometimes.the batt is very old so i replaced it over the weekend because it failed all of the tests at autozone.everything seemed fine that day with a fully charged batt but yesterday it started acting up again doing the same thing.95 chreokke w 4.0.
-
Welcome to the new NAXJA Forum! If your password does not work, please use "Forgot your password?" link on the log-in page. Please feel free to reach out to [email protected] if we can provide any assistance.
is my alt bad?
- Thread starter markg
- Start date
When you get a voltmeter on it, it should put out at least 13.5 vdc - which the guage indicates it's doing. Checking the diodes would be next, but if one is bad, the voltage would be lower.
"Reads discharge" I assume to mean the voltage drops? As for "acting up," so far all that implies is the "reads discharge." Slow cranking could be from an old starter as much as the battery.
Codes just mean the computer isn't getting voltage readings within the range it's programmed to accept. The mechanical condition is what you have to still determine, and the cause. Out of range volt readings can be caused by corrosion at the terminals, bad ground connections, etc.
Your best option is to get the alternator tested while running - which the parts houses can do. At that point you will know more than what the codes are pinging for.
"Reads discharge" I assume to mean the voltage drops? As for "acting up," so far all that implies is the "reads discharge." Slow cranking could be from an old starter as much as the battery.
Codes just mean the computer isn't getting voltage readings within the range it's programmed to accept. The mechanical condition is what you have to still determine, and the cause. Out of range volt readings can be caused by corrosion at the terminals, bad ground connections, etc.
Your best option is to get the alternator tested while running - which the parts houses can do. At that point you will know more than what the codes are pinging for.
winterbeater
NAXJA Forum User
- Location
- Royal Oak, Michigan
Usualy alternators work or they don't. First you need to disassemble your battery cables and other grounds and clean them with scotchbrite or sandpaper. Clean the debris off with electrical contact cleaner, brake cleaner, spray start, etc., and reconnect. When the motor is not running, you should have 12 - 12.5 volts. When it is running, it should go up to 13.5 or so. Also clean the connections on the alternator. Because you say that your voltage goes up as you run it, the alternator is probably still good.
thank you
i didnt know they could test it on the vehicle.i tested it before the batt change w a voltmeter and it was reading discharge.the batt has since been changed and im still having the same problem.ill look at the connections 1st.many of my friends have the stock one still in and they are much older than the one in my 95.
i didnt know they could test it on the vehicle.i tested it before the batt change w a voltmeter and it was reading discharge.the batt has since been changed and im still having the same problem.ill look at the connections 1st.many of my friends have the stock one still in and they are much older than the one in my 95.
5-90
NAXJA Forum User
- Location
- Hammerspace
1) The IP voltmeter is a notorious liar. Verify any suspect readings with a "known good" multimeter.
2) DO NOT do the old "pull the battery cable while the engine is running" test on any vehicle with electronic controls. You stand about an even chance of frying something important!
3) The "on-vehicle" test using the little red Bear ARBST tester that most chain stores have now is reasonably accurate. I wouldn't trust their benches tho - if you've already got the thing off, take it to an alternator/starter shop and have them test it for you. They'll usually throw it on the bench for free, and their bench will not only tell you Pass/Fail, but will usually tell you why it failed!
4) Sounds like you've got OBD-I. I've got a listing of Jeep OBD-I codes on my site - 12 is "Battery Disconnect" (set when you changed your battery,) and 41 is "Alternator Field Not Switching Properly" - meaning the ECU doesn't see the alternator responding to the regulator output signal. (http://www.geocities.com/JeepI6Power/obd1.html - all codes listed per FSM.) So, the alternator going stupid on you is a definite possibility, and should be the next thing you test.
A good habit to get into is to, anytime you fix anything that could throw a code on you (you'll see the list if you click the link,) disconnect the battery cables and touch them together for ten seconds with the engine OFF. This should clear just about all codes, save 12. You may want to invest in a Chrysler OBD-I code reader (they can be had for a reasonable fee - usually less than $100) so you can check things like this yourself, if you don't already have one. You'll note that there are two colours used on the DTC charts I've got up - the ones with the RED background will light up the CEL/MIL, while the ones with the GREEN background will not. So, having a scanner so you can just check for codes every few months isn't a bad idea - something could be happening that the ECU isn't telling you about...
2) DO NOT do the old "pull the battery cable while the engine is running" test on any vehicle with electronic controls. You stand about an even chance of frying something important!
3) The "on-vehicle" test using the little red Bear ARBST tester that most chain stores have now is reasonably accurate. I wouldn't trust their benches tho - if you've already got the thing off, take it to an alternator/starter shop and have them test it for you. They'll usually throw it on the bench for free, and their bench will not only tell you Pass/Fail, but will usually tell you why it failed!
4) Sounds like you've got OBD-I. I've got a listing of Jeep OBD-I codes on my site - 12 is "Battery Disconnect" (set when you changed your battery,) and 41 is "Alternator Field Not Switching Properly" - meaning the ECU doesn't see the alternator responding to the regulator output signal. (http://www.geocities.com/JeepI6Power/obd1.html - all codes listed per FSM.) So, the alternator going stupid on you is a definite possibility, and should be the next thing you test.
A good habit to get into is to, anytime you fix anything that could throw a code on you (you'll see the list if you click the link,) disconnect the battery cables and touch them together for ten seconds with the engine OFF. This should clear just about all codes, save 12. You may want to invest in a Chrysler OBD-I code reader (they can be had for a reasonable fee - usually less than $100) so you can check things like this yourself, if you don't already have one. You'll note that there are two colours used on the DTC charts I've got up - the ones with the RED background will light up the CEL/MIL, while the ones with the GREEN background will not. So, having a scanner so you can just check for codes every few months isn't a bad idea - something could be happening that the ECU isn't telling you about...
1) I wish the mod to "improve" the veracity of the meter was generally published - but I know cutting the printed circuit board isn't for everyone.
2) Keep beating this drum, I do at the parts counter. Too many young guys have been taught '60's stuff by completely out of date old men! (I'm 56, so there.)
A) Don't pull the batt cable B) Charge a battery on a charger FIRST to full voltage diagnosing problems - low voltage batteries will not make an electronic regulator kick in late model alternators, and they are rated at PEAK output IMHO, not continous - the industry gets lots of new ones back that burnt out recharging dead batteries. C) Codes don't mean it's broke, replace it. They mean it's out of the acceptable range of electric volt readings. You have to find out why. (Just click the gas cap tighter next time.)
3) I use the computerized hand held tester at work, it's generally pretty accurate. I've had good feedback from customers. The new computerized bench tester is reliable, too - at least with alternators you get an on screen pass/fail for the circuits, diodes, and output. I'd like the starter side to load it, but adding a universal "flywheel" won't happen. Mileage, symptoms, and erratic responses are still part of the process.
4) OBD readers are available for less than $50 at Harbor Freight - but all you get is the code number, not the explanation, like the $200 we loan out to the parking lot. Having your own is nice, but parts houses do have them, too, with the full and confusing language officially adopted. The owner has to operate it, we can't, it's against federal law as too many codes were erased under warranty. If the owner is discovered doing that, it could impair any claim - y'all be careful.
I'm just chiming in with the working side of it - it never hurts for some to see it again, we all need some refresher, and some never knew . . .
2) Keep beating this drum, I do at the parts counter. Too many young guys have been taught '60's stuff by completely out of date old men! (I'm 56, so there.)
A) Don't pull the batt cable B) Charge a battery on a charger FIRST to full voltage diagnosing problems - low voltage batteries will not make an electronic regulator kick in late model alternators, and they are rated at PEAK output IMHO, not continous - the industry gets lots of new ones back that burnt out recharging dead batteries. C) Codes don't mean it's broke, replace it. They mean it's out of the acceptable range of electric volt readings. You have to find out why. (Just click the gas cap tighter next time.)
3) I use the computerized hand held tester at work, it's generally pretty accurate. I've had good feedback from customers. The new computerized bench tester is reliable, too - at least with alternators you get an on screen pass/fail for the circuits, diodes, and output. I'd like the starter side to load it, but adding a universal "flywheel" won't happen. Mileage, symptoms, and erratic responses are still part of the process.
4) OBD readers are available for less than $50 at Harbor Freight - but all you get is the code number, not the explanation, like the $200 we loan out to the parking lot. Having your own is nice, but parts houses do have them, too, with the full and confusing language officially adopted. The owner has to operate it, we can't, it's against federal law as too many codes were erased under warranty. If the owner is discovered doing that, it could impair any claim - y'all be careful.
I'm just chiming in with the working side of it - it never hurts for some to see it again, we all need some refresher, and some never knew . . .
5-90
NAXJA Forum User
- Location
- Hammerspace
I haven't seen that one (at least, not lately.) Is it taking the voltage signal from somewhere a little more reliable?
"Completely out of date" is a good way to put that - the problem is not that their skill isn't up to scratch, but that they haven't changed with the times.
(B) and (C) are entirely correct. OBD (and, to a greater extent, OBD-II) will help you figure out where to start looking, but you still don't need to throw parts at the problem to make it go away!
Is that the Snap-On, MAC, or MATCO tester? My alt/starter guy uses the Snap-On one, and I keep wanting to get one for myself. All I have is a 100A load box (which fits neatly with most of what I do anyhow.) I'm happy to hear they've updated the benches - back when I was holding down the counter, it checked for output voltage at about .2A. Hell, I've got a couple of hand flashlights that draw more than that!
I picked up a pretty good reader at Sears for $60 a while ago. And, if you need a reference for codes, I've got Jeep codes pulled from FSMs up on my site - so you can go there. As I said above tho, all a code can really tell you is that there is something wrong, and where to start checking...
Yeah, I feel the same way. I know even I need a refresher from time to time, and I've been doing this since I was six (started with 1950's and 1960's cars 'way back when...)
stewie
NAXJA Forum User
if in fact your alt is bad then its a good time to upgrade. why go for a stock replacement when an upgrade is the same cost or just a little more? when my stock alt siezed a bearing i went for a ZJ 136 amp alt in my 95 XJ. it was an easy mod and just about as easy as straight replacing it. there are a few write ups on here about it. and 5-90 makes a kick @ss set of battery cables. its on my wish list but has been put on hold following a lay off. soon though.
Similar threads
