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Unread 09-23-2014, 08:55 PM   #1
JohnC7
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1997 ZJ 
 
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Replacing Alternator, Bosch?

I have a slow drain on my battery , its not old and well its a good one. A northstar battery to be specific. I believe its the alternator since the charging is at 13.7-13.8 volts even when driving, so its not properly charging the battery. I called up my local auto parts store and they priced out a new bosch alternator 120 amp for 191. Is bosch any good?

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Unread 09-24-2014, 11:31 AM   #2
sebian
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13.7 - 13.8 is perfectly fine. If you have a slow drain, aka parasitic draw, then there is a circuit that is open in your vehicle some where. You will have to determine what and where. I usually look towards aftermarket stereos or amps, but other circuits like the tailgate could be the culprit as well.

I don't have any testing procedures off hand, but I am sure that someone with more intimate knowledge of the ZJ electrical system will hop into the thread.
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Unread 09-24-2014, 11:42 AM   #3
zjosh93
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Sebian is right, voltage should generally be between 13.5 and 14.5 so you are good there. Did you check the voltage at the battery while running or are you going off the gauge? My gauge reads low.

Plenty of threads about parasitic drains if you search for them.
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Unread 09-24-2014, 11:47 AM   #4
JohnC7
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I do have a multimeter to test. I guess I'll check for amp draw. I know the voltage from a cigarette lighter outlet. I'm pretty sure it's the alternator. A charge that was once 14.4 is now 13.8. I almost doubt it's the amps for the sound system I have in there since this never happened with my old battery.
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Unread 09-24-2014, 12:39 PM   #5
Pierre_r
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Your alt is fine.
Mine goes from the marker after 14 to the one that is before 14 after some driving

It is normal for the alt to charge less after a while.
Thats because it has charged the battery and the power it makes then is only used to keep the engine/radio/lights running.
With a new battery there are more power from the start so it dosent need to charge it as long as it had to do with your old.

And yes Bosch is good, Stay the **** away from Hella.
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Unread 09-25-2014, 09:05 AM   #6
sebian
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Quote:
Originally Posted by JohnC7 View Post
I do have a multimeter to test. I guess I'll check for amp draw. I know the voltage from a cigarette lighter outlet. I'm pretty sure it's the alternator. A charge that was once 14.4 is now 13.8. I almost doubt it's the amps for the sound system I have in there since this never happened with my old battery.
It sounds like you are already pretty set on replacing the alternator. It's your money, do as you wish with it. But, imo, you are wasting money until you check the voltage output at the alternator and battery. And I say at both, because there could be a wiring issue going between the battery and alternator.

Checking at the 12v outlet is not a good test. Too many other variables in the way to get a good measurement.
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Unread 09-25-2014, 09:44 AM   #7
PolkaPower
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Watch out for refurbished parts store garbage. I would go to a shop and have it rebuilt before I would buy that stuff. Reliability is worth the money.
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Unread 09-25-2014, 10:08 AM   #8
Uniblurb
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Agree with others your alternator is probably still good and well within the charging specs. To make sure your alternator is putting out all it's capable of make sure all your contacts on the back of it are clean/good. This include the 2 small field terminals in the middle and believe it's the green wire which provides direct feedback to the PCM which tells the alternator when to kick the charging field on/off.

System grounds and the ground for the alternator are also real important. Make sure your 3 engine grounds, 2 on the coil studs and 1 on the oil dipstick tube bracket, are all clean/good. One of the grounds on the coil studs ground the PCM which in turn grounds all the sensors is critical to be good and clean. This has more to do with your whole electrical system functioning properly rather than just the alternator.

The alternator bracket which attaches to the engine block also functions as a ground to the alternator case. I was kind of shocked when I removed mine on my 96 4.0 and found a glaze/varnish on the back of the bracket where it meets the block. Aluminum and steel don't like each other while I cleaned it all off with a wire wheel to make a better ground connection. While probably not necessary I also ran an extra pre-made ground strap from one of the bottom alternator grounding studs to the front stud on the coil bracket. Good luck!
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Unread 09-25-2014, 10:40 AM   #9
HighLonesome
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Quote:
Originally Posted by PolkaPower View Post
Watch out for refurbished parts store garbage. I would go to a shop and have it rebuilt before I would buy that stuff. Reliability is worth the money.
x2 on that!
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Unread 09-26-2014, 11:45 PM   #10
GoneBad
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Battery temperature Sensor

Another thing to consider is the battery temperature sensor (under the battery). The charging system monitors the temperature of the battery and uses it to reduce the charging voltage as the battery temperature increases. Poor contact could result in falsely high temperature readings (and lower charging voltage) if the underhood temperature rises faster than the insulated and heavy battery.

My latest battery has ribs on the bottom and the sensor was not getting good contact. I glued an aluminum spacer between the battery case ribs to allow the sensor to more accurately read the temperature.
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Unread 09-27-2014, 11:41 PM   #11
AVR2
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How to do a parasitic draw test:

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Unread 09-28-2014, 04:17 PM   #12
JohnC7
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So I didn't buy a alternator. But right now as I speak I have a multimeter hook up to the negative connector and post to see amp draw. On the 10 amp setting it's reading 3.31 amps and I am going through each relay and fuse.
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Unread 09-28-2014, 04:24 PM   #13
JohnC7
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I pulled the fuses under the hood. The two fuses that drop to .3 amps was 7 (ignition off draw, fuses 13,16,19,20,21 in fuse panel, circuit breaker in cavity 3 of fuse panel) and 11 ( memory functions, power windows, remote key less entry, trailer towing).
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Unread 09-28-2014, 04:30 PM   #14
JohnC7
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Panel on passenger side fuses 16(courtesy lights) dropped by 3 amps and fuse 21 ( power outlet) dropped by .3

Edit: sorry for all the posts.
I had a battery tender quick connect installed and I removed it and went down to 2.6 amps
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Unread 10-01-2014, 12:45 PM   #15
sebian
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Sounds like you are at the fun point. You will probably need to get a wiring diagram to see if there is a common point for all of those circuits. There might be a switch somewhere that links everything together. In this case, possibly your interior light switch might be at fault.

Edit: It would make sense for there to be high draw if you did not depress the light switch on the door jam while testing. And it could also be one of the other door switches causing the problem.
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List of parts not replaced yet:
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