New alternator needed? Or something more? - JeepForum.com
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post #1 of 17 Old 04-12-2016, 06:34 PM Thread Starter
ZAM97
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New alternator needed? Or something more?

Hey all,
Ive been having some issues with my 97' Sahara.
I suspect there is some electrical problem; as I apply gas, the RPMs fluctuate, resulting in my Jeep lurching down the street in max first gear. It even occasionally shuts off while idling, and the engine feels like its not running at 'full power'. Ive recently put in a new computer and a new CPS, so Im running out of ideas here.

New alternator? New battery?

Im thinking that the alternator probably needs to be replaced; Ive heard that a faulty alternator can drain the battery very fast due it bypassing the alternator and drawing power right off the battery itself. This may be causing a general power failure? Any ideas?

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post #2 of 17 Old 04-12-2016, 06:38 PM
SouthernGypsy
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If you have a multi-tester you should be able to test, put your leads on the battery and take a reading without the Jeep running (and all accessories off), make sure it's at least 12.4 volts or more. Then start it. See if the voltage increases, it should go up to somewhere in the 14 volt range. Have someone vary the throttle, the voltage shouldn't "jump around", it will naturally vary a little with engine speed, but nothing wild.

You can also take it to a parts store who has a battery load-tester and can test your battery to see how well it's doing.
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post #3 of 17 Old 04-12-2016, 07:47 PM
chevy2169
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Quote:
Originally Posted by ZAM97
Hey all, Ive been having some issues with my 97' Sahara. I suspect there is some electrical problem; as I apply gas, the RPMs fluctuate, resulting in my Jeep lurching down the street in max first gear. It even occasionally shuts off while idling, and the engine feels like its not running at 'full power'. Ive recently put in a new computer and a new CPS, so Im running out of ideas here. New alternator? New battery? Im thinking that the alternator probably needs to be replaced; Ive heard that a faulty alternator can drain the battery very fast due it bypassing the alternator and drawing power right off the battery itself. This may be causing a general power failure? Any ideas?
Is the battery light on the dash?

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post #4 of 17 Old 04-12-2016, 11:28 PM
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Start simple, CLEAN the battery terminals. Lots of weird things happen when these trucks have dirty battery connections. There have been cases of internal corrosion on the battery cables wrecking havok as well.


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post #5 of 17 Old 04-13-2016, 06:16 AM
billdacat
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Stop throwing parts at it and get yourself a good multimeter. (learn how to use it) Clean and or replace degraded wiring connections.
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post #6 of 17 Old 04-13-2016, 07:03 AM
JStMarie
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Quote:
Ive recently put in a new computer and a new CPS, so Im running out of ideas here.
I'm not clear, was this in an attempt to fix this RPM issue or did the current problem start after replacing the computer and/or cps?

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post #7 of 17 Old 04-13-2016, 08:02 AM
bobjp
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Yeah, things are backward here. There are a number of things I would do before replacing a computer or CPS.

Is the engine light on and if so, what are the codes?

Did you check the spark plugs, wires, cap, and rotor?

Vacuum leaks?

Upstream O2 sensor? Disconnect it, see what happens.

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post #8 of 17 Old 04-14-2016, 02:21 PM Thread Starter
ZAM97
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The main issue now is my vehicle's inability start properly and its questionable ability to STAY running. This is 100% a electrical issue; and a very serious one at that, at least if this persists. To answer that one fellow's question, my error codes were 11 and 12, but those have been addressed. There are no error lights on at all.

I know the alternator I have in there is old; its also the only thing I haven't fixed on that car's electrical system. This issue is causing the car to run directly off the battery and I feel the difference now. The lights are dimmer inside the car and out, my ignition and idle are 'weaker' that usual, it chugs on startup, and it sometimes dies when coming to a stop... and only the little baby Jesus knows if it will start up again that time.

In the process of coming to these conclusions, Ive run the battery dry twice now and have needed to charge it up again, which is probably torture o the battery itself. If the alternator isnt causing this, then what is?
In the interest of not further messing anything up an already-messed up electrical system, Im going to get a new alternator and see what happens. I see some good prices online and Ive replaced an alternator before, on another Jeep I once owned.
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post #9 of 17 Old 04-14-2016, 04:27 PM
98TJSE
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why keep throwing parts at it.. do some actual diagnostics..

alternator would be easy to test, vehicle should run a while on a good battery without charging system.

the cps you replaced could be issue if its not OEM part.. jeeps tend to hate aftermarket parts store parts

IAS , idle air sensor could be bad, dirty or so on, could be dirty throttle body

have you actually tested output voltage? multi meter is cheap, also if voltage was issue light would be on..

maybe the PCM you poppedin is defective or not proper one..

i would charge battery and get it load tested..

i would swap cps is its not OEM .
and as stated above many other thing to test to determine the issue but i would test voltage first before getting a new alternator
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post #10 of 17 Old 04-14-2016, 04:37 PM
bobjp
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^^^What he said. Stop throwing parts. Do diagnostics.

For the love of pete, measure the voltage at the battery while it's running. Why you would consider replacing the battery or the alternator without doing this basic step is beyond me. What does the gauge on the dash show? Is the battery light on?

Cheap volt meters can be had at discount tool stores. Autozone will measure voltage at the store for you. They will also test the alternator if you pull it out of the Jeep.


You never mention cleaning the alternator connection. Why wouldn't you do this if you suspect you have a charging issue?


People are giving you solid advice and concise direction that you aren't paying any attention to.

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post #11 of 17 Old 04-14-2016, 05:51 PM Thread Starter
ZAM97
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Originally Posted by bobjp View Post
^^^What he said. Stop throwing parts. Do diagnostics.

For the love of pete, measure the voltage at the battery while it's running. Why you would consider replacing the battery or the alternator without doing this basic step is beyond me. What does the gauge on the dash show? Is the battery light on?

Cheap volt meters can be had at discount tool stores. Autozone will measure voltage at the store for you. They will also test the alternator if you pull it out of the Jeep.


You never mention cleaning the alternator connection. Why wouldn't you do this if you suspect you have a charging issue?


People are giving you solid advice and concise direction that you aren't paying any attention to.
bc I am having trouble explaining the complicated history of this vehicle. Ive had it for years, but this is the first time Im truly stumped.

I came here for advice, which Im getting a lot of. I made sure the CPS was compatible, and it is. Some of these other basic things Ive already done; Ive load tested the battery and it indicates its good for now and Ive cleaned the areas. The gauge is at about the quarter line, when running solely off the battery. All signs point to a new alternator being needed, regardless of whether or not it will fix all the issues.

If Im not being clear enough and you want more info, just say it, albeit a bit nicer.
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post #12 of 17 Old 04-14-2016, 05:53 PM
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Quote:
Originally Posted by ZAM97 View Post
bc I am having trouble explaining the complicated history of this vehicle. Ive had it for years, but this is the first time Im truly stumped.

I came here for advice, which Im getting a lot of. I made sure the CPS was compatible, and it is. Some of these other basic things Ive already done; Ive load tested the battery and it indicates its good for now and Ive cleaned the areas. The gauge is at about the quarter line, when running solely off the battery. All signs point to a new alternator being needed, regardless of whether or not it will fix all the issues.

If Im not being clear enough and you want more info, just say it, albeit a bit nicer.
What is your alternators voltage output?
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post #13 of 17 Old 04-14-2016, 06:08 PM
bobjp
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Quote:
Originally Posted by ZAM97 View Post
bc I am having trouble explaining the complicated history of this vehicle. Ive had it for years, but this is the first time Im truly stumped.

I came here for advice, which Im getting a lot of. I made sure the CPS was compatible, and it is. Some of these other basic things Ive already done; Ive load tested the battery and it indicates its good for now and Ive cleaned the areas. The gauge is at about the quarter line, when running solely off the battery. All signs point to a new alternator being needed, regardless of whether or not it will fix all the issues.

If Im not being clear enough and you want more info, just say it, albeit a bit nicer.
There's your answer, your alternator is probably bad. Although, I'm guess as to what you call the "1/4 line" because there isn't one.

It's not hard to help people when they actually provide information about their problem. Nobody can possibly tell the condition of an alternator without knowing it's voltage output.


You never had a bad CPS or computer. You threw parts at the problem instead of looking at the gauge on the dash.

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post #14 of 17 Old 04-15-2016, 12:56 PM
JStMarie
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I think the bottom line here is if you expect quality help you need to provide quality information. I'm very unclear on what "the gauge is at about the quarter line" means and I am very confused when you say something like "when running solely off the battery". Does this mean you have the alternator disconnected or does it mean you are assuming the alternator isn't charging?

Stick with the facts as things are now. Providing history without a the slant on what you might think it is can be very helpful as well. You wouldn't be here asking questions if you knew what it is because if that were the case it would be fixed already.

If we accept your word that this is an electrical issue then the simplest and really most effective thing to do right now is to check the battery voltage with a multi meter while the vehicle is running with the leads on the battery terminals. This will tell us whether you are getting sufficient charge, which ought to be 14.3 to 14.8 volts or so in my experience. lower than 14 volts and you definitely have a charging problem. That charging problem may or may not be the alternator, but we aren't there yet.

A good diagnostician goes into his job assuming nothing and lets the facts, as he gathers them, dictate his next action.

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post #15 of 17 Old 04-15-2016, 02:06 PM
bobjp
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Typical voltage is closer to 13.8-14.2. Less than 14 isn't necessarily bad.

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