Battery gauge low, check engine light on - Jeep Wrangler Forum
Jeep Wrangler Forum

Go Back   Jeep Wrangler Forum > YJ Jeep Wrangler Forum > YJ Tech Forum

Join Wrangler Forum Today


Reply
 
Thread Tools

Please support our sponsors and let them know you heard about them on WranglerForum.com
Old 12-05-2010, 09:47 PM   #1
Newb
 
Join Date: Dec 2010
Posts: 11
Battery gauge low, check engine light on

I have a 91 Wrangler, approx. 175k miles. Recently replaced the fuel pump and belt. Just ran out of gas (to my dismay discovered I only get about 200 miles on a 15 gallon tank, but that's beside the point). Now the "check engine" light comes on after a few miles and the battery gauge is showing pretty low. Checked the battery with a multimeter and it shows 12 volts. Not sure what to check. Alternator? Any help would be appreciated.

bjwalsh is offline   Quote Quick Reply
Old 12-05-2010, 09:53 PM   #2
Jeeper
 
NAVYCHIEF's Avatar
 
Join Date: Sep 2008
Posts: 2,207
i had the same thing happen. i took the alternator apart and cleaned the armature with emery cloth and reassembled it. never had that problem since. been about a year. haynes manual has directions on how to take it apart. what code are you getting?

__________________
1994 RENEGADE

TREAT EVERY STRESSFUL SITUATION AS A DOG WOULD.
IF YOU CAN'T EAT IT OR PLAY WITH IT,
JUST PEE ON IT AND WALK AWAY.
NAVYCHIEF is offline   Quote Quick Reply
Old 12-05-2010, 09:55 PM   #3
Jeeper
 
hannahuffster's Avatar
 
Join Date: Mar 2010
Location: Joplin, MO
Posts: 402
Images: 1
Is the motor running or idling rough when the voltage (it is reading alternator volts not the batteries volts) meter is reading low? If the motor is running rough it will most likely be reading low voltage because the alternator is turning slower than it should be. check for slack / play in your new belt. Does it sqawk or squall like it is slipping?

hey over 13 mpg aint bad in an old jeep...
__________________
J&D OFF-ROAD CLUB CHARTER MEMBER #10 OF S.W. MO [/CENTER]
hannahuffster is offline   Quote Quick Reply
Old 12-05-2010, 11:12 PM   #4
Newb
 
Join Date: Dec 2010
Posts: 11
@NAVYCHIEF: Don't have anything to tell me the code. Will look into servicing the alternator if nothing else comes up. Thanks.

@hannahuffster: No, not running rough. Checked the belt - it is nice and tight - no play or slack. Was hoping for a little better mileage with the 4 cylinder. My 4 cyl. toyota truck gets 19 MPG.
bjwalsh is offline   Quote Quick Reply
Old 12-05-2010, 11:17 PM   #5
Jeeper
 
MikeMTJ's Avatar
 
Join Date: Nov 2009
Location: If only I knew....
Posts: 2,113
Send a message via AIM to MikeMTJ
It won't ever get 19 mpg. I get 13, and my engine only has 57k on it.
MikeMTJ is offline   Quote Quick Reply
Old 12-06-2010, 01:06 AM   #6
Jeeper
 
NAVYCHIEF's Avatar
 
Join Date: Sep 2008
Posts: 2,207
bj, the codes are read by following the proceedures in my first note above. all you do is turn the key on and off as described above and count the number of times the light flashes. when i did mine the flashes indicated 41 which is the field voltage of the alternator was low.
__________________
1994 RENEGADE

TREAT EVERY STRESSFUL SITUATION AS A DOG WOULD.
IF YOU CAN'T EAT IT OR PLAY WITH IT,
JUST PEE ON IT AND WALK AWAY.
NAVYCHIEF is offline   Quote Quick Reply
Old 12-06-2010, 01:20 AM   #7
Jeeper
 
Join Date: Feb 2010
Posts: 419
Quote:
Originally Posted by bjwalsh View Post
@NAVYCHIEF: Don't have anything to tell me the code. Will look into servicing the alternator if nothing else comes up. Thanks.

@hannahuffster: No, not running rough. Checked the belt - it is nice and tight - no play or slack. Was hoping for a little better mileage with the 4 cylinder. My 4 cyl. toyota truck gets 19 MPG.
hmmm i have a 93 2.5L and she gets consistently 16.5 mpg ... I did th 20g mod and get around 325-335 miles a tank
wranglerYJnewb is offline   Quote Quick Reply
Old 12-06-2010, 11:54 AM   #8
Newb
 
Join Date: Dec 2010
Posts: 11
Quote:
bj, the codes are read by following the proceedures in my first note above. all you do is turn the key on and off as described above and count the number of times the light flashes. when i did mine the flashes indicated 41 which is the field voltage of the alternator was low.
Sorry, didn't read far enough. That's very handy to know. Will check the codes tonight. Thanks for the info.
bjwalsh is offline   Quote Quick Reply
Old 12-06-2010, 03:09 PM   #9
Newb
 
Join Date: Dec 2010
Posts: 11
Quote:
Originally Posted by NAVYCHIEF View Post
i had the same thing happen. i took the alternator apart and cleaned the armature with emery cloth and reassembled it. never had that problem since. been about a year. haynes manual has directions on how to take it apart. what code are you getting?
Ok, I checked (and re-checked) the codes. Some weird results. Here's what I got:

12 - ?
33 (Air conditioning clutch relay) - strange since I don't have an air conditioner
47 (Battery under voltage) - expected

I thought maybe I had screwed up the first couple codes, but got the same numbers when I checked again.
bjwalsh is offline   Quote Quick Reply
Old 12-06-2010, 03:09 PM   #10
Jeeper
 
hannahuffster's Avatar
 
Join Date: Mar 2010
Location: Joplin, MO
Posts: 402
Images: 1
I get right @ 13 mpg on my 93 2.5 with 33" bfg km2's & she runs like a top...
__________________
J&D OFF-ROAD CLUB CHARTER MEMBER #10 OF S.W. MO [/CENTER]
hannahuffster is offline   Quote Quick Reply
Old 12-06-2010, 03:11 PM   #11
Jeeper
 
hannahuffster's Avatar
 
Join Date: Mar 2010
Location: Joplin, MO
Posts: 402
Images: 1
You got a 55 at the end too right? I always get the ac clutch when I trouble code mine (and I have not AC too). I would say that 47 is the trouble...
__________________
J&D OFF-ROAD CLUB CHARTER MEMBER #10 OF S.W. MO [/CENTER]
hannahuffster is offline   Quote Quick Reply
Old 12-06-2010, 03:13 PM   #12
Jeeper
 
hannahuffster's Avatar
 
Join Date: Mar 2010
Location: Joplin, MO
Posts: 402
Images: 1
47** Battery voltage sense input below target charging voltage during engine operation. Also, no significant change detected in battery voltage during active test of generator output. -- will trigger check light...
__________________
J&D OFF-ROAD CLUB CHARTER MEMBER #10 OF S.W. MO [/CENTER]
hannahuffster is offline   Quote Quick Reply
Old 12-06-2010, 03:30 PM   #13
Newb
 
Join Date: Dec 2010
Posts: 11
Quote:
Originally Posted by hannahuffster View Post
You got a 55 at the end too right? I always get the ac clutch when I trouble code mine (and I have not AC too). I would say that 47 is the trouble...
Yes, got the 55 at the end. So looks like either the battery or alternator then. This all started after running out of gas and running the headlights and emergency lights off battery while waiting for AAA. First time I ran the battery that low.
bjwalsh is offline   Quote Quick Reply
Old 12-06-2010, 04:36 PM   #14
Jeeper
 
hannahuffster's Avatar
 
Join Date: Mar 2010
Location: Joplin, MO
Posts: 402
Images: 1
I would guess the alternator. If the battery is starting the jeep is is probably ok.
__________________
J&D OFF-ROAD CLUB CHARTER MEMBER #10 OF S.W. MO [/CENTER]
hannahuffster is offline   Quote Quick Reply
Old 12-06-2010, 05:34 PM   #15
Jeeper
 
Join Date: Nov 2010
Posts: 74
12 is the start sequence, but you hardly ever see it listed.
33 is normal if you have no ac.

is your battery and terminals clean
ISUSteve is offline   Quote Quick Reply
Old 12-06-2010, 05:51 PM   #16
Jeeper
 
hannahuffster's Avatar
 
Join Date: Mar 2010
Location: Joplin, MO
Posts: 402
Images: 1
Quote:
Originally Posted by ISUSteve View Post
12 is the start sequence, but you hardly ever see it listed.
33 is normal if you have no ac.

is your battery and terminals clean
incorrect - 12* Direct battery input to PCM was disconnected within the last 50 key-on cycles -- and doesn not trigger check lamp.
__________________
J&D OFF-ROAD CLUB CHARTER MEMBER #10 OF S.W. MO [/CENTER]
hannahuffster is offline   Quote Quick Reply
Old 12-07-2010, 12:08 AM   #17
Newb
 
Join Date: Dec 2010
Posts: 11
Quote:
Originally Posted by hannahuffster View Post
incorrect - 12* Direct battery input to PCM was disconnected within the last 50 key-on cycles -- and doesn not trigger check lamp.
Good to know. Had it in the shop not too long ago to replace the fuel pump, so that would explain that code. Battery is perfectly clean. Looking like the alternator. Going to replace it tomorrow.
bjwalsh is offline   Quote Quick Reply
Old 12-07-2010, 07:19 PM   #18
Newb
 
Join Date: Dec 2010
Posts: 11
Replaced the alternator (old one had lifetime warranty, so free!). Unfortunately didn't fix the problem. Finally decided to check the fuses (should have done this first, but I'm still learning). The one labelled "ALT PWR 2" was blown. Thought I had found the problem, but replaced the fuse, started it up and minute later - pop. Fuse blown again.

I'm pretty sure I got the right alternator. So perhaps a grounded wire coming from the alternator?
bjwalsh is offline   Quote Quick Reply
Old 12-07-2010, 07:44 PM   #19
Jeeper
 
NAVYCHIEF's Avatar
 
Join Date: Sep 2008
Posts: 2,207
where was the fuse located? by brake pedal or under the hood?
__________________
1994 RENEGADE

TREAT EVERY STRESSFUL SITUATION AS A DOG WOULD.
IF YOU CAN'T EAT IT OR PLAY WITH IT,
JUST PEE ON IT AND WALK AWAY.
NAVYCHIEF is offline   Quote Quick Reply
Old 12-07-2010, 08:08 PM   #20
Newb
 
Join Date: Dec 2010
Posts: 11
Quote:
Originally Posted by NAVYCHIEF View Post
where was the fuse located? by brake pedal or under the hood?
Under the hood. According to the wiring diagram the alternator is connected to that fuse.
bjwalsh is offline   Quote Quick Reply
Old 12-07-2010, 08:39 PM   #21
Newb
 
Join Date: Dec 2010
Posts: 11
I'm starting to think that maybe I did get the wrong alternator. I examined the test report that came with it and it says it's a 90 amp alternator. The output at 2500 RPM is 63 amps. Since the fuse is only 50 amps and I don't see anything that would be stepping down the amperage it seems logical that the alternator is putting out too much power.

BTW, the fuse blows when I rev the engine.
bjwalsh is offline   Quote Quick Reply
Old 12-08-2010, 01:19 AM   #22
Newb
 
Join Date: Dec 2010
Posts: 11
Am I over-simplifying this? The alternator is supposed to be computer-controlled. Is is possible the computer (wherever that is) is faulty and not controlling the amperage from the alternator?
bjwalsh is offline   Quote Quick Reply
Old 12-08-2010, 12:09 PM   #23
Newb
 
Join Date: Dec 2010
Posts: 11
Sorry for all the noob posts, I'm new to this stuff. I've been doing some googling on this and found some posts on other forums suggesting a drained (or bad) battery could cause the alternator to output the full 90 amps, which blows the 50 amp maxi fuse. My battery is definitely low. Any idea if putting it on a charger first would avoid blowing the fuse? Seems strange that a drained battery could cause that.
bjwalsh is offline   Quote Quick Reply
Old 12-08-2010, 02:29 PM   #24
Jeeper
 
Join Date: Jan 2010
Location: Las Cruces, NM
Posts: 2,291
Time to invest in a new battery

__________________
2013 WRANGLER SPORT 2 DR., V-6 ,AUTO,HARD TOP
(Sold)1994 Jeep Wrangler 2.5L, Bestop top
/w steel half door and slider windows
5 speed, 2.5" lift, 31" tires,rack lights
Garyk is offline   Quote Quick Reply
Reply

Tags
"check engine" , battery , wrangler

Quick Reply
Message:
Options

Register Now

In order to be able to post messages on the Jeep Wrangler Forum forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.
User Name:
If you do not want to register, fill this field only and the name will be used as user name for your post.
Password
Please enter a password for your user account. Note that passwords are case-sensitive.
Password:
Confirm Password:
Email Address
Please enter a valid email address for yourself.
Email Address:

Log-in

Human Verification

In order to verify that you are a human and not a spam bot, please enter the answer into the following box below based on the instructions contained in the graphic.



Thread Tools

Posting Rules
You may post new threads
You may post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
check engine light tbowden91 YJ Tech Forum 28 03-07-2014 10:20 PM
Check engine light the old guy TJ Tech Forum 3 11-25-2010 02:41 PM
Check Engine Light? Dewry636 TJ Tech Forum 0 10-29-2010 04:31 PM
check engine light? NEED HELP shorty8914446 TJ Tech Forum 4 03-08-2010 04:26 PM
Idling strange = check engine light? Rubigoddess TJ Tech Forum 6 03-01-2008 12:38 PM


» Rates
Get low rates on auto insurance in Canada!

» Network Links
»Jeep Parts
» Featured Product

All times are GMT -5. The time now is 11:59 PM.



Jeep®, Wrangler, Liberty, Wagoneer, Cherokee, and Grand Cherokee are copyrighted and trademarked to Chrysler Motors LLC.
Wranglerforum.com is not in any way associated with the Chrysler Motors LLC