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-   -   Battery gauge low, check engine light on (http://www.wranglerforum.com/f218/battery-gauge-low-check-engine-light-on-71215.html)

bjwalsh 12-05-2010 09:47 PM

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.

NAVYCHIEF 12-05-2010 09:53 PM

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?

hannahuffster 12-05-2010 09:55 PM

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...

bjwalsh 12-05-2010 11:12 PM

@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.

MikeMTJ 12-05-2010 11:17 PM

It won't ever get 19 mpg. I get 13, and my engine only has 57k on it.

NAVYCHIEF 12-06-2010 01:06 AM

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.

wranglerYJnewb 12-06-2010 01:20 AM

Quote:

Originally Posted by bjwalsh (Post 910144)
@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

bjwalsh 12-06-2010 11:54 AM

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 12-06-2010 03:09 PM

Quote:

Originally Posted by NAVYCHIEF (Post 910033)
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.

hannahuffster 12-06-2010 03:09 PM

I get right @ 13 mpg on my 93 2.5 with 33" bfg km2's & she runs like a top...

hannahuffster 12-06-2010 03:11 PM

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...

hannahuffster 12-06-2010 03:13 PM

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...

bjwalsh 12-06-2010 03:30 PM

Quote:

Originally Posted by hannahuffster (Post 910872)
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.

hannahuffster 12-06-2010 04:36 PM

I would guess the alternator. If the battery is starting the jeep is is probably ok.

ISUSteve 12-06-2010 05:34 PM

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

hannahuffster 12-06-2010 05:51 PM

Quote:

Originally Posted by ISUSteve (Post 911100)
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.

bjwalsh 12-07-2010 12:08 AM

Quote:

Originally Posted by hannahuffster (Post 911143)
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 12-07-2010 07:19 PM

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?

NAVYCHIEF 12-07-2010 07:44 PM

where was the fuse located? by brake pedal or under the hood?

bjwalsh 12-07-2010 08:08 PM

Quote:

Originally Posted by NAVYCHIEF (Post 912883)
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 12-07-2010 08:39 PM

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 12-08-2010 01:19 AM

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 12-08-2010 12:09 PM

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.

Garyk 12-08-2010 02:29 PM

Time to invest in a new battery


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