Reversed Polarity on Battery Install - Now Battery Doesn't Charge - 1989 Cherokee - JeepForum.com
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Unread 01-16-2014, 10:26 AM   #1
jonnymilano
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Reversed Polarity on Battery Install - Now Battery Doesn't Charge - 1989 Cherokee

Let's get this out of the way: I may be one of the dumbest people to work on a vehical, ever. Yep, I installed a battery backwards.

I recently bought a 1989 Cherokee with the intention of fixing/tuning it up. Things were going well until I replaced the battery in the dark. The new battery had the posts reversed on the other side compaired to the old one and I installed it backwards!!!

A few seconds after I conected the terminals, a blue wire on what I think is the starter relay blew up, shot sparks and looked like it was going to catch on fire. I obviously freaked, ripped the terminal off of the battery and said the F word a lot. The mysterious rectangular box with a bunch of wires connected to it lives mounted to a bracket with two screws. It sits pretty close to the battery and the secondary hot wire goes directly from the battery to top of it. The blue wire that is connected to the box (which I think is the starter relay) more than likely leads to the alternator. I can follow it visually with a group of wires to a junction where one way leads to the alternator.

After I installed the battery correctly, patched up the blue wire, and replaced all of the fuses (none were blown but did it anyway) I tried starting the Jeep and to my amazement, it started fine! Everything electrical worked! However, after driving it a little I realized that the battery wasn't charging. After about 3-4 starts it didn't have enough juice to turn over. Busted out the multimeter to confirm. Yep, dying battery. Put a fresh battery in, measured the voltage (12.5 with Jeep off), ran the engine and voltage dropped by about 1 volt. I know that voltage should go up by about 2 volts with the jeep on, so figured that I had fried the alternator with the battery incident. Replaced the alternator last night. Expected it to work, but same effect - no chargey battery!

So, kinda at a loss here. I don't know much about working on electrical systems. Why isn't the battery charging? Should I replace what I think is the starter relay? Is there a better way to tell what blew up? Is there a computer on this vintage and where would it be and how much does it cost? Is it "easy" to replace the starter relay?

I don't really want to take it to the stealership for a diagnostic(?), but may have to at this point because I can't think of what is broken. I'm mad at myself, I did the usual tune up stuff (fuel filter, throttle body clean, sparkplugs) and she was running pretty good. Now this... Thanks in advance for the help!

PS manual transmission and no ABS.


Last edited by jonnymilano; 01-16-2014 at 10:57 AM.. Reason: Realized I was using the wrong terminology.
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Unread 01-16-2014, 11:40 AM   #2
CCKen
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Quote:
Originally Posted by jonnymilano View Post
Let's get this out of the way: I may be one of the dumbest people to work on a vehical, ever. Yep, I installed a battery backwards.

I recently bought a 1989 Cherokee with the intention of fixing/tuning it up. Things were going well until I replaced the battery in the dark. The new battery had the posts reversed on the other side compaired to the old one and I installed it backwards!!!

A few seconds after I conected the terminals, a blue wire on what I think is the starter relay blew up, shot sparks and looked like it was going to catch on fire. I obviously freaked, ripped the terminal off of the battery and said the F word a lot. The mysterious rectangular box with a bunch of wires connected to it lives mounted to a bracket with two screws. It sits pretty close to the battery and the secondary hot wire goes directly from the battery to top of it. The blue wire that is connected to the box (which I think is the starter relay) more than likely leads to the alternator. I can follow it visually with a group of wires to a junction where one way leads to the alternator.

After I installed the battery correctly, patched up the blue wire, and replaced all of the fuses (none were blown but did it anyway) I tried starting the Jeep and to my amazement, it started fine! Everything electrical worked! However, after driving it a little I realized that the battery wasn't charging. After about 3-4 starts it didn't have enough juice to turn over. Busted out the multimeter to confirm. Yep, dying battery. Put a fresh battery in, measured the voltage (12.5 with Jeep off), ran the engine and voltage dropped by about 1 volt. I know that voltage should go up by about 2 volts with the jeep on, so figured that I had fried the alternator with the battery incident. Replaced the alternator last night. Expected it to work, but same effect - no chargey battery!

So, kinda at a loss here. I don't know much about working on electrical systems. Why isn't the battery charging? Should I replace what I think is the starter relay? Is there a better way to tell what blew up? Is there a computer on this vintage and where would it be and how much does it cost? Is it "easy" to replace the starter relay?

I don't really want to take it to the stealership for a diagnostic(?), but may have to at this point because I can't think of what is broken. I'm mad at myself, I did the usual tune up stuff (fuel filter, throttle body clean, sparkplugs) and she was running pretty good. Now this... Thanks in advance for the help!

PS manual transmission and no ABS.
My 2 cents:

You cooked the alternator. Take it to a shop and have it tested.
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Unread 01-16-2014, 12:42 PM   #3
jonnymilano
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Thanks, I will do that. I've already installed a new one though. I think the 'wire' to the starter relay was a fusible link that is still not conducting. I guess that I will try replacing that. Does anyone have a good YouTube tutorial on replacing fusible links? I'm brand new at it. Thanks.
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Unread 01-16-2014, 01:10 PM   #4
CCKen
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Quote:
Originally Posted by jonnymilano View Post
Thanks, I will do that. I've already installed a new one though. I think the 'wire' to the starter relay was a fusible link that is still not conducting. I guess that I will try replacing that. Does anyone have a good YouTube tutorial on replacing fusible links? I'm brand new at it. Thanks.
That Blue wire sounds like a fusible link.

Go here and read about fusible links. They also show repair links available.

http://www.whiteproducts.com/fusible-faqs.shtml

I don't have a Youtuibe link for you.
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Unread 01-16-2014, 01:38 PM   #5
uberxj92
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Isn't the alternator on the renix a GM? You may have popped the fuse able link that goes there.
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Unread 01-17-2014, 11:08 AM   #6
jonnymilano
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CCKen, thanks for the info!

uberxj92, in the end it was indeed a $1.05 fusible link all along! I feel like a dummy - guess I'm still learning.. All I had to do was replace the blue 'wire' (fusible link) that fed juice from the alt to the battery. I thought that I had replaced it with a wire, to just test if it was working, but turns out it was a 12" link and ran out of sight (so it was still burnt out). Man, don't I feel stupid. Replaced that link and she's working again! The 26 year old Jeep lives!

As an aside, I have no idea if the alternator is a GM or not. I guess I should hold on to the old one as it's still good. Do you know if it will fit in a lot of vehicles? I'm loving the XJ platform. Will it fit in most of those?

Thanks all for the help!!!

Last edited by jonnymilano; 01-17-2014 at 11:09 AM.. Reason: typ-o
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Unread 01-17-2014, 11:41 AM   #7
CCKen
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Quote:
Originally Posted by jonnymilano View Post
CCKen, thanks for the info!

uberxj92, in the end it was indeed a $1.05 fusible link all along! I feel like a dummy - guess I'm still learning.. All I had to do was replace the blue 'wire' (fusible link) that fed juice from the alt to the battery. I thought that I had replaced it with a wire, to just test if it was working, but turns out it was a 12" link and ran out of sight (so it was still burnt out). Man, don't I feel stupid. Replaced that link and she's working again! The 26 year old Jeep lives!

Good work, and thanks for the follow up.

As an aside, I have no idea if the alternator is a GM or not. I guess I should hold on to the old one as it's still good. Do you know if it will fit in a lot of vehicles? I'm loving the XJ platform. Will it fit in most of those?

Thanks all for the help!!!
Hang on to that alternator.

Here's a list of alternator part numbers, by year:

Alternator Part Numbers

1988-1990

JR775127
60 Ampere

JR775126
85 Ampere

53002898
85 Ampere Export

JR775125
100 Ampere

53002897
100 Ampere Export

1991-1993

56005685
90 Ampere

1994-1996

56005685
90 Ampere

56026811
117 Ampere

1997-1998

56005685AB
56026936

1999-2001

56041822AA
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Unread 01-17-2014, 12:00 PM   #8
jonnymilano
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Thanks again, CCKen! That's awesome!
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