Alternator fusible link issue

Tiny
IVARCJ
  • MEMBER
  • 2012 JEEP GRAND CHEROKEE LAREDO
  • 3.6L
  • V6
  • 4WD
  • AUTOMATIC
  • 116,000 MILES
Hi. I had a lightning bolt symbol go on in my vehicle listed above Grand Cherokee. Shortly after all the gauge cluster went wacky. Started getting a bunch of codes popping up randomly and even the wipers cycled once then the vehicle shut off as I was leaving my driveway. I took out the battery then charged it properly, took it to Napa and after being tested they said it was still good (700cca tested around 660cca). I took it back home and put it in my vehicle and the lightning bolt symbol went away but was followed by a battery symbol. The vehicle did start but the light remained so I put my battery charger on it and tested the alternator which showed to be bad (160amp alt). So I purchased an upgraded alt (240 amp) and installed it. Jeep started but still got the battery light so I ran a voltage test with my charger and it wasn't charging. I took the old alt at this point to Napa to see if it was something to do with my alt. The old alternator tested fine. I used a test light on the output side of the new installed alternator and got ( no light) which told me the alt was fine but wasn't getting input signal voltage. So I started tracing the wire up the front of the engine and noticed it was burned. After unraveling the tape and wire loom I noticed the fusible link was burned. I cut all the bad link out and jumped a ( heavy gauge) wire across where the fusible link once was and started the vehicle and ran a voltage and alt test. Everything tested fine this time around so here is where my concern starts. After turning off the vehicle I felt the jumper and other pieces of cable it was temporarily attached to and they were all very warm to the touch( not hot but very warm) I only had the vehicle running a couple minutes to run the voltage and alternator test. So my question is, can I just run another fusible link in that place where the other burned? And if so what type am I looking at getting? Also it worries me that the wires where the fusible link had previously blown are getting very warm. So my next question is, could there be an underlying problem that caused the link to blow in the first place? Everything thus far in the vehicle is stock and no wiring has changed or been modified. The radio is stock as well or can I just replace the fusible link, heat shrink it and put electrical tape and the wire loom back on and go about my life or should I be looking for something else? Thanks for your time and sorry for the long novel, I just wanted to be sure you had all the info leading to my problem. Thanks again.
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Monday, June 22nd, 2020 AT 9:18 PM

11 Replies

Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 110,068 POSTS
Hi,

Do me a favor. Disconnect the battery and check the fusible link (what's left of it) for continuity to ground. Something doesn't sound right with this. That wire shouldn't have gotten hot.

Now, I attached a pic below showing the charging system. Identify which wire you found melted.

Next, the voltage regulator for this vehicle is an integral component in the power-train control module (PCM). When you put things together, where did you check if it was charging? Was it at the battery or at the alternator? What were the results?

Note: Be careful placing a heavy gauge wire in place of the fusible link. That can cause a fire if the circuit is overloaded.

Let me know.
Joe
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Monday, June 22nd, 2020 AT 9:28 PM
Tiny
IVARCJ
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  • 8 POSTS
Holy cow! I wasn't expecting that quick of a response. I figured I'd post my question and call it a night. It's 11:00 pm here but I absolutely appreciate the fast response. I went back outside to take a couple more pics. The fusible link was burnt and already disconnected when I discovered it so I just finished taking it off and used the jumper in its place temporarily while testing. I checked for voltage at the battery posts given in the engine bay as the battery is located under the passenger seat and 2 extra posts are available in the engine bay specifically for jump starting. Tests went as follows from the post with car off 12.3v and with the car running was testing at 12.9v with my multi-meter. The wire is brown with a red stripe I believe and is coming directly from the alternator output screw. It could be tan also with a red stripe but it's hard to tell and it runs up under the air intake at the front/top of the engine, from the alt on the pass side toward the driver side and back behind the engine.
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Monday, June 22nd, 2020 AT 10:06 PM
Tiny
IVARCJ
  • MEMBER
  • 8 POSTS
Here is where I tested for voltage (fingers pointing to the posts).
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Monday, June 22nd, 2020 AT 10:08 PM
Tiny
IVARCJ
  • MEMBER
  • 8 POSTS
Here is what was left of what I believe to be the fusible link (finger pointing where it was initially blown/separated).
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Monday, June 22nd, 2020 AT 10:09 PM
Tiny
IVARCJ
  • MEMBER
  • 8 POSTS
Here is where the (fusible link) was blown. And where I later placed the jumper across to test.
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Monday, June 22nd, 2020 AT 10:14 PM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 110,068 POSTS
Wow! There isn't anything left to the insulation. If you follow that, does it go to one of the jumper points? Also, see if you can confirm a color. Take a look at the attached pic and let me know if you feel it is number 1 or 2 in the pic. I believe 2 is the fusible link.
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Monday, June 22nd, 2020 AT 10:49 PM
Tiny
IVARCJ
  • MEMBER
  • 8 POSTS
No, there wasn't much left it was all melted but as soon as I get sunlight in the morning I'll trace it back and clean it off and see if I can get a definite color. Here's one last pic. The green highlighted area of the wire goes back to the alternator, the blue is where the link went and the grey is where it changes To a red wire that goes on the driver's side under the brake cylinder. That's where I'll trace it back to see where it goes as soon as I have daylight. Thanks for your super fast responses. I'll get back with more info in a few hours in the morning! Rest well and thanks again.
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Monday, June 22nd, 2020 AT 11:00 PM
Tiny
IVARCJ
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Good morning. After looking at it further and tracing wires I can confirm it is number 2 from the pic you provided as it goes to the starter but is also spliced back and goes to the charging post at the upper left of the pic you provided. Ultimately and predominantly it is a red wire as well. The only part that is brown with a red stripe is from the alt to the fusible link, after that it is all red wire.
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Tuesday, June 23rd, 2020 AT 11:04 AM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 110,068 POSTS
Okay, that is constant power to the alternator right from the starter. Make sure nothing near the alternator has shorted. Also, I recommend removing the alternator and having it bench tested. You said you were getting 12.9v with the engine running. If that was with all things off (fan, lights, wipers, and so on), that is actually a bit low. I would expect it to have been near 14v with it running. I think something may have shorted in the alternator itself.

Let me know what you find or if you have other questions.

Joe
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Tuesday, June 23rd, 2020 AT 7:31 PM
Tiny
IVARCJ
  • MEMBER
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Good evening Joe,

So I ended up properly soldering, taping, heat shrinking and taping a 6" piece of matching 4g battery cable in place of where the fusible link "would go" then returned the wire loom after going around the block a few times and then re- checking if there was any heat coming from that area and everything is fine for now. I'm not getting any heat from the wire or warning lights inside the Jeep. I suspect I was using to thin a wire before( when I temporarily had a jumper to test) and that's why it was getting hot. I do have another factory harness piece ordered but it won't arrive for about a week so I decided to try soldering the battery cable piece directly and it's working fine. Upon retesting I am getting proper voltages and amperage's both at idle and under load with radio and a/c and lights running. Thank you so much for taking the time to walk me through things and provide schematics and just being another "brain" helping analyze my issue. Is there anything I can do to help you or this site in return for your services? I'm enclosing a pic of the 6" piece I soldered in line for now until I get my harness in. Thanks again for all your help sir.
Sincerely,
Chris Herrera
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Thursday, June 25th, 2020 AT 6:16 PM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 110,068 POSTS
Wow, that looks like a factory part! Excellent work. I would let you work on my own car.

Listen, you own us nothing. I'm just glad you got it fixed. Please feel free to come back anytime. In all honesty, I have a feeling your post is going to help others, so in a way, you already helped us. I have a 2013 Durango and it has the same design. Chances are I'll be calling on you for help.

Take care of yourself and come back anytime.

Joe
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Thursday, June 25th, 2020 AT 9:06 PM

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