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Driving home for the first time at night I noticed my lights getting dim. I also noticed what I’m assuming is the alternator warning light coming on. I was just a mile or so from home so I got home quick. When I got home I noticed the attached pictures. Please help me diagnose. The wire connector was not connected to the alternator.

 

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*LongFella posted:

That red wire goes to the B+ on the alternator. Could/Can the alternator over produce and heat the wire like that??

The alternator sends power equal to what’s being drained from the battery through that wire, then back to the battery through the positive battery cable. Lots of times, that alternator wire is pretty skimpy for the current running through it. If you’ve got high output headlights, it could absolutely do that. 

Before you do anything check to see if that wire may have been pinched somewhere. Then start the engine and test to conform your Alt. is putting about approx. 13.8 volts at around 2,000 Rpms. The wire in the photo appears to be not heavy enough , you want a 10 gauge this runs from B+ on the Alt. to the starter 12v. lug where the battery cable is secured.

 

Last edited by Alan Merklin
Stan Galat posted:
*LongFella posted:

That red wire goes to the B+ on the alternator. Could/Can the alternator over produce and heat the wire like that??

The alternator sends power equal to what’s being drained from the battery through that wire, then back to the battery through the positive battery cable. Lots of times, that alternator wire is pretty skimpy for the current running through it. If you’ve got high output headlights, it could absolutely do that. 

Any suggestions on wire gauge I should replace it with? Or any other suggestions? I had all lights on including fog lights and wipers. It started to rain on me. Overall it wasn’t my best evening drive.

Sam:    The last line of your post says; “The wire connector was not connected to the alternator.”

Please explain.  What WAS that end of the wire doing?  I see a nut on the B+ stud and the wire has a ring tab which tells me the nut must be removed before the wire is removed, so what happened?

If the nut got loose on the B+ Stud and the wire fell off, it could easily flop against metal and ground that end.  The other end of the wire goes directly to the battery bolt on the starter.  If that wire fell off at the alternator and shorted to something you get 400 amps through it and the charred remains that you posted.

Until we know more about what happened I would hesitate to suggest a stronger wire gauge.  A bigger wire certainly won’t hurt (and you must replace it anyway) but it might not be necessary.

It would also be prudent to attach an ohmeter to ground and the B+ stud before you connect a new B+ wire  to make sure it’s not shorted inside of the alternator.

Gordon Nichols posted:

Sam:    The last line of your post says; “The wire connector was not connected to the alternator.”

Please explain.  What WAS that end of the wire doing?  I see a nut on the B+ stud and the wire has a ring tab which tells me the nut must be removed before the wire is removed, so what happened?

If the nut got loose on the B+ Stud and the wire fell off, it could easily flop against metal and ground that end.  The other end of the wire goes directly to the battery bolt on the starter.  If that wire fell off at the alternator and shorted to something you get 400 amps through it and the charred remains that you posted.

Until we know more about what happened I would hesitate to suggest a stronger wire gauge.  A bigger wire certainly won’t hurt (and you must replace it anyway) but it might not be necessary.

It would also be prudent to attach an ohmeter to ground and the B+ stud before you connect a new B+ wire  to make sure it’s not shorted inside of the alternator.

Hey Gordon,

Thank you for the reply.

I recently had the car in the shop for a rear main seal replacement. I suspect the tech working on the car did not reattach the wire to the alternator. The two nuts are still in place. 

That or someone sabotaged me while at a car show. 

Ok, so sorry to hear of either scenario, but the alternator is probably just fine.

The B+ wire is about 3’ - 4’ long and goes from that stud on the alternator through a hole in the firewall (follow it along, you’ll see it) and on to the big stud on the starter solenoid on top of the starter.  If you or a mechanic remove it, you’ll know how long a new one must be and what size ring tabs go on each end.  It is probably a 10 ga wire but may be an 8 ga.  Either is OK, larger 8 ga is better.  Most decent garage shops can make one up right there or any auto electric place or even Best Buy Auto Install shop.  Automotive standards tell us it should be a red colored wire.

The important thing in this repair is to remember that that charred wire still has 12 volts and a LOT of current attached to it so be careful!  Don’t let the charred, raggedy end touch anything metal while removing it until you detach it from the starter end.  Very big sparks ensue.

I suspect it just wasn’t re-connected after the engine was re-installed (it happens).  It would look pretty obvious if someone removed it at a show.   They would need a wrench and a minute or two to remove it standing amongst other spectators.

So, other than your choco-chip wire, no other damage was probably done.

 Pop in a new one and you’re golden

Last edited by Gordon Nichols

Easy fix. Step 1: Disconnect negative battery cable from battery!

Step 2: Remove nasty charred wire and say a prayer for whoever/whatever blessed you that your car didn't burn to the ground! You can chant or put a pentagram with candles down, I don't care which.

Step 3: Replace wire, tying it and snugging the nuts down on both the starter and alternator.

Step 4: Reattach battery ground lead.

Step 5: Measure battery voltage, should be in the neighborhood of 12.1 to 12.2. Start car and measure battery voltage, should be in the neighborhood of 13.5 to 13.8.

Step 6: Crack open a barley-pop!

PS: my car came with a #10 from starter to dash. I added an 8 gauge that powers a heater, an audio amp, and a few other accessories like USB ports and Cig lighter.

My advice is replace it with a #8 or #6, as others have mentioned.

Last edited by DannyP

Thank you for all the replies. I replaced the wire myself with 8 gauge and did a better job at routing it. I already have a fire extinguisher mounted in the car. I spoke with the shop and they have been more than apologetic and are ready to help me in any way if any other issues arise with the electrical system. The tech even offered to come to my house to install the wire for me. 

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