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Alternator wiring diagram?

Tiny
PACKERS27
  • MEMBER
  • 2000 FORD F-150
  • 5.4L
  • V8
  • 4WD
  • AUTOMATIC
  • 200,000 MILES
I got in my truck and the car charger for my phone was beeping, indicating the voltage was low. At that time it was 11.4 volts. I drove about five miles and the battery gauge dropped to zero. Wipers were barely moving. I started noticing resistance while driving. All of a sudden all of the gauges dropped to zero and the truck shut off. I looked under the under and the hot wire and rubber boot burned completely off the alternator. Truck is completely out. The nut on alternator is still tight. I checked voltage to battery and it is showing 10 volts. I need some serious help here.
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Saturday, June 9th, 2018 AT 2:43 PM

24 Replies

Tiny
CARADIODOC
  • MECHANIC
  • 33,741 POSTS
It sounds like the wiring is bad but to be sure here is a guide to help check it with the alternator wiring diagrams below.

https://www.2carpros.com/articles/how-to-check-wiring

Check out the diagrams (Below). Please let us know what happens.
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Saturday, June 9th, 2018 AT 7:12 PM
Tiny
PACKERS27
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The nut was still on the stud but was so bad that it twisted off the stud when I tried to loosen it. Is there a piece I can buy that I can use as a stud or do I have to get one from a junk yard?

To add to this, it was not too long ago that I checked my connections at the battery and alternator as a general check up. Now here I am. The alternator stud looks kind of white like it is corrosion. Can an alternator connection get as corroded as you see some battery terminals do?
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Saturday, June 9th, 2018 AT 8:11 PM
Tiny
PACKERS27
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  • 187 POSTS
Stud twisted off with the nut I meant to say. Was this due to the heat or corrosion?
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Saturday, June 9th, 2018 AT 8:12 PM
Tiny
CARADIODOC
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The heat is what does the damage, but that is caused by the current flowing through a very light film of corrosion. This can happen on any brand of vehicle, but fortunately it is not real common. Chances of this happening again to you is very remote.
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Saturday, June 9th, 2018 AT 10:30 PM
Tiny
CARADIODOC
  • MECHANIC
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Any chance you are in Wisconsin?
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Saturday, June 9th, 2018 AT 10:31 PM
Tiny
PACKERS27
  • MEMBER
  • 187 POSTS
No, I am in Tennessee but love the Packers.

What other things causes these wires to burn up? Someone said something about grounds. Is that likely? If so, which ones should I be looking at and where are they on my truck?
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Saturday, June 9th, 2018 AT 10:45 PM
Tiny
CARADIODOC
  • MECHANIC
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Dandy. I am ninety miles straight west of Green Bay. I do have a cousin who plays violin for the Nashville Symphony Orchestra. She has more musical talent in her little finger than I have in my entire life!

Grounds can cause problems, but not in this case. You cannot get a better ground connection than the bracket the generator is bolted to. If you could do something to degrade that electrical connection, the symptom would be very low output current, and that bad connection is where the heat would build up. We never discuss grounds for generators or starters because for those to cause a problem, bolts would have to be loose or missing, and that would cause some pretty serious symptoms. By "serious", I mean obvious.
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Sunday, June 10th, 2018 AT 12:58 AM
Tiny
PACKERS27
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  • 187 POSTS
Very very interesting!

Just a few more questions and I will be on my way. I like to learn all of this you are telling me.

Okay, I do not know what amp size generator but I do not have any kind of mods or customization's. What amp size do you recommend if I were to buy one? As you stated, you do not see anything wrong with the current generator, right?

Okay, a better question, all of the stud was burned off. AutoZone does not sell that piece that bolts on the back of it I will have to buy a new alternator is what they tell me. Is there something I can buy to serve the same purpose or do I need a new generator now?
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Sunday, June 10th, 2018 AT 2:39 PM
Tiny
CARADIODOC
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I never looked closely at the style you have. Pictures show a tall stud sticking up more than an inch, I am guessing to clear something else on the engine. What I would do is remove the generator from the engine, take it to the re-builder, and let them look at it and offer suggestions. That stud might be connected to something internal that has also been burned away.
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Sunday, June 10th, 2018 AT 7:46 PM
Tiny
PACKERS27
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  • 187 POSTS
Ha ha. Gotcha. I have been doing some street walking to promote my pest control business and I have left my truck running for twenty minutes at a time due to excessive heat index. A couple of days before this, I washed my truck at the car wash. Since then, I have a P0308 which means cylinder eight is misfiring. These trucks are not meant to be washed because I hear they are bad about water getting into the plugs. Anyway, would either of these problems play a role in what happened to the generator wire at the alt terminal fast corrosion. I would not think so, but want to make sure.

So you think since the burn was at the location of the stud, it was probably corrosion and you feel confident that hooking it back up after I shine up all my connections would work?
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Sunday, June 10th, 2018 AT 8:59 PM
Tiny
CARADIODOC
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The main issue is a real lot of current through a relatively small conductor. When a connection burns up, we look for a reason it happened there and not any of the other just-as-vulnerable places along that circuit. Why did one of them overheat and another one didn't?
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Sunday, June 10th, 2018 AT 9:42 PM
Tiny
PACKERS27
  • MEMBER
  • 187 POSTS
It burned right behind the terminal. Only thing left was the terminal on the stud. It was burned too because it all twisted off when I tried to loosen the nut. It was white-ish color. Not sure if that color was from being burned or corrosion.
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Sunday, June 10th, 2018 AT 10:20 PM
Tiny
PACKERS27
  • MEMBER
  • 187 POSTS
With that alternator showing 15.10, does that not seem high to you? I suspect that there was a bad connection, but could that alternator be a culprit?
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Monday, June 11th, 2018 AT 9:16 AM
Tiny
PACKERS27
  • MEMBER
  • 187 POSTS
Well, I could not find a stud part to go on my alternator so I bought a new one. Since the 95 amp and 130 amp are different size alternators, the 130 amp is the one that fits on my bracket. I made sure my connection was good and I have been driving for two days with no problem. My phone truck charger gives a digital read out of 13.7 - 14.2 volts. Assuming that is okay.
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Tuesday, June 12th, 2018 AT 6:26 PM
Tiny
CARADIODOC
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The perfect range for charging voltage is 13.75 to 14.75 volts. 15.10 is high but not excessive. What you need to do is measure the voltage at the battery once the system is repaired. The voltage regulator can only do so much by itself. It needs the battery to help it, but that is not in the circuit when the output wire is burned open. It is not unheard of for a generator to develop 18 volts or more when there is no load on it. It depends on how that system works.
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Tuesday, June 12th, 2018 AT 7:04 PM
Tiny
CARADIODOC
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Just saw your last post. Happy to see you solved it. Please come back and see us again.
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Tuesday, June 12th, 2018 AT 7:07 PM
Tiny
WDCRAWELL
  • MEMBER
  • 1 POST
  • 1988 FORD F-150
Could you please tell me the wiring diagram for the alternator
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Tuesday, December 22nd, 2020 AT 9:23 AM (Merged)
Tiny
SATURNTECH9
  • MECHANIC
  • 30,870 POSTS
Here is a guide to elp to test the wiring with the alternator wiring diagrams below.

https://www.2carpros.com/articles/how-to-check-wiring

Check out the diagrams (Below). Please let us know if you need anything else to get the problem fixed.

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Tuesday, December 22nd, 2020 AT 9:23 AM (Merged)
Tiny
SPINEL_GORE
  • MEMBER
  • 1 POST
  • 1988 FORD F-150
Electrical problem
1988 Ford F150 V8 Four Wheel Drive Manual

i need to know where a wire goes on my alternator so I need a pic of it
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Tuesday, December 22nd, 2020 AT 9:23 AM (Merged)
Tiny
BLUELIGHTNIN6
  • MECHANIC
  • 16,542 POSTS


https://www.2carpros.com/forum/automotive_pictures/261618_0900c152801cd3b9_1.jpg

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Tuesday, December 22nd, 2020 AT 9:23 AM (Merged)

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