Why did this ground wire melt ?
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Why did this ground wire melt ?
Got the charging system working, it's got a solid state voltage regulator now. It checks out good with the multi meter, and now you can hear the alternator working.
The problem is, the black ground wire that comes from the wiring harness, and attaches to the radiator support, where the voltage regulator is screwed on, melted.
What is the purpose of this wire? Where does it come from? What would cause it to melt? How should I fix this problem?
Thanks for your answers, and advice.
The problem is, the black ground wire that comes from the wiring harness, and attaches to the radiator support, where the voltage regulator is screwed on, melted.
What is the purpose of this wire? Where does it come from? What would cause it to melt? How should I fix this problem?
Thanks for your answers, and advice.
Fleet Mechanic
Joined: May 2001
Posts: 1,396
Likes: 4
From: Cupertino
It was not a ground or it would not have melted.
I don't know what the application is, but the schematics for 1967 show a common ground between the alternator and regulator. The regulator takes its ground through the case and the alternator has a G lug that goes to the block. Make sure the alternator case is grounded.
Since the wire is burnt off, check with your voltmeter to see what is on it. If you see battery voltage or something like it, don't attempt to ground it.
You will see a tubular radio supression capacitor coming from the regulator to ground. There is a one-in-a-million chance that the capacitor has shorted and that may be the black wire you are talking about. Disconnect and check the capacitor on the ohms scale- infinity is the right answer.
Capacitors almost always fail open-circuit but one never can tell.
I don't know what the application is, but the schematics for 1967 show a common ground between the alternator and regulator. The regulator takes its ground through the case and the alternator has a G lug that goes to the block. Make sure the alternator case is grounded.
Since the wire is burnt off, check with your voltmeter to see what is on it. If you see battery voltage or something like it, don't attempt to ground it.
You will see a tubular radio supression capacitor coming from the regulator to ground. There is a one-in-a-million chance that the capacitor has shorted and that may be the black wire you are talking about. Disconnect and check the capacitor on the ohms scale- infinity is the right answer.
Capacitors almost always fail open-circuit but one never can tell.
Cranky Old Guy
Joined: Mar 2008
Posts: 3,562
Likes: 6
From: Raphine, Virginia
Ground wires will melt. They are just the other half of a complete circuit. Replace your neg batt cable with a small gauge wire and see what happens. Just arguing the point that it is possible.
Fleet Mechanic
Joined: May 2001
Posts: 1,396
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From: Cupertino
The alternator takes a heavy ground through the metal case through the mounting bolt to the engine. There should be a heavy #6 ground strap from the engine to the chassis frame. The ground from the alternator case to the block and the ground to the alternator is redundant.
No ground or any other wire should ever melt.
No ground or any other wire should ever melt.
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Well, now that the wire loom is unwrapped, it should be easier to figure out the problem. The melted black wire that is grounded to the chassis has been connected to the alternator at the post labeled STA. I think I did this, when I was trying to figure out why the alternator was not putting out power. Pretty sure the wire was supposed to be connected to the post labeled GRD.
The BAT, and the FLD connections are no brainers, because the end of the wire loom is made to only connect those one way.
If the wire is replaced, is that the correct way to ground the alternator? From the GRD post to the chassis?
Should there be a wire connected to the post labeled STA?
The BAT, and the FLD connections are no brainers, because the end of the wire loom is made to only connect those one way.
If the wire is replaced, is that the correct way to ground the alternator? From the GRD post to the chassis?
Should there be a wire connected to the post labeled STA?
Fleet Mechanic
Joined: May 2001
Posts: 1,396
Likes: 4
From: Cupertino
You have not given us the application but referring to the 1967 manual fig. 5 section 13-20, the stator hangs open on a vehicle with an ammeter and a transistor regulator.
Do not ground the stator.
The ground wire on the alternator goes to a good ground wherever you can find one. Stock is a bolt into the block. The manual shows one from the regulator to the alternator but as I posted it is redundant.
Check to see that the ground strap from the block to the cab is intact. Make sure that you have scuffed up the mounting bolts through the regulator where it mounts. That is where it takes its ground. Tighten radiator supports if that is where it mounts.
The block is grounded to the frame through the motor mounts, through the transmission to the transmission mounts, through the cab strap. There are grounds all over the place. It is hard to lift a ground on this old iron. I will bet that 15% of the trucks of this era are running around without a cab strap.
You may have fried diodes in the alternator by grounding what you did. Check for 14.5 volts at the battery at fast idle.
Do not ground the stator.
The ground wire on the alternator goes to a good ground wherever you can find one. Stock is a bolt into the block. The manual shows one from the regulator to the alternator but as I posted it is redundant.
Check to see that the ground strap from the block to the cab is intact. Make sure that you have scuffed up the mounting bolts through the regulator where it mounts. That is where it takes its ground. Tighten radiator supports if that is where it mounts.
The block is grounded to the frame through the motor mounts, through the transmission to the transmission mounts, through the cab strap. There are grounds all over the place. It is hard to lift a ground on this old iron. I will bet that 15% of the trucks of this era are running around without a cab strap.
You may have fried diodes in the alternator by grounding what you did. Check for 14.5 volts at the battery at fast idle.
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Thanks for the information.
The truck is a 69 F100, with a 360.
I will get everything hooked back up correctly, and hopefully all is good.
Is it ok, or normal to have no wire going to the post on the alternator labeled STA ?
The truck is a 69 F100, with a 360.
I will get everything hooked back up correctly, and hopefully all is good.
Is it ok, or normal to have no wire going to the post on the alternator labeled STA ?
Hotshot
Joined: Oct 2002
Posts: 18,488
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From: The Big, Oregon
The block is grounded to the frame through the motor mounts, through the transmission to the transmission mounts, through the cab strap. There are grounds all over the place. It is hard to lift a ground on this old iron. I will bet that 15% of the trucks of this era are running around without a cab strap.
You may have fried diodes in the alternator by grounding what you did. Check for 14.5 volts at the battery at fast idle.
You may have fried diodes in the alternator by grounding what you did. Check for 14.5 volts at the battery at fast idle.
The main vehicle ground is to the engine block, with a strap to the cab at the rear and to the frame at the front.
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