3G alternator new or used?

[Gary Lewis]

BTW, not to be pedantic, I noticed your tutorial says 8.125" mounting, but it is 8.25" as shown in Ryan's pic.

Thanks, Jim. It is fixed.

[86-350-460-dually]

Thanks, Jim. It is fixed.

It appears as though I have hit a snag. I had a plan.... Lol

I was going to get behind the ammeter to test if it's drawing battery power or not. I've got everything removed, except the cluster. I have since learned that there are not wires that plug into the ammeter, it's a circuit board. The idea was to test it and see if it's drawing power, then cut the wire, cap it and all is well.

Now, with the circuit board, I'm not sure what to do anymore to find that wire to the ammeter. Is it something I can find in the engine bay somewhere?

[Gary Lewis]

It appears as though I have hit a snag. I had a plan.... Lol

I was going to get behind the ammeter to test if it's drawing battery power or not. I've got everything removed, except the cluster. I have since learned that there are not wires that plug into the ammeter, it's a circuit board. The idea was to test it and see if it's drawing power, then cut the wire, cap it and all is well.

Now, with the circuit board, I'm not sure what to do anymore to find that wire to the ammeter. Is it something I can find in the engine bay somewhere?

Adam - You are right, you can't really figure it out inside the cab. The shunt we've been talking about shows on Page 17 here (Electrical/1985 EVTM/Charge & Power Distribution (Gas)), right below the ammeter in the illustration.

Note that one end of the shunt hooks to the starter relay/solenoid, and the shunt is a black/orange wire. From the solenoid end of the shunt there is a red/orange wire going to the ammeter, and from the other end of the shunt there's a yellow/light green wire going to the other side of the ammeter.

The voltage that is created across the shunt when current flows in it is extremely small. Way, way less than a volt. So small you almost can't measure it with a DVM. And, the ammeter is so sensitive that if you put your DVM on the resistance setting and try to measure the meter you will probably damage it.

In reality, when you replace the alternator you need to disconnect the wires going to the ammeter and replace the shunt with a piece of larger wire.

[Steve83]

...I don't know what I have is stock or not.

It's certainly not.

There is no external fan on the passenger fender.

Your pic clearly shows an external fan on the alt (which is characteristic of the 1G & 2G). The ~5x5" steel box on the fender would be the external voltage regulator, as this pic shows:

https://supermotors.net/getfile/859765/thumbnail/1ghd.jpg

That's pretty scary, and likely a BIG part of your charging problems. The alt body should be TIGHT between the bracket & bolt head (with sliding sleeve, which your bracket still has); and the bracket should be TIGHT to the head or block; and ALL those mating surfaces should be clean & shiny metal (with electrical grease applied - NOT dielectric, or chassis, or thermal, or battery snot, or anti-sieze, or...).

Try to get a well-lit focused pic showing all the wire connections on the back of the alt. My impression is that your pic shows a 1G, but there's not actually enough visible to be sure.

...I'm not understanding is the janky stud (what do you mean by that?)

Your alt is only marginally-tight to the bracket due to the nut & washer behind it (visible in the 2nd pic). But that same nut & washer are also PREVENTING the bracket from being truly tight against the head at that location. It should be a simple LONG bolt, and the alt body should take up all the gap between the back of the bracket & the sliding sleeve in the front of the bracket. A spacer is OK, but not ideal.

And can you explain what you mean by the fuse box connector thingy? I'm not quite understanding that.

Most circuits need protection, and the original protection for the charging circuit was a fusible link wire (a normal wire inside special insulation sized to burn out under specific conditions). But Ford changed the circuit design on later 3Gs & all subsequent alt.s to a MEGA fuse, which is easier for most people to understand & replace. So it's a good idea to swap to that when you swap to a 3G, and it's cheap & easy if you get a used 3G since you can get that harness section with fuses at the same JY. This one also has a fuse on the small Y wire:

https://supermotors.net/getfile/876977/thumbnail/3gharness.jpg

I assume that's the D&G meter in the dash? No, mine does not work one bit.

D(rain) & C(harge). That it doesn't work proves nothing - they didn't really work new, which is another reason to get rid of that circuit, and switch to a true voltmeter (like all modern vehicles).

...the big coil of wire up inside the dashboard...

...a resistance wire glowing red hot up inside the dash...

The shunt isn't a coil; it's not all in the dash; it's not really resistor wire; and it would never glow. It's a normal heavy Copper wire in the harness sections from the starter relay area to the ignition switch area. It might be wrapped or folded inside the harness to get the designed length, but it's not really "coiled". It has resistance only because it's old Copper - they didn't have the infrastructure back then to process Cu as purely as we have now. But it was never designed to have a specific resistance; they just used its natural resistance for the gauge. If you try to run a HO alt through it, the connectors would burn out long before the wire got hot enough to glow, or even melt its insulation. But those connections COULD still start a fire.

...inside the cab.

...there is a red/orange wire going to the ammeter, and from the other end of the shunt there's a yellow/light green wire going to the other side of the ammeter.

That's actually all he needs to find it right there on the back of the cluster, inside the cab.

So small you almost can't measure it with a DVM. And, the ammeter is so sensitive that if you put your DVM on the resistance setting and try to measure the meter you will probably damage it.

Any modern DMM (even a $10 one) is vastly more-sensitive & -accurate than that old gauge. And the gauge isn't delicate at all - any DMM has ~10,000x more resistance than that old gauge, so the meter won't hurt the gauge.

...replace the shunt with a piece of larger wire.

The shunt is large enough for what it will be doing after the alternator output is run directly to the starter relay (battery side), so it's not worth the effort or risk to pull a wire out of the harness. Just disconnect & tag the gauge wires, in case you find some other use for them later (like LEDs...).

[ArdWrknTrk]

...I don't know what I have is stock or not.

It's certainly not.

There is no external fan on the passenger fender.

Your pic clearly shows an external fan on the alt (which is characteristic of the 1G & 2G). The ~5x5" steel box on the fender would be the external voltage regulator, as this pic shows:

https://supermotors.net/getfile/859765/thumbnail/1ghd.jpg

That's pretty scary, and likely a BIG part of your charging problems. The alt body should be TIGHT between the bracket & bolt head (with sliding sleeve, which your bracket still has); and the bracket should be TIGHT to the head or block; and ALL those mating surfaces should be clean & shiny metal (with electrical grease applied - NOT dielectric, or chassis, or thermal, or battery snot, or anti-sieze, or...).

Try to get a well-lit focused pic showing all the wire connections on the back of the alt. My impression is that your pic shows a 1G, but there's not actually enough visible to be sure.

...I'm not understanding is the janky stud (what do you mean by that?)

Your alt is only marginally-tight to the bracket due to the nut & washer behind it (visible in the 2nd pic). But that same nut & washer are also PREVENTING the bracket from being truly tight against the head at that location. It should be a simple LONG bolt, and the alt body should take up all the gap between the back of the bracket & the sliding sleeve in the front of the bracket. A spacer is OK, but not ideal.

And can you explain what you mean by the fuse box connector thingy? I'm not quite understanding that.

Most circuits need protection, and the original protection for the charging circuit was a fusible link wire (a normal wire inside special insulation sized to burn out under specific conditions). But Ford changed the circuit design on later 3Gs & all subsequent alt.s to a MEGA fuse, which is easier for most people to understand & replace. So it's a good idea to swap to that when you swap to a 3G, and it's cheap & easy if you get a used 3G since you can get that harness section with fuses at the same JY. This one also has a fuse on the small Y wire:

https://supermotors.net/getfile/876977/thumbnail/3gharness.jpg

I assume that's the D&G meter in the dash? No, mine does not work one bit.

D(rain) & C(harge). That it doesn't work proves nothing - they didn't really work new, which is another reason to get rid of that circuit, and switch to a true voltmeter (like all modern vehicles).

...the big coil of wire up inside the dashboard...

...a resistance wire glowing red hot up inside the dash...

The shunt isn't a coil; it's not all in the dash; it's not really resistor wire; and it would never glow. It's a normal heavy Copper wire in the harness sections from the starter relay area to the ignition switch area. It might be wrapped or folded inside the harness to get the designed length, but it's not really "coiled". It has resistance only because it's old Copper - they didn't have the infrastructure back then to process Cu as purely as we have now. But it was never designed to have a specific resistance; they just used its natural resistance for the gauge. If you try to run a HO alt through it, the connectors would burn out long before the wire got hot enough to glow, or even melt its insulation. But those connections COULD still start a fire.

...inside the cab.

...there is a red/orange wire going to the ammeter, and from the other end of the shunt there's a yellow/light green wire going to the other side of the ammeter.

That's actually all he needs to find it right there on the back of the cluster, inside the cab.

So small you almost can't measure it with a DVM. And, the ammeter is so sensitive that if you put your DVM on the resistance setting and try to measure the meter you will probably damage it.

Any modern DMM (even a $10 one) is vastly more-sensitive & -accurate than that old gauge. And the gauge isn't delicate at all - any DMM has ~10,000x more resistance than that old gauge, so the meter won't hurt the gauge.

...replace the shunt with a piece of larger wire.

The shunt is large enough for what it will be doing after the alternator output is run directly to the starter relay (battery side), so it's not worth the effort or risk to pull a wire out of the harness. Just disconnect & tag the gauge wires, in case you find some other use for them later (like LEDs...).

I stand corrected Steve.

Should have said bundle instead of coil.

While I have to think 'resistance' is probably my phone's autocorrect for *resistive.

The "ammeter" is a good example of the time honored voltage drop test, often suggested for finding something like an internally corroded ground or starter cable.

Anyway, good observations and succinct answers.

Hopefully this clears things up and helps Adam get his truck going

 

[Gary Lewis]

...I don't know what I have is stock or not.

It's certainly not.

There is no external fan on the passenger fender.

Your pic clearly shows an external fan on the alt (which is characteristic of the 1G & 2G). The ~5x5" steel box on the fender would be the external voltage regulator, as this pic shows:

https://supermotors.net/getfile/859765/thumbnail/1ghd.jpg

That's pretty scary, and likely a BIG part of your charging problems. The alt body should be TIGHT between the bracket & bolt head (with sliding sleeve, which your bracket still has); and the bracket should be TIGHT to the head or block; and ALL those mating surfaces should be clean & shiny metal (with electrical grease applied - NOT dielectric, or chassis, or thermal, or battery snot, or anti-sieze, or...).

Try to get a well-lit focused pic showing all the wire connections on the back of the alt. My impression is that your pic shows a 1G, but there's not actually enough visible to be sure.

...I'm not understanding is the janky stud (what do you mean by that?)

Your alt is only marginally-tight to the bracket due to the nut & washer behind it (visible in the 2nd pic). But that same nut & washer are also PREVENTING the bracket from being truly tight against the head at that location. It should be a simple LONG bolt, and the alt body should take up all the gap between the back of the bracket & the sliding sleeve in the front of the bracket. A spacer is OK, but not ideal.

And can you explain what you mean by the fuse box connector thingy? I'm not quite understanding that.

Most circuits need protection, and the original protection for the charging circuit was a fusible link wire (a normal wire inside special insulation sized to burn out under specific conditions). But Ford changed the circuit design on later 3Gs & all subsequent alt.s to a MEGA fuse, which is easier for most people to understand & replace. So it's a good idea to swap to that when you swap to a 3G, and it's cheap & easy if you get a used 3G since you can get that harness section with fuses at the same JY. This one also has a fuse on the small Y wire:

https://supermotors.net/getfile/876977/thumbnail/3gharness.jpg

I assume that's the D&G meter in the dash? No, mine does not work one bit.

D(rain) & C(harge). That it doesn't work proves nothing - they didn't really work new, which is another reason to get rid of that circuit, and switch to a true voltmeter (like all modern vehicles).

...the big coil of wire up inside the dashboard...

...a resistance wire glowing red hot up inside the dash...

The shunt isn't a coil; it's not all in the dash; it's not really resistor wire; and it would never glow. It's a normal heavy Copper wire in the harness sections from the starter relay area to the ignition switch area. It might be wrapped or folded inside the harness to get the designed length, but it's not really "coiled". It has resistance only because it's old Copper - they didn't have the infrastructure back then to process Cu as purely as we have now. But it was never designed to have a specific resistance; they just used its natural resistance for the gauge. If you try to run a HO alt through it, the connectors would burn out long before the wire got hot enough to glow, or even melt its insulation. But those connections COULD still start a fire.

...inside the cab.

...there is a red/orange wire going to the ammeter, and from the other end of the shunt there's a yellow/light green wire going to the other side of the ammeter.

That's actually all he needs to find it right there on the back of the cluster, inside the cab.

So small you almost can't measure it with a DVM. And, the ammeter is so sensitive that if you put your DVM on the resistance setting and try to measure the meter you will probably damage it.

Any modern DMM (even a $10 one) is vastly more-sensitive & -accurate than that old gauge. And the gauge isn't delicate at all - any DMM has ~10,000x more resistance than that old gauge, so the meter won't hurt the gauge.

...replace the shunt with a piece of larger wire.

The shunt is large enough for what it will be doing after the alternator output is run directly to the starter relay (battery side), so it's not worth the effort or risk to pull a wire out of the harness. Just disconnect & tag the gauge wires, in case you find some other use for them later (like LEDs...).

Steve - I pulled an ammeter off the shelf and did some testing.

• Full scale in the "C" direction takes only .170 volts. But, at that point it there is 1.0 amp running through the ammeter.

• Full scale in the "D" direction takes only .150 volts. And at that point there's .88 amp running through the ammeter.

So, even a cheap DVM can measure the voltage when the alternator is kicking out something like its full capability. But, it takes about .02v to start seeing any movement on the ammeter, so that could be missed.

And, I agree with you on the shunt being adequate to handle the normal load in the cab and, therefore, doesn't need to be replaced if the alternator's output is moved to the battery side of the solenoid. And especially if lights are replaced with LED's. But, I wouldn't want to start adding a lot of current hogs, like large audio amps, to the shunt's load. Anything big like that should have its own power source from the battery rather than come through the fuse box.

But, for grins I used the E=IR equation to calculate the resistance of the shunt. Assuming that it was designed to handle the 70 amp alternators that could come in these trucks, the shunt would have to be .002285 ohms to create .16 volts across it, which is the average of the .15 and .17 that I measured.

As it turns out, #14 wire has 2.525 ohms per 1000', or .0025 ohms per foot. So, that would be about right for the shunt. But, the tables say you should not run more than 32 amps through #14 wire, probably for fear that the insulation will melt or the wire will become brittle with the heat. Perhaps shunts are made of special wire and/or have special insulation like fuse links do?

Wondering about the heat I used the equation that Watts = IxIxR and found that the heat produced in the shunt at 70 amps would be 11.2 watts. It isn't likely that the wire would get very hot with that much heat. But, I don't have an easy way to test that theory so don't know for sure.

Last, the use of the wires to the ammeter is to run a voltmeter. That's my plan anyway. Ground one and put switched battery voltage to the other. I have already had Rocketman convert the ammeter to a voltmeter.

 

[Steve83]

I wouldn't want to start adding a lot of current hogs, like large audio amps, to the shunt's load. Anything big like that should have its own power source from the battery rather than come through the fuse box.

That could be said of any wire in any vehicle of any year. My statement wasn't intended to be all-inclusive. I was referring to a vehicle whose only modification is the 3G swap. Naturally, any combination of mods has to be specifically considered for the interactions between those specific mods.

But the shunt is designed to be a main wire in the harness, carrying the alternator's full output. So it can handle quite a bit of current (assuming no damage & normal maintenance).

But, the tables say you should not run more than 32 amps through #14 wire, probably for fear that the insulation will melt or the wire will become brittle with the heat.

There are MANY tables; each one with its author's specific considerations, resulting in MANY variations in current capacity. Those written for aircraft are different from boats, which are different from trucks...

https://supermotors.net/getfile/1007183/thumbnail/wiregaugecurrentlengtht.gif

In some cases, the primary concern is insulation viscosity at temperature; in other cases, it's voltage drop.

Perhaps shunts are made of special wire and/or have special insulation like fuse links do?

Not this one. It's just normal wire USED as a shunt; not specifically manufactured as a shunt.

...11.2 watts. It isn't likely that the wire would get very hot with that much heat. But, I don't have an easy way to test that theory...

Look at a 194 bulb (instrument cluster backlighting):

https://supermotors.net/getfile/832986/thumbnail/bulbsfuseswire.jpg

So that whole ~20'-long 14ga wire is putting off about as much heat (NOT TEMPERATURE) as one of those tiny bulbs.

Last, the use of the wires to the ammeter is to run a voltmeter. ... Ground one and put switched battery voltage to the other.

That would be redundant since the instrument cluster already has a switched 12V circuit, and a ground. Just use the wires that are already there (and already properly fused/connected), and save the ammeter wires for something else.

[Vic Roma]

I wouldn't want to start adding a lot of current hogs, like large audio amps, to the shunt's load. Anything big like that should have its own power source from the battery rather than come through the fuse box.

That could be said of any wire in any vehicle of any year. My statement wasn't intended to be all-inclusive. I was referring to a vehicle whose only modification is the 3G swap. Naturally, any combination of mods has to be specifically considered for the interactions between those specific mods.

But the shunt is designed to be a main wire in the harness, carrying the alternator's full output. So it can handle quite a bit of current (assuming no damage & normal maintenance).

But, the tables say you should not run more than 32 amps through #14 wire, probably for fear that the insulation will melt or the wire will become brittle with the heat.

There are MANY tables; each one with its author's specific considerations, resulting in MANY variations in current capacity. Those written for aircraft are different from boats, which are different from trucks...

https://supermotors.net/getfile/1007183/thumbnail/wiregaugecurrentlengtht.gif

In some cases, the primary concern is insulation viscosity at temperature; in other cases, it's voltage drop.

Perhaps shunts are made of special wire and/or have special insulation like fuse links do?

Not this one. It's just normal wire USED as a shunt; not specifically manufactured as a shunt.

...11.2 watts. It isn't likely that the wire would get very hot with that much heat. But, I don't have an easy way to test that theory...

Look at a 194 bulb (instrument cluster backlighting):

https://supermotors.net/getfile/832986/thumbnail/bulbsfuseswire.jpg

So that whole ~20'-long 14ga wire is putting off about as much heat (NOT TEMPERATURE) as one of those tiny bulbs.

Last, the use of the wires to the ammeter is to run a voltmeter. ... Ground one and put switched battery voltage to the other.

That would be redundant since the instrument cluster already has a switched 12V circuit, and a ground. Just use the wires that are already there (and already properly fused/connected), and save the ammeter wires for something else.

Today my bone stock truck fell victim to the 2G fire. I had to douse the flames with a water spray bottle (on an electrical fire!) and in doing so the 16GA fusable link solenoid wire on the RH fender blew out.

Here’s a photo of the wire for your entertainment.

I read on this site the following on alternator fires:

“There has been a recent investigation of alternators manufactured by Ford. This article provides facts and information from the Ford investigation.

In one instance, the driver smelled smoke and discovered a fire underneath the hood of his Ford Aerostar. After the Fire Company extinguished the fire, investigators determined that the wiring at the plug connector melted and caused high resistance overload. According to the National Highway Traffic Safety Administration (NHTSA) there are 75 fires allegedly caused by the Ford Alternator. Ford uses a plug connector and not the conventional attachment. Investigators think that this plug connector develops high resistance over time and becomes even more dangerous when it is removed and reconnected. Currently Ford and the NHTSA are conducting further investigations into Ford alternators.”

I also read the comments about swapping it out to avoid potential fires (never expecting it on my truck), and so here’s my stupid question of the day:

Would Ford (dealership) do anything about this, or is it on me to fix?

[Gary Lewis]

Today my bone stock truck fell victim to the 2G fire. I had to douse the flames with a water spray bottle (on an electrical fire!) and in doing so the 16GA fusable link solenoid wire on the RH fender blew out.

Here’s a photo of the wire for your entertainment.

I read on this site the following on alternator fires:

“There has been a recent investigation of alternators manufactured by Ford. This article provides facts and information from the Ford investigation.

In one instance, the driver smelled smoke and discovered a fire underneath the hood of his Ford Aerostar. After the Fire Company extinguished the fire, investigators determined that the wiring at the plug connector melted and caused high resistance overload. According to the National Highway Traffic Safety Administration (NHTSA) there are 75 fires allegedly caused by the Ford Alternator. Ford uses a plug connector and not the conventional attachment. Investigators think that this plug connector develops high resistance over time and becomes even more dangerous when it is removed and reconnected. Currently Ford and the NHTSA are conducting further investigations into Ford alternators.”

I also read the comments about swapping it out to avoid potential fires (never expecting it on my truck), and so here’s my stupid question of the day:

Would Ford (dealership) do anything about this, or is it on me to fix?

The only stupid question is the one you didn't ask, and you asked this one so it isn't stupid. However, I think the answer would be accompanied by . But, if it was me I'd ask.

Just FYI, we have a TSB on the 2G problem on the site here: http://www.garysgaragemahal.com/96-21-04-2g-alternator-repair.html

Anyway, sorry about your truck. Glad you got the fire out quickly.

[ArdWrknTrk]

Today my bone stock truck fell victim to the 2G fire. I had to douse the flames with a water spray bottle (on an electrical fire!) and in doing so the 16GA fusable link solenoid wire on the RH fender blew out.

Here’s a photo of the wire for your entertainment.

I read on this site the following on alternator fires:

“There has been a recent investigation of alternators manufactured by Ford. This article provides facts and information from the Ford investigation.

In one instance, the driver smelled smoke and discovered a fire underneath the hood of his Ford Aerostar. After the Fire Company extinguished the fire, investigators determined that the wiring at the plug connector melted and caused high resistance overload. According to the National Highway Traffic Safety Administration (NHTSA) there are 75 fires allegedly caused by the Ford Alternator. Ford uses a plug connector and not the conventional attachment. Investigators think that this plug connector develops high resistance over time and becomes even more dangerous when it is removed and reconnected. Currently Ford and the NHTSA are conducting further investigations into Ford alternators.”

I also read the comments about swapping it out to avoid potential fires (never expecting it on my truck), and so here’s my stupid question of the day:

Would Ford (dealership) do anything about this, or is it on me to fix?

Really glad you didn't lose the truck Vic! 🙏

No, they're not going to do anything about a popped fuse link.

But what you can do is upgrade to the much safer 3G alternator, and use a HMEG with a fuse instead of relying on an undersized wire to protect your truck.