Thermostat housing

[Esteban]

There should be a wire connected there. Almost all the current goes through the meter, except the starter.

Please note that an alternator supplies a fixed voltage but variable current output. With a partially depleted battery the alternator will try to give as much amperage as possible and you could max out the meter (30 amps or 50 amps depending on years)

But don’t worry. The meter can’t be damaged. Is just a magnetic flow that moves the needle. No coils with windings to be burn.

[timber]

There should be a wire connected there.

I thought that might be the case...
I will just take one of the wires off the right terminal and put it on the left.

Almost all the current goes through the meter, except the starter.

Makes sense...

Please note that an alternator supplies a fixed voltage but variable current output. With a partially depleted battery the alternator will try to give as much amperage as possible and you could max out the meter (30 amps or 50 amps depending on years)

I guess mine will be pegged at 50 a lot.

The hot wire that ran from the old alternator I took off was / is heavy. I think about 10 ga. I have not taken it out yet. I have only disconnected it at each end. I called the manufacturer for the new 120 amp alternator and they said it needs to be at least 6 ga, which I have now. They said the 6 ga wire needs to run from the alternator directly to the hot battery which I am in the process of doing. But the old 10 ga wire ran from the old alternator into the firewall to (I think) the ammeter and back out the firewall to the hot battery lead at the starter. "I think" because I have not deliberately traced it behind the firewall yet. It seems the wires on that single terminal on the ammeter are of heavier gauge.

That said; a few questions: Does the alternator wire need to run through the ammeter for the ammeter to work?
The new 6 ga wire is way too big to run to the ammeter; can I keep both the 6 ga and the original 10 ga wires connected and run in parallel (10 ga through the ammeter) to enable the ammeter to function?

I probably should start by reviewing how an ammeter is wired-which wires run to and from it....

I knew there would be unintended consequences of a heavier alternator......

It is very kind to help this old country boy from Georgia

Tom

Edit to add that the new alternator is Voltage Regulator Type: Internal (but not 1 wire capable)
Series: 17SI
I asked if it was 1 wire capable on the product Q and A on the O'Reilly website. In the specs it says its internally regulated. They initially said it was but then corrected themselves with this:

"Hello and thanks for the question. We have received an update from the manufacturer and they state this part number is not one wire capable. The exciter for this alternator is triggered by the ignition and thus needs to be connected to work which means more than one wire is connected to it. We apologize for the mix up."

[Esteban]

That said; a few questions: Does the alternator wire need to run through the ammeter for the ammeter to work?
The new 6 ga wire is way too big to run to the ammeter; can I keep both the 6 ga and the original 10 ga wires connected and run in parallel (10 ga through the ammeter) to enable the ammeter to function?

I probably should start by reviewing how an ammeter is wired-which wires run to and from it....

I knew there would be unintended consequences of a heavier alternator......

It is very kind to help this old country boy from Georgia

The short answer is no. For instance, the horn (looking at the electrical diagram) doesn't go through the ammeter, probably because it's only sporadically that you use, so no real consumption. But if you don't want to run the #6 gauge wire all the way to the panel and back (totally understand you here) you can decide what loads to run to the ammeter and which ones you want to bypass. It will defy the purpose of the ammeter gauge, but not a big deal. In fact, since the alternators began taking over the generators, the ammeter disappeared from the panels. Without going into much detail, in a generator you setup the current output (amps) and you want to make sure you always have some extra looking at the ammeter. In the alternator, what you control is the voltage supplied to it and keep it at a constant 14.5 volts for instance. That job is done by the regulator, but we want to look at that in a gauge.

In a generator, you could have discharged the battery by keeping the lights on without the engine running. Once you start, the ammeter will show just some 4 or so amps at the gauge, and as the battery is charged, the same 4 amps will keep showing. On an alternator on the other hand, once you start the engine, the alternator will try to put as much current as needed and the gauge could show some 40 or 50 amps, but immediately will start lowering that and barely showing a positive reading on the ammeter gauge once the battery is charged. Here's were a voltage meter gauge comes handy, but the Patrol doesn't have one and kept the ammeter just as a remnant of older generator times. Maybe I'm going way of topic here.

If you install an electric winch for instance, you don't want that load to run through the ammeter gauge. Way too much load at once that will move the needle all the way to the negative side. But since it is not a constant load, you are not concerned of its reading.

Edit to add that the new alternator is Voltage Regulator Type: Internal (but not 1 wire capable)
Series: 17SI
I asked if it was 1 wire capable on the product Q and A on the O'Reilly website. In the specs it says its internally regulated. They initially said it was but then corrected themselves with this:

"Hello and thanks for the question. We have received an update from the manufacturer and they state this part number is not one wire capable. The exciter for this alternator is triggered by the ignition and thus needs to be connected to work which means more than one wire is connected to it. We apologize for the mix up."

Not an inconvenience. I think the guide done by member moore_rb covers this:
viewtopic.php?f=28&t=3046&p=29297

[timber]

Thanks again Esteban. I think I understand all you wrote. So how would you recommend I keep some functional utility of the ammeter gauge if I do not route the heavy gauge wire through it?

Tom

[Esteban]

Better said than done…

I’ll have to do a diagram. It might require an additional fuse box.

[timber]

Thanks. Well, reference the photo above of the backside of the ammeter with two hot wire leads going to the same right post on the ammeter? Well I took one lead off the right and put it on the left post but current doesn't flow through. I switched leads on each post and still nothing. I tried it with the key on and still no current through the ammeter. It should function without the engine running or key on, right? My intent was to see the drop when I turned on the loghts.

I must have a bad ammeter. More fun.

After thinking about it, the path of least resistance (pun intended) to using the stock ammeter is to get a smaller alternator (stock alternator) that can use the existing 10 ga wire. Agreed?

[Esteban]

Thanks. Well, reference the photo above of the backside of the ammeter with two hot wire leads going to the same right post on the ammeter? Well I took one lead off the right and put it on the left post but current doesn't flow through. I switched leads on each post and still nothing. I tried it with the key on and still no current through the ammeter. It should function without the engine running or key on, right? My intent was to see the drop when I turned on the loghts.

I must have a bad ammeter. More fun.

After thinking about it, the path of least resistance (pun intended) to using the stock ammeter is to get a smaller alternator (stock alternator) that can use the existing 10 ga wire. Agreed?

Tom, the ammeter is a very simple device. It is just a copper plate that goes from one terminal to the other, so if you have voltage on one, the same voltage should be on the other. When current flows it makes the needle deviate to either side with the magnetic field that is created. It looks that in yours maybe it has been cut. I borrowed a picture from member moore_rb and inserted into your picture of the back of the ammeter.

Tom ammeter.jpg

[timber]

Esteban,
Very observant of you. It has been cut or melted!? I'm not going to waste brain cells as to why. I think I will bypass the ammeter for now in an effort to get the truck running again. Thanks a ton for the sleuthing!

Tom

[timber]

I decided to take the ammeter out of the dash to see what's going on with it. The thing on the backside is just a piece of cardboard type material. Could its function be to protect the magnetic field of the ammeter? I have no idea....

The ammeter was pretty easy to take out of the backside of the dash; just 2 small Phillips screws. My ammeter is inop because the copper coiled wire that the current runs through had melted. The copper wire is spiraled 3x on the bottom and 2x on the top. I think I can cut it out and solder a new copper wire in. How hard can that be? For me.

When I took off the thermostat housing I never imagined I would be monkeying the internals of the ammeter. Also, I decided to try to return the 120A alternator and get the stock one instead. Too many unintended and cascading issues for this light weight. Sisyphus knows.

[jwgreen]

I have some spare Ammeters if you need a new one. Just PM me.