Ampmeter connection

[Raider L]

I'm connecting my Autometer amp gauge. This gauge has been in the truck for many years and has never been connected correctly before. I have to say I've been very lazy by leaving it unconnected all these many years. I was doing some wiring work and reinstalling my fuel pressure gauge and I have pulled the instrument panel out and I have the opportunity now and I 'm going to get it working so all my gauges are working. You know negligence is a terrible thing.

The ampmeter's function is to monitor discharge and charging of the battery by the alternator. It indicates recharging of the battery and by what amount depending on the load in amps, and whether or not the battery is holding a charge. It's important if you are going to have one to show the condition of your battery and the charging system. If it indicates a constant discharge something is wrong, and you wouldn't be seeing that on a voltmeter. The voltmeter would indicate normal when the battery is in discharge. The voltmeter shows whether or not the alternator is putting out, not what is going on in the battery while the alternator is charging. That's why I put both a ampmeter and a voltmeter in my truck.

Now I will work on getting it connected correctly and will see how it works together with the charging system.

 

[Raider L]

This is the Autometer instruction sheet for connecting the amp. gauge.
@HotRodPC,
The program won't let me load this photo of the instruction sheet so that I can get comment on the correct method to connect the amp gauge. Why?

I found the problem.. It was how I was uploading the photo. I skipped a step. Sorry. Operator fault.

 

[Raider L]

Let's try this again. This is my Autometer gauge and volt gauge. They are not the "Sport Comp" style gauges. At the time Autometer offered a lesser cost set of gauges. And since I had them already I just kept them after installing all "Sport Comp" gauges for the rest of the set. They will be replaced so I'll have all "Sport Comp" gauges. Autometer doesn't even carry these kinds of gauges anymore. The do carry a set called "Autogage", a less expensive gauge for the budget buyer. But in the meantime we'll work with what we have. The connection is the same anyway as well as the function, range, and accuracy.

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Amp gauge. duh.

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The two together. duh.

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@Ellie Niner, Take a look at the Autometer instruction sheet for the ampmeter install. I really don't want to hook the gauge up to the starter solenoid as in "vehicle system I". I'd rather hook it up to the fuse box down there as in "vehicle system II" shows. I'm probably going to answer my own question I asked in the "wiring hassle" post if the #12 wire I bought would be okay, and it's "NO" it's not sufficient to handle the current as well as what the instructions say to use, a #10 or larger. Holy smoke, what am I to use a dang battery cable on that little post on the back of the gauge? Of course I'm being sarcastic, I don't know where to find wire that large. I'm going to have to go on safari to find it.
What do you think? For the sake of convenience, I do have a small amount of #10 wire but not near enough to reach the battery. But like I said in the "wiring hassle" post I was going to hook one of the wires "B" in the above instructions, "vehicle system II" to the battery side of the fusible link because the battery cable attaches to a #10 wire going to it on the side I would attach the amp gauge one terminal "B" to. Would that be safe? The "A" terminal would attach to the fuse box...where, to what? Obviously I would use another #10 wire to that place. Then everything should be okay...correct?

 

[DoubleDingo]

Back when my old '65, Mean Green was up and running, it had an ammeter, and if my memory hasn't failed me, the wire came off the hot post of the solenoid, and ran to the fuse box, or hot feed for the ignition switch. I took out the ammeter when I replaced the harness in 2004. With the ammeter installed, I know I could disconnect a wire from that gauge and the truck was disabled. I flew to Tacoma, WA in '95 to visit a friend, and to keep my truck safe from being started I disabled it that way before locking it up in the airport parking lot. I didn't wire it in, but I do know it ran with full juice, as the wires fried one night while out cruising around on some backroads. Somehow one of the wires came loose and hit the metal jacket of the heater control cable. That was exciting! That was long before that trip to WA, but it is what made me realize that I could disable the truck by disconnecting the gauge. Thinking about the wire frying, it had to be the wire coming from the solenoid, as it would have juice from the battery.

Edit: Reading the instructions, it appears it is only connected to hot. So mine was connected to the wire coming in from the horn relay. The main feed to the fuse panel on those old trucks is from the horn relay, and it is a #10.

 

[DoubleDingo]

And yes, #10 or #8 wire with a yellow connector.

 

[Ellie Niner]

@Raider L No. 12ga likely won't cut it here. How many amps is your alternator capable of putting out? As the instructions stated in your other thread, size the wire for 10 amps more than your alternator puts out. Unfortunately, this circuit is very critical to the health of your charging system, as every bit of electricity being used or produced (save for the starter motor itself) is flowing into the cab and through this gauge, so it's one area where you can't cut corners. Going too small will result in dim lights, undercharged battery, etc. 10ga should be good for about 65 amps (just barely), and 8ga will take it from there... unless you're getting over 100 amps. In that case, the ammeter would probably be too small for the circuit. They can handle being pegged for short periods of time.

The vehicle system II is for a vehicle with an underhood load distribution center (those boxes with relays and large main fuses on newer cars) near the battery. Unless you've installed something like that in your truck, you'll want to stick with the system I plan.

Must say that this is an interesting install, as I have a thing for instrumentation... If I were going with aftermarket gauges, I would have both a voltmeter and an ammeter as you do here!

 

[Raider L]

@Ellie Niner,

In the diagram above where it says "junction box" isn't that the fuse box down on the firewall where all the wires come through into the cab? So I should look for a #10 red wire like one of that size that goes to the ignition? So, how does the amp gauge work off of two 12 volt power wires connected to it? How does it measure anything?

 

[Raider L]

@Ellie Niner,

Oh man! You mean I'm going to have to wire this thing to the starter?? LOL, dang!

My truck has always had a small alternator in it. Right now I'm using my rebuilt factory alt. that is supposed to be 53 amps. stamped on the housing from the factory, but it does have a new voltage regulator in it and I don't know if that changes the amperage or what. I have a new alternator I bought recently to replace my old one while I was overhauling it. It's a 63 amp. one. I have a MSD multible spark box in the truck tied into my distributor that is a MSD magnmetic pickup type replacing my old point type dist. MSD says NOT to use a alt. of a 100 amps. or more or it will fry the box. My truck has nothing on it taxing the electrical system unless you include the factory AM/FM radio. No extra lighting or anything at all. Yeah, I just thought it made sense to put the volt gauge and amp gauge together. That way I can tell what my electrics are doing at a glance. I'll use a #8 to do this connection.


@DoubleDingo, Thank you! I'll have to wait until Monday and I'll go over to a place called Industrial Electronic Supply where they have all that big a** wire like a #8. I don't think I've ever seen a #8 automotive wire. I thought that #10 I've got was big.

 

[Ellie Niner]

In the diagram above where it says "junction box" isn't that the fuse box down on the firewall where all the wires come through into the cab? So I should look for a #10 red wire like one of that size that goes to the ignition? So, how does the amp gauge work off of two 12 volt power wires connected to it? How does it measure anything?

^ Perfect. You'll be good to go with 10ga.

Technically, yes, the fuse box is the junction box on your truck, but it's too far away from the battery in our trucks to be used as the point where the alternator connects to the battery.

Though it's not 100% accurate, it's easier to visualize if you think of the electrical system as a water system, like household plumbing... the ammeter measures water flow between the alternator and battery. The more water is flowing from the battery to power things, the more the needle deflects toward "discharge". The more the alternator is putting out to recharge the battery, they more the needle points toward "charge". Once the battery is topped up and the alternator is able to meet demand, the needle stays centered. The voltmeter measures the water pressure. The alternator is a water pump, and the battery is a water storage tank. And to finish it off, the ground side is sort of like a sewer, where the used water flows to start the cycle all over again.

 

[Raider L]

@DoubleDingo,

Like these? I think these are #12-10.

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Now, this is that wire I have that I believe is #10. It's the biggest wire I've got.

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And I think this is #12. You can see it's a lot smaller than the wire above.

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This is my electrical box. All my connectors on the left down to either #00 ring connectors. I mean they are tiny. I'll take a pic of them in a minute.

 

[Raider L]

@Ellie Niner,

That's a excellent explination. That's what I tried to describe above. I'll bet once my amp gauge is hooked up I actually may be able to catch that little glich when I can't start the truck until after I clean the positive post on the battery and then it cranks like nothing happen, which is what started all these post about the battery and the rest. I'll run out to the truck and try to take a pic of what I was talking about hooking "B" to where the positive battery wire attaches to the starter wire on the battery side of the fusible link. Give me a sec.

 

[Raider L]

@Ellie Niner,

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Boy this is about as close to "real time" as I can do. Here is where I want to connect the amp. gauge up to instead of going all the way down to the starter. What do you think?

The large red cables are:
1) Starting with the big bolt in the middle, excluding the #12 red wire to the left of the big bolt, the big red cable IS the battery cable. That big bolt is a bronze bolt and nut.
2) The next large red cable to the right IS the power cable going to the starter.
3) On that same big bolt, the wire that is up at an angle is 12 volts going into the electrics in the cab through the fuse block. That's the one that curls back up to the fusible link on the firewall I was going to use.
4) To the right of the big bolt is a sticker marked "S" is the purple wire going to the starter.
5) Next to it with a sticker marked "R" is one of the starter wires I think that is part of the fusible link down there. I was told by Autometer to put a shunt on this wire so as to stop any back flow of electricity while the starter is stopping, to protect the system. I haven't had any problems from it so far and it's been 25 years so I guess they knew what they were talking about.
All those wires on those posts, "S", "R" go inside the cab to the starting wiring.

 

[Raider L]

What would work better a ring connector or would these work? I know they are for what, a #12-14, isn't that a blue connector? But this type but for a #8 wire of course.

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Slip on's?

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My electrical box.

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One of my small parts wall.

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Need some auto light bulbs? I have a light for all the cars even those little tininesy console bulbs. I'm going to have to go out to the wrecking yard and get some of those little bitty bulb sockets for those mini-bulbs.

 

[DoubleDingo]

Ring connectors for sure. And sized correctly for the studs on the gauge.

The others explained everything else way better than I could

 

[Raider L]

This is still "Electrical" but I thought you all might be interested in seeing this.

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The connector on the left is a #14-16 ring connector. The one on the right is...I don't really know, maybe a #00 like I was talking about in text above. But you can see how small it is. If somebody knows what size this ring connector is, chime in.

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The red wire is a #16 wire, I believe, and I thought the orange wire, on the right would fit but it was to large and wouldn't go through.

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So I found a wire about half the size of the orange one, and it did go through. I don't know what size little wire that is. You can see how the end of the orange wire is jammed up so it wasn't about to go in like it should do. But I pushed gently on the little red wire and I could see it come through towards the ring.