Installing amp meter on 8N

[trying2mow]

Please tell me how to wire in an amp meter on my tractor(8N). Do I hook it in series with the pos terminal of battery? If so will I have to put a giant wire in to carry the starter load? Thank you!!

 

[Bruce (VA)]

Goggle " wiring diagrams JMOR". Find the
schematic that fits your tractor, voltage &
ammeter type.
75 Tips

 

[Del Huebner]

On the early 8N the 10-12 gauge wire comes off the solenoid and thru the ammeter to the hot terminal on the resistor. Picture of one I just did using JMOR pictogram as a guide.

 

[Bill Crowell]

An ammeter can be inserted into either the positive or the negative leg of a DC circuit because, under Kirchoff's law, the current flowing in any circuit is the same everywhere in the circuit. It just needs to be wired with the opposite polarity when inserted in the negative leg of the circuit, as opposed to the positive leg. In the electronics industry, and in a normal (negative ground) DC circuit, they always install an ammeter in the negative leg because then you don't have to worry about shorting the meter terminals to ground and burning something up, or getting a bad shock when you try to adjust the meter movement. In the 8N charging circuit (positive ground), they followed this accepted practice. Ford wired it into the positive leg of the circuit because the positive leg is at ground potential.

 

[JMOR]

(quoted from post at 16:48:14 11/18/16) An ammeter can be inserted into either the positive or the negative leg of a DC circuit because, under Kirchoff's law, the current flowing in any circuit is the same everywhere in the circuit. It just needs to be wired with the opposite polarity when inserted in the negative leg of the circuit, as opposed to the positive leg. In the electronics industry, and in a normal (negative ground) DC circuit, they always install an ammeter in the negative leg because then you don't have to worry about shorting the meter terminals to ground and burning something up, or getting a bad shock when you try to adjust the meter movement. In the 8N charging circuit (positive ground), they followed this accepted practice. Ford wired it into the positive leg of the circuit because the positive leg is at ground potential.

very long time ago, I took an exam and the professor wrote that "you should have stopped before adding that last sentence, which demonstrated that you lacked the understanding that you had shown mastery of up to that poin", which made what otherwise would have been a correct answer into an incorrect answer. Same here, Bill......should have stopped before, " In the 8N charging circuit (positive ground), they followed this accepted practice. Ford wired it into the positive leg of the circuit because the positive leg is at ground potential."

 

[Bill Crowell]

Oops, JMOR, do you mean that the ammeter is really in the negative side of the circuit? If so, MY BAD!

 

[Bill Crowell]

Oh yeah, I just realized that of course the positive battery lead goes directly to the chassis without passing through the ammeter. I am dumb. Sorry!

 

[JMOR]

(quoted from post at 17:58:39 11/18/16) Oops, JMOR, do you mean that the ammeter is really in the negative side of the circuit? If so, MY BAD!

es. On those tractors, about the only way I see to put the ammeter in the grounded (positive side) circuit is to get a really big one, about 200-400amperes, so that it can handle starter current. But one that could read that size current would scarcely indicate 3-4 amps of charging current.

 

[trying2mow]

(quoted from post at 11:02:24 11/18/16) On the early 8N the 10-12 gauge wire comes off the solenoid and thru the ammeter to the hot terminal on the resistor. Picture of one I just did using JMOR pictogram as a guide.

y old 8N was converted to 12V and has a neg ground. My set up looks different than your pic. I do have one long ceramic resistor. I guess I go from solenoid through meter to the resistor but which end? thanx

 

[Royse]

(quoted from post at 00:15:18 11/19/16)

(quoted from post at 11:02:24 11/18/16) On the early 8N the 10-12 gauge wire comes off the solenoid and thru the ammeter to the hot terminal on the resistor. Picture of one I just did using JMOR pictogram as a guide.

y old 8N was converted to 12V and has a neg ground. My set up looks different than your pic. I do have one long ceramic resistor. I guess I go from solenoid through meter to the resistor but which end? thanx

I'll echo Bruce's statement. Google JMOR's wiring diagrams.
They're the easiest out there to picture and he has them for
12V conversions. Most likely like yours too.

If you have a key start setup I would like to see what you have
before I made recommendations so I didn't steer you wrong.
If it all works but the ammeter indicates the wrong way, swap
the wires on the back of the ammeter.

The starter wire, big heavy cable, should NOT run through the ammeter.

 

[Philco]

On my 1951 8N 12 volt conversion tractor, negitive ground system, I installed a new ammeter purchased from a Ford tractor dealership. The needle flutters but doesn't move from zero. This is how I hooked it up. hooked up; The single wire from the alternator connects to the positive side. The other wire coming from the solonoid from where the battery cable connects, is attached to the negitive side. The ignition key yellow wire is attached to the ammeter positive side. I also switched the wire opposite on the ammeter and got the same result readings as the needle did not move beyond zero. Is this correct? Thanks guys for your helpful responses.

 

[Jim.ME]

This is a 2016 thread, you are often better off to start your own new thread, after researching ones like this. People tend to read the original post and answer the questions posed there and miss seeing your late arrival.

How much an ammeter needle moves can be affected by the scale of the ammeter, condition of the battery, load on the system, and condition of the alternator. Wired as you have it (correctly battery on one terminal load and charging system on the other terminal) the ammeter only shows the current coming from or going to the battery. Have you checked battery voltage at the battery posts when off and when running? Is the alternator belt tight? With only the ignition for load and if the battery charge is up, there isn't much current passing back to the battery. What is the scale of the ammeter?

Some will disagree but this is where a voltmeter gives a better reading of the electrical system than an ammeter, in my opinion.

 

[Btzj02]

I have one alternator that starts charging immediately at engine start. I have a second alternator that does not start charging until the engine RPMs are increased above 1200. Both tractors will show about 8 to 10 amps charging, once they start charging, for a few minutes after engine start. After the first few minutes the needle returns to zero and bounces around zero.

 

[MeanGene1]

I have two 12V alternator kits from this site, good brackets, and they both charge at low rpm without having to be revved up. The purists will scream, but both the late 8N and the 850 are set up with car solenoids and key switch starting, and both work very well. This allows me to keep one spare solenoid for all my stuff