trying2mow
Member
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!!
- Thread starter trying2mow
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Bruce (VA)
Well-known Member
Del Huebner
Member
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
Member
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
Member
Oops, JMOR, do you mean that the ammeter is really in the negative side of the circuit? If so, MY BAD!
Bill Crowell
Member
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!
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
Member
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(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.
I'll echo Bruce's statement. Google JMOR's wiring diagrams.(quoted from post at 00:15:18 11/19/16)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(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.
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.
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