Ammeter question....

[BertZegers]

Just got back from starting the tractor.

Side note.... as I understand, the stock alternator (in amp size) was no longer available.... so instead of having (let's say) a 90 amp (50?) alternator, I have a 110 amp alternator. Whatever the original size in output was, this new one is slightly more. AND all the lights except for the dash lights were replaced with LED's so the way I see it, I have more juice available from the alternator however, I have collectively, smaller demand.

(don't know if that matters to know or not)


Anyway, just went out, put both batteries in (two 12V long skinny type verses two 6v).

The lights, all of them, work totally as expected EVEN WITH THE KEY OFF. Turn light switch, and they come on.

During this non-running time, I was staring at the (again, brand new) ammeter and though the engine was OFF, it didn't budge at all. Didn't slide upwards, nor did it slide downwards. It was as though it was simply dead.

(side question..... all lights are now LED's, would they draw enough power like that to make it show??) I would deduce they must show since they show the change from "+1 to +3". Interesting.


Started the engine and AT IDLE, the ammeter just sat there, pegged at zero. Once I revved the engine a bit, THEN it perked up and went to (let's say) +1. When I turned the lights on, then it went to (let's say) +3.

Turning key off/back on had no effect on the meter, even while engine running.

However, after reading all this info (which is fantastic by the way), I'm now curious if maybe I don't in fact, have a wire hooked to point "B" instead of point "A"....

I don't think I've EVER witnessed the meter showing anything less than zero and typically, it's at the +1 mark because I don't do anything yet requiring any lights.

Your Amp meter must be in the charging system and therefore reeds alternator output Amps.

( On my tractor the Amp meter is in the wire from battery to ignition switch, and should read amperage going in or out of the battery ( except for starting ))

The Amp meter is an "indicator" and does not have to be very accurate.
Amp meters can be wired in different on tractor makes or models.

I assume that the Amp meter was important when tractors still had a DC generator, and the Amp meter showed charge. A tractor running idle, with lights on, could drain the battery.
Alternators usually keep up with all the factory installed lights and accessories and a volt meter gives a better indication of the health of the system, for the people who know how to interpret the reading.
Usually a light is enough to to show if the system is working or not.

 

[rScotty]

My expectation on how this would work WAS:

Start machine, that costs you some battery power. So, as machine is running, the ammeter SHOULD show NEGATIVE and as the battery returned to a full charge, the needle would tend towards zero.

What I EXPERIENCED: Start machine, needle jumps to (let's say) +1.... turn lights on (bigger drag on system) and the needle goes to (let's say) +3 HOWEVER, the more it runs, the more I expect it to DWINDLE DOWN to zero indicating that the system isn't now charging the battery as much.

So though I think I "got it", I got it from the wrong perspective. I think I was describing more the workings of volt meter rather than ammeter. Reasonable???

Well almost.... A voltmeter would work that way if you started the engine and then immediately turned it off. That is, it would show that the battery is able to put out slightly fewer volts than it could before you started the motor. It might have dropped from 12.3 to 12.2 for example. However, as soon as the motor is started, the voltmeter is reading the average voltage in the entire circuit. That includes the alternator output voltage which is now spinning and charging the battery with something a little bit more than 13 volts. So the voltmeter will show the average of the slightly depleted battery and the alternator charging at a higher voltage.

Sometimes it helps to thing of the two aspects of electricty as being similar to a flow of fluid. Voltage is like the pressure (psi) in the hose, and amperage is like the total quanitity of flow (gallons per minute) of the fluid.....or of the electricity.

You measure voltage by putting the meter in parallel with the circuit. That means you measure voltage with one wire from any one point and the other wire to frame, which is considered to be a stable "ground". One side of every single circuit in your tractor is always connected to grounro voltage in a tractor is not usually no volts. It is just not enough pressure to be useful.

You measure amperage by putting the meter in series with the circuit. Basically you cut a wire and insert the meter. This is how amperage of flow is measured, and just like any kind of flow it can flow in one direction or the other.....which is why zero is in the center of the ammeter. It is not only showing you the amount of flow, it is showing you the direction.
Rscotty

 

[BertZegers]

My apologies.

I rewired the entire tractor (brand new harness).... IF I recall the instructions correctly, there was a wire that came back from the alternator and another wire that came up from the starter/solenoid. As I recall, it bridged these two items. What I was wondering at the time was do the wires go "A/B" or "B/A" and did I have them backwards. I put them in as per the instructions.... I just had an uncertain feeling in the back of my head.



Well... I thought I still had the harness installation instructions. If I do, I can't find them yet.

I don't know WHICH wire that may have come from (presumption from the alternator) but I'm 99% sure the other end went to the battery.

I have found a schematic from the IH 1066 Hydrostatic;
https://cdn.compknowhow.com/carterandgruenewald/wiring_diagrams/IH 66 SERIES.pdf

The + from starter (battery) goes to plus on Amp meter, the minus from the Amp meter goes to alternator "B".

It looks to me that the Amp meter shows the lights current from the battery when the tractor is not running and key switch of , and the amp meter shows charging amps only when tractor is running

Than there could be a situation that current is drawn from both battery and alternator, than the reading does not making sense. (full battery and low RPM ?, )

 

[Richard]

Good stuff.....thanks to all.

I think, well, I KNOW I'm not going to touch this during winter!!! (don't like cold). I think I'll perhaps dig into this more once spring arrives. I don't want to say this for sure, but I think there were several wires that attached to the rear of the meter. One large one (I presume 12g) and if I recall, a smaller one. I don't recall if there was one smaller one on one side or if both sides had a second, smaller wire.

What I DO have floating in the back of my head as a distant "is that what I recall happening....." is that I had some issues fitting the wires onto the screw lead coming out of the meter.

If THAT is where one puts it "on the battery" verses "on the alternator", then that would make some sense to me as getting the meter wired up was something I had to fiddle with and if I recall, had to take apart and do again. It's possible that I crossed something.

None the less.... today, not a worry for me. Come spring, I might see if I can trace down the smaller wires.

Again, thanks to all.

 

[Fuddy1952]

The schematic for the IH1066 is available online, and looking at it, it's complex especially for the year (1971 to 1976 I believe it says). Add to that cut, disconnected wires, bulbs replaced with LEDs, etc. and it's a mess.
I was going by initial post "I did a full harness rewire last winter/spring. (new harness, new ammeter / instruments, new lights, batteries, ignition switch.... virtually EVERYTHING except for the tach and water/oil info. I even replaced the button for ignition and the other button for the ether."
So I assumed completely rewired back to factory stock.
Again, I'm thinking about 45 years ago, that tractor. In use you're only concerned with a few things when looking at gauges...rpm, does it have oil pressure, is it charging, etc.
Back in the shop you can check batteries, voltage, etc.
Like lots of cars back then (and pre 70s) had "idiot lights" key on...they all light. Start motor...all should go off. You don't care running if oil pressure is 30 or 45, or if battery voltage is 12.8 or 14.1, you just care that you have pressure and it's charging.
We collect old cars. My wife has her first car, a '55 Chevy her Mom bought new. Original drivetrain and wiring...not one LED light anywhere. My thought is whatever you have, tractor, car, truck it is what it is. If you want to "upgrade" (I hate that word)...just buy new.

My opinion is you have a good tractor, I'd just have it back like it was. Like schematic Dale shows, everything starts with the batter(ies). Battery + positive to ammeter + positive. Ammeter -- negative side to ignition switch ("everything else" so to speak).

 

[Fuddy1952]

Great explanation Fuddy. I've often heard the water/electricity comparison and believe it to be valid.

I'd agree to put the tractor back like it's been since inception.

So,,, makes me wonder,,, why do they now use volt meters?

"So,,, makes me wonder,,, why do they now use volt meters?"
Complexity IMHO.
With computers, complex circuitry, voltage is more important and critical. A new tractor a meter with "D" and "C" on it wouldn't mean or tell you much.

What I was told in electronics school another lifetime ago was all meters are ammeters. All! So you had a multimeter with lots of voltage, current, resistance ranges...but one ammeter. To measure current, you switched in different resistors across meter (shunts). To measure DC voltage you switched in different resistors in series so the meter was measuring current flow through the resistor (voltage = current times resistor). To measure resistance the meter had it's own battery, again switching in resistors so (resistance=voltage/current).
Airplanes ammeter had the shunt resistor near battery, two small wires off of it to ammeter in cockpit. Safety...so if meter failed it didn't matter, you still had the low resistance shunt in the battery circuit.
Trivia...

 

[Fuddy1952]

I left out multimeter to measure A.C. voltage meter had diodes to convert a.c. to dc then measure. Multimeters use precision resistors for accuracy.

 

[ovrszd]

"So,,, makes me wonder,,, why do they now use volt meters?"
Complexity IMHO.
With computers, complex circuitry, voltage is more important and critical. A new tractor a meter with "D" and "C" on it wouldn't mean or tell you much.

What I was told in electronics school another lifetime ago was all meters are ammeters. All! So you had a multimeter with lots of voltage, current, resistance ranges...but one ammeter. To measure current, you switched in different resistors across meter (shunts). To measure DC voltage you switched in different resistors in series so the meter was measuring current flow through the resistor (voltage = current times resistor). To measure resistance the meter had it's own battery, again switching in resistors so (resistance=voltage/current).
Airplanes ammeter had the shunt resistor near battery, two small wires off of it to ammeter in cockpit. Safety...so if meter failed it didn't matter, you still had the low resistance shunt in the battery circuit.
Trivia...

My offroad buggy uses a Volt Meter. It comes in handy when doing serious winching. If I run the system voltage down too low the computer will shut off the vehicle. I can watch the Volt Meter and know when I'm approaching that issue. An engine stall because of low voltage while hanging on a winch cable is not good.....

 

[RickB]

Volt meters began showing up on tractors in the very late 1970s and early 1980s. Fact of the matter is, the OPs 1066 was replaced by the 1086 which included a voltmeter, not an ammeter in the instrument panel.

 

[WranglerX]

My offroad buggy uses a Volt Meter. It comes in handy when doing serious winching. If I run the system voltage down too low the computer will shut off the vehicle. I can watch the Volt Meter and know when I'm approaching that issue. An engine stall because of low voltage while hanging on a winch cable is not good.....

Yeah.. Dropout voltage in my Jeep is about 9 volts... 100 amp alternator can not keep up with winch...Fortunate large Odyssey battery will come back to life if it sits about 15 minutes to allow me to start Jeep...

Dale