re-wiring ammeter

pierce · Aug 1, 2013

so, near as I can tell, the ammeter from my ratty 1948 8N is intact. the needle bounces freely, stays centered on zero... when I remove the shunt/clamp (I'm assumign the clamp piece doubles as the current shunt, and has to be insulated from the back of the front panel?), I measure about 3 ohms across the meter movement, which sounds about right.

my tractor is wired very crudely, see
[u:5967a0f31f][b:5967a0f31f]http://freescruz.com/8nTractorWiring.pdf[/b:5967a0f31f][/u:5967a0f31f]

I am guessing I can just put the ammeter in series with the alternator, using suitably heavy wire? (existing wire that goes to teh alternator instead screwed onto one side of the ammeter, and a new wire from the other side to the alternator B+ ?)

Bruce (VA) · Aug 1, 2013

Why guess? Why put up w/ a p1ss-poor wiring job that's likely to be both unsafe & unreliable? Google "JMOR wiring diagram" & do it correctly (tip # 42).
75 Tips

pierce · Aug 1, 2013

actually, the way this tractor is wired is very straightforward, and quite functional. its just not the way I've seen it done on any other schematics, its much simpler. there's nothing unsafe about it.

ARCO petee · Aug 1, 2013

a nice function of an ammeter is the ability to show negative charge or battery drain. If you wire in series with the alt you will not see ignition drain when the tractor is not running or the alt is not functioning. For the negitive to work the meter must be in series with the battery.

pierce · Aug 1, 2013

(reply to post at 13:36:45 08/01/13)

good point. so I should put it in series with the lead from the solenoid to the run switch (see my unconventional schematic linked above)

I'm still a little fuzzy on the actual ammeter connections... the inputs are the two mounting bolts? and the metal clamp piece doubles as the shunt? what is normally used to insulate that clamp piece from the back of the dashboard? and the double loop on the lower back of the ammeter, thats just for securing wires, and serves no electrical purpose?

Paul in Edmonton · Aug 1, 2013

The alternator on the 8N has no direct electrical connections at all, believe it or not. The wire you want to measure the current through goes through the loop on the back. The wire should be properly insulated. That's it. No connections.

It works on an induction principle. Every used a clamp-on ammeter? Same principle.

-Paul

pierce · Aug 1, 2013

whack, I thought inductive ammeters only worked for AC not DC current. but, hoookay...

so which way should the wire go through the ammeter? battery on the left side, alternator on the right as looking at the meter from the back? I know getting this backwards would just mess up the polarity, but I'd prefer + == charging, and - == discharging, just because thats 'normal'.

Paul in Edmonton · Aug 1, 2013

(quoted from post at 21:43:05 08/01/13)
whack, I thought inductive ammeters only worked for AC not DC current. but, hoookay...

I've got two clamp-on ammeters. The expensive one does both AC and DC. The cheap one ($10 for a digital multimeter!) only does AC. It's actually still in the box-- it was only after I got it home that I realized it was only good for AC. I had bought it for my brother-in-law to tell if he had current leaks in his trailer, after showing him how well my other one worked for that...

As for direction: the logical routing for the original set up gives a positive reading for charging. By logical routing, I mean the expected routing of the wire from the resistor block, through the loop, to the solenoid.

-Paul

JMOR · Aug 1, 2013

(quoted from post at 16:43:05 08/01/13)
whack, I thought inductive ammeters only worked for AC not DC current. but, hoookay...

so which way should the wire go through the ammeter? battery on the left side, alternator on the right as looking at the meter from the back? I know getting this backwards would just mess up the polarity, but I'd prefer + == charging, and - == discharging, just because thats 'normal'.

believe what you said is correct for original pos gnd system, but backwards for your neg gnd alt setup. Further, I believe Paul described what you need, not the original setup for pos gnd.

Hobo,NC · Aug 1, 2013

When your tractor won't crank won't start knocks off that stupid amp meter will set their right on 0 and tell you nuttin about the battery are the health of you electrical system,,, replace it with a volt meter....

willie in mn · Aug 1, 2013

You are almost there. The U shaped metal bracket is for mounting only, it is not a shunt. There should be insulated bushings & washers to isolate the bracket from the bolts/posts. After securing the ampmeter with brackets & nuts, the wires are secured with a second nut & washer on the posts.
HTH
Willie

pierce · Aug 1, 2013

except, I think the other poster, Paul in Edmonton, was correct, this is a inductive ammeter, not a direct connect one. the holes in the metal bracket are just too small to allow for such rubber isolation washers.

I forgot to get a couple feet of heavy gauge wire today, so it will have to wait until tomorrow

pierce · Aug 1, 2013

if the tractor doesn't start, I can break out my DVM that I keep handy, and test the battery directly.

I actually picked up a 2" voltmeter, but it just doesn't look right on that old tractor. maybe I'll install it on a panel under the top battery/fuel access so I can check it when I need to.

Bob · Aug 2, 2013

A "wireless alternator", eh?

I LIKE that concept!

Tim Daley(MI) · Aug 2, 2013

The original 'loop' style ammeter is an induction
type used with the original 6-volt/positive ground
set up. The large yellow wire (original wiring
harness)feeds thru the loop on the back of
ammeter. If gauge shows backwards operation,
reverse the direction of feed thru loop. Later
aftermarket ammeters have the screw terminals. You
would simply cut the large yellow wire and connect
one end to one terminal and the other other end to
the other terminal. If operation shows backwards
function, reverse the wires. Simple. There are NO
OTHER electrical connections. What you are calling
the 'clamp current shunt' is just the mounting
bracket. It has no active function for current or
a ground.

By the way,if you get a voltmeter I would be
interested in buying your old loop ammeter as
shown in your picture.

Tim 'PloughNman' Daley

Now, since you have a 12-volt cobble, er, I mean
conversion, it is better to have a VOLTAGE GAUGE
connected.

pierce · Aug 2, 2013

well, whichever way I hooked it up the first time, hah, I had it backwards, so - was charging. clipped off the terminal on the switch side, fed wire through other way, recrimped, and voila, now get a reading of about +20A for a few seconds, once I revved it up to about half throttle so the alternator starts, and dropping to 0A within 10 or 15 seconds. this tractor is starting on pretty much the first crank, with no choke, even when cold..

hey, I'm using the alternator pulley that came on this rebuilt delco 10SI, it was the same size pulley as was on the old dead 10SI... should I be using a smaller one so I get more RPMs out of the alternator, or just not worry? this replacement alternator is 65 amps or something so as long as I bump the throttle to bootstrap the alternator, all should be good, eh?

Hobo,NC · Aug 2, 2013

(quoted from post at 02:54:07 08/03/13) well, whichever way I hooked it up the first time, hah, I had it backwards, so - was charging. clipped off the terminal on the switch side, fed wire through other way, recrimped, and voila, now get a reading of about +20A for a few seconds, once I revved it up to about half throttle so the alternator starts, and dropping to 0A within 10 or 15 seconds. this tractor is starting on pretty much the first crank, with no choke, even when cold..

hey, I'm using the alternator pulley that came on this rebuilt delco 10SI, it was the same size pulley as was on the old dead 10SI... should I be using a smaller one so I get more RPMs out of the alternator, or just not worry? this replacement alternator is 65 amps or something so as long as I bump the throttle to bootstrap the alternator, all should be good, eh?

Is this a trick question... you have a amp meter that will tell you nuttin about the alt pulley,,, if you have issues drag out yer DVOM....

pierce · Aug 3, 2013

(quoted from post at 18:55:12 08/02/13)
Is this a trick question... you have a amp meter that will tell you nuttin about the alt pulley,,, if you have issues drag out yer DVOM....

nah, did that already, its charging fine once you rev it to about half throttle. with a smaller pulley, the alternator would kick on sooner, but its good enough the way it is.

re-wiring ammeter

pierce

Member

Bruce (VA)

Well-known Member

pierce

Member

ARCO petee

Member

pierce

Member

Paul in Edmonton

Member

pierce

Member

Paul in Edmonton

Member

JMOR

Well-known Member

Hobo,NC

Well-known Member

willie in mn

Well-known Member

pierce

Member

pierce

Member

Bob

Well-known Member

Tim Daley(MI)

Member

pierce

Member

Hobo,NC

Well-known Member

pierce

Member

Similar threads