Farmall M ammeter randomly spiking

[706man]

I have an ammeter on my M that spikes randomly(to the right). I bought the ammeter last year and thought I hooked it up right. It has always kind of maxed out randomly since I put it in. It doesn't stay spiked long. When it doesn't max out it stays about one line to the right of center. I have one side of the ammeter wired to the + batt wire side of the foot push starter. Other side of ammeter goes straight to the bat side of alt. Along with the headlight wires, etc.
Since I "believe" it is hooked up right, might I have messed up the ammeter in any way possibly having the wires hooked up wrong at some point? Thanks!!

 

[wore out]

Comments removed as they didn't apply to the tractor having an alternator, a minor detail the O.P. left out of his initial post!

 

[706man]

This is a converted to 12v system.

 

[used red MN]

This is a converted to 12v system.

What type of alternator was installed, brand, a 3 wire or 1 wire? If an internal regulator type the spiking almost has to be caused by a momentary failure of a circuit in the regulator. Or something is shorting to ground on your wire between the ammeter and foot switch or the positive battery cable, none of that would last very long without a smoke show reporting it.

 

[Janicholson]

What type of alternator was installed, brand, a 3 wire or 1 wire? If an internal regulator type the spiking almost has to be caused by a momentary failure of a circuit in the regulator. Or something is shorting to ground on your wire between the ammeter and foot switch or the positive battery cable, none of that would last very long without a smoke show reporting it.

Also if this alternator puts out 35 amps (or much more is possible) the meter may be pegging from that issue. a greater amp range meter is needed in that case. Jim

 

[706man]

What type of alternator was installed, brand, a 3 wire or 1 wire? If an internal regulator type the spiking almost has to be caused by a momentary failure of a circuit in the regulator. Or something is shorting to ground on your wire between the ammeter and foot switch or the positive battery cable, none of that would last very long without a smoke show reporting it.

Delco-Remy, 3 wire. The blue wire coming off the ammeter is the blue wire attached to alt. Red wire on ammeter to pos batt cable foot switch has nothing wrong with it. Could the light switch connections be causing issues. Lights work, just need to wiggle the round dial light switch until they turn on. Probably should get a new light switch comp sometime.

 

[Jim Becker]

How many amps is the alternator and what is the max reading of your ammeter? "Maxed out" may be 21 amps.

Maybe your light switch that needs a little wiggling is occasionally shorting to ground. Try unhooking the wire that feeds the light switch (or simply removing the fuse) and see if the behavior goes away.

 

[used red MN]

Could the light switch connections be causing issues.

Doubtful, anything on that side of the ammeter would cause it to show a discharge. I see someone else is replying, we’ll see if he says the same thing.

 

[706man]

Jannicholson, that is what I have thought for a while. Amperes only goes to 20 on ammeter.

 

[Jim Becker]

Doubtful, anything on that side of the ammeter would cause it to show a discharge. I see someone else is replying, we’ll see if he says the same thing.

Good point. Any added output from the alternator in response to a current draw in the light circuit would not go through the ammeter. Problem nearly has to be in the alternator. Could also be a bad connection on the sense wire that feeds the output voltage back to the regulator.

 

[706man]

Unhooked the wire that runs to fuse/then headlight component. Started tractor and ammeter gauge was then "pegged full time". Left the black wire on ammeter that runs to back of pull switch.

 

[706man]

If indeed you all agree I have it hook up correctly, then probably these two things would solve all issues?

 

[Jim.ME]

If indeed you all agree I have it hook up correctly, then probably these two things would solve all issues?

From the descriptions you have given, they need to be done anyway and may solve the issues.

 

[706man]

Well then I am hoping there was/is something a little wrong with the current lite switch. So after unhooking that last wire I was asked to do and what my result was. What does that tell?

 

[Jim.ME]

If wired with only the battery wire on one terminal of the ammeter and all others wires (alternator output and all loads) on the other terminal of the ammeter, the alternator output would be delivering power to the same terminal the light switch gets power from. Some power could be going to ground through the light circuit and part through the ammeter and to the battery. With the wire to the light switch unhooked from the ammeter it would look like more amperage is going through the ammeter to the battery, indicating a draw from the unhooked circuit. You posted you have to wiggle the switch to get the lights on, a sign there may be problems inside the switch.

Are the insulating washers around the ammeter terminals good?

 

[560Dennis]

Why is there the huge eyelet over to the light switch bridge ?

 

[Jim.ME]

Why is there the huge eyelet over to the light switch bridge ?

Good on spotting that, it could be an issue

.

 

[706man]

Yes they are. The ammeter is brand new. Bought last year, but tractor stored in garage. The light switch is original equipment on the tractor. So it definately has to go. Thanks for the explanation.

 

[706man]

Whoa I did not see that. That could save me $50. Although now I still want a new headlight switch. I am going to look at it now. Thanks!! Will let you know.

 

[706man]

I separated those two connectors touching. Nothing different happening. But can you tell me if all the wires on the light switch are right? The lights are live. They turn off with the light switch but I don't have to tun on the pull switch to turn the lights on. So I have to have the lights wired wrong somewhere. And the amp gauge still maxed out.