I just purchased a new amp meter for my M. My tractor has a 12 volt, one wire alternator. A couple of years ago the gauge quite working but I get about 14 volts when running the tractor so I figured the alternator is OK and the issue is the gauge. I disconnected the battery before I started. Just the process of installing the meter made the needle move. I can tap it back to any place I want. First installation the hand went all the way to +20. After I disconnected all the wires and reinstalled I watched go all the way the other side. Can anybody explain whats happening.
- Thread starter Charlie M
- Start date
Bob M
Well-known Member
Charlie - A couple possibilities:
1 - If you can "tap" the ammeter needle to any position is says the new ammeter is defective (ie. the movement is sticking). A good ammeter will center itself at O almost instantly with no current flowing.
2 - If the ammeter deflects either direction when you make the battery connection you've got current draw somewhere. Could be as simple as the light switch left on. However a bad alternator (failed diode or regulator) will also do it. Also a short somewhere in the wiring.
Note also: If the needle defects to the + (charge) side when you connect the battery, is means the connections to the ammeter are reversed. Solution is to swap the wiring at the two ammeter posts.
1 - If you can "tap" the ammeter needle to any position is says the new ammeter is defective (ie. the movement is sticking). A good ammeter will center itself at O almost instantly with no current flowing.
2 - If the ammeter deflects either direction when you make the battery connection you've got current draw somewhere. Could be as simple as the light switch left on. However a bad alternator (failed diode or regulator) will also do it. Also a short somewhere in the wiring.
Note also: If the needle defects to the + (charge) side when you connect the battery, is means the connections to the ammeter are reversed. Solution is to swap the wiring at the two ammeter posts.
Janicholson
Well-known Member
On your note, to the poster, not you Bob!! I would add that if nothing is on and you connect the battery the needle should not move at all. If (with the tractor off) the needle moves toward charge (right) when the lights or ignition is turned on, the meter is backwards. Jim
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