Voltmeter hookup

[woodbutcher]

I bought a tractor that had been converted to a one-wire alternator with no gauge or light to show if it works. I bought a voltmeter at TSC and connected one side to a fused wire from the switch and the other to ground. The light comes on in the gauge when I turn on the key, but the needle doesn't move when the engine is running. When I hold a screwdriver blade to the end cap on the alternator it attracts the metal, so I think it's charging. What's the proper way to connect the gauge?
Butch

 

[JMOR]

(quoted from post at 16:07:00 08/05/08) I bought a tractor that had been converted to a one-wire alternator with no gauge or light to show if it works. I bought a voltmeter at TSC and connected one side to a fused wire from the switch and the other to ground. The light comes on in the gauge when I turn on the key, but the needle doesn't move when the engine is running. When I hold a screwdriver blade to the end cap on the alternator it attracts the metal, so I think it's charging. What's the proper way to connect the gauge?
Butch

Check the info that came with the meter.
Here is a WAG: Both wires go to 'hot', one for light & the other for meter and both light & meter get ground thru mounting.

 

[Double Low Turtle]

Dont do This To see if the alternator is charging simply unhook the positive battery cable while engine is running. If engine dies the alternator is not charging.This is assuming your tractor is a negative ground system.

 

[Bob]

Please don't do THAT!

Disconnecting the battery while running with an alternator system is just asking for trouble.

You may get by with it many times, but sooner or later you will "let the smoke out" of an alternator doing that, from the resultant voltage spike..

 

[Bob]

The meter should read about 12.5 Volts with the engine off, then rise to 13.5 to 14.5 Vollts as the battery comes up to charge. What voltage reading are you seeing?

 

[Keith Williams]

There is another lead to hook to on that meter.
Take the wire you hooked to the ignition switch and hook that to your light switch. Make a third wire and hook that from the ignition to the + side of the voltmeter. That wire should have a fuse in it.
Check your instructions. One of the posts that you bolt the gauge in with may be a + post.
Good luck.
Keith

 

[old]

As Bob says plus if you do that the wrong way and get your self crossed up in the battery cable and to the frame of the tractor doing so can get you dead. An alternator with nothing hooked up can try to charge way more volts then just the normal 14 of so volts and can in fact shoot up to 90 plus volts at 30 plus amp which is enough to kill a person. And as Bob said can/will fry an alternator

 

[Don_G]

If your alternator is the single wire self exciting type you should never disconnect the battery while it is running. This is the type of alternator that comes with most 12 volt conversion kits. Disconnecting the battery will cause the alternator voltage to spike and blow the diode trio in the internal voltage regulator.

 

[souNdguy]

Disconnectiong a running alt is a good way to smoke it..

soundguy

 

[Anonymous-0]

Why don't you check it at the battery? I removed a plug wire with insulated pliers and got a hell of a belt, there was a pin hole I didn't see.took things on face value, hope your driver is A1

 

[woodbutcher]

Thanks for all the replies. I think some may have misunderstood what I said. I don't disconnect the alternator. I simply hold the screwdriver blade or anything made of steel close to the end cap of the alternator. If the endcap(bearing housing) attracts the steel object while the engine is running, that means the alternator is charging. That may or may not be a reliable test.
Butch

 

[Bob]

Magnetism at the rear bearing means the rotating field is energized.

Beyond that, it means NOTHING.

If the stator or the rectifier bridge has failed you will STILL have rotor magnetism, but NO charge.

 

[Michaels Dad]

(quoted from post at 02:19:23 08/06/08) Dont do This To see if the alternator is charging simply unhook the positive battery cable while engine is running. If engine dies the alternator is not charging.This is assuming your tractor is a negative ground system.

Not quite true.
When I was checking out a bad voltmeter I disconnected the alt wire, engine died.
Put a new voltmeter on and it showed charging....don't think the alt. fixed it's self with the addition of a new voltmeter.
Quit buying the expensive ones (2 @ $20+) and bought one for $3.99 at Harbor Freight and it's been working ever since.