Ammeter not working.

dahermit · Sep 12, 2014

1948 8N, ammeter has not worked for some time.
Bought a new one and it does not work either.

See attached wiring diagram. The Ammeter needle does
not move from zero when running.I get no voltage
across "A" to "B" with engine running. On the
Ammeter, I get 6 volts between terminal "A" and
ground and 6 volts between "B" and ground with the
engine running. What is the likely cause/fix?

JMOR · Sep 12, 2014

(quoted from post at 14:39:04 09/12/14) 1948 8N, ammeter has not worked for some time.
Bought a new one and it does not work either.

See attached wiring diagram. The Ammeter needle does
not move from zero when running.I get no voltage
across "A" to "B" with engine running. On the
Ammeter, I get 6 volts between terminal "A" and
ground and 6 volts between "B" and ground with the
engine running. What is the likely cause/fix?

our attachment didn't make it

dahermit · Sep 12, 2014

Photo did not load, will try again.

JMOR · Sep 12, 2014

(quoted from post at 14:45:37 09/12/14) Photo did not load, will try again.

K, BUT........where are VR/generator/alternator connections in your diagram? It matters, if you want ammeter to indicate charging current.

Paul in Edmonton · Sep 12, 2014

There should be no voltage drop between A and B and the voltage from each to ground should be the same. That part is okay. As to why it's not reading anything, that is a problem. Bad ammeter is one possibility if everything else is hooked up properly.

-Paul

greywolf224 · Sep 12, 2014

True but he is on his second ammeter.
Really dependent on where that Battery wire from the VR and the wire from the 6volt battery are connected to or where that junction point is. If not through the Ammeter all bets are off.

souNdguy · Sep 12, 2014

bat terminal from vreg needs to hit A

dahermit · Sep 12, 2014

I added to the schematic:

JMOR · Sep 12, 2014

(quoted from post at 19:37:02 09/12/14) I added to the schematic:

K, the ammeter/gen/VR /batt are in the circuit such that meter should show charging as well as discharging. Might verify that the mounting hardware for the meter is not shorting the two terminals together. Some have numerous insulating washers and such that if not installed just right, can be a problem. Just to be sure gen is charging battery, measure voltage across battery terminals before starting & again after & while running at speed for several minutes. If charging, you should see battery voltage rise by about a volt.

beastlybirdie · Sep 12, 2014

First of all, does the generator work? The reason I ask is you say you have 6 volts showing on your meter while running. Ammeters register amps, not volts. Running should be higher than 6 volts.

dahermit · Sep 12, 2014

I do not know if my generator is working. The
Ammeter has not been working for a couple of
years, but the generator has been working (or the
battery would have discharged with use), but as of
late, I have found the battery to be discharged
after non-use. So, I decided that it was time to
fix the ammeter to monitor the generator...one
step at a time so to speak. Therefore, I do not
know if the generator is producing anymore or not.
What I do know is that sometimes the battery is
fully charged and sometimes not. In any event,
when I check the battery with a multimeter and the
throttle at 3/4, there is no increase in voltage
from the normal 6 volts when it is not running.

dahermit · Sep 12, 2014

Thanks, I will check the ammeter to see if it is
shorting as you suggested.

greywolf224 · Sep 12, 2014

As Soundguy suggested did you polarized the generator by touching a wire between The Batt and ARM terminals of the voltage regulator while the engine is off. Then start the engine and measure the voltage at the battery to see if you have an increase in voltage.

JMOR · Sep 12, 2014

(quoted from post at 23:31:33 09/12/14) I do not know if my generator is working. The
Ammeter has not been working for a couple of
years, but the generator has been working (or the
battery would have discharged with use), but as of
late, I have found the battery to be discharged
after non-use. So, I decided that it was time to
fix the ammeter to monitor the generator...one
step at a time so to speak. Therefore, I do not
know if the generator is producing anymore or not.
What I do know is that sometimes the battery is
fully charged and sometimes not. In any event,
when I check the battery with a multimeter and the
throttle at 3/4, there is no increase in voltage
from the normal 6 volts when it is not running.

o battery voltage increase when running at speed, vs sitting with engine off, is a very good signal that the generator/VR is not functioning correctly.

dahermit · Sep 13, 2014

If the generator is working, could I not connect my multimeter to the Armature and ground terminals (with engine running), and see voltage?

JMOR · Sep 14, 2014

(quoted from post at 22:01:30 09/13/14) If the generator is working, could I not connect my multimeter to the Armature and ground terminals (with engine running), and see voltage?

es, see something, but how much will depend on field current. Residual mag alone will not result in much arm voltage output.

dahermit · Sep 14, 2014

I do not understand. If the engine were running and
the generator was working properly, why would there
be only residual magnetism in the field? Why would
there not be at least a full six volts from the arm?

JMOR · Sep 14, 2014

(quoted from post at 07:53:14 09/14/14) I do not understand. If the engine were running and
the generator was working properly, why would there
be only residual magnetism in the field? Why would
there not be at least a full six volts from the arm?

t is all in the details as Ross Perot used to say. In order for the field coils to see full voltage (6 or more), the arm must produce it AND the field terminal must be grounded (normally via a functional VR).

dahermit · Sep 14, 2014

I polorized the generator, fired it up this A.M.
and got zero volts across the Arm and the Ground.
So in other words, I still do not know if the no
volts is the fault of the Generator or the Voltage
Regulator?
The good news is that I have a new generator in my
possession and I guess I will have to swap it with
the suspect mounted one on the tractor (waiting
for a keyed pulley to fit it, the generator on the
8N now is held on with a clip, its pulley will not
fit the new generator). The bad news is, if it is
the Voltage Regulator, I will still have to replace that
to remedy the problems.

JMOR · Sep 14, 2014

(quoted from post at 13:43:48 09/14/14) I polorized the generator, fired it up this A.M.
and got zero volts across the Arm and the Ground.
So in other words, I still do not know if the no
volts is the fault of the Generator or the Voltage
Regulator?
The good news is that I have a new generator in my
possession and I guess I will have to swap it with
the suspect mounted one on the tractor (waiting
for a keyed pulley to fit it, the generator on the
8N now is held on with a clip, its pulley will not
fit the new generator). The bad news is, if it is
the Voltage Regulator, I will still have to replace that
to remedy the problems.

ill not hurt a thing to simply ground the field and then look for arm voltage running at speed.

greywolf224 · Sep 14, 2014

After making sure all connections are bright and tight Ground the field at the genny. And jumper the ARM and BATT at the VR in essence by-passing the VR and full fielding the genny.

If your genny is working you should see a voltage increase at the battery and assume the genny is working ok.

Don't run it this way other than a few minutes. Otherwise you will overcharge the battery and Over run the generator.

Ammeter not working.

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