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Subject: ammeter / light

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Peter Nelson    Posted 10-23-2018 at 08:11:18 [URL] [DELETE]        [Reply] [Email]  
  • ammeter / light
  • Have a 6 volt, front mount 8n. Installed new 6 volt headlights and rear light: they work fine. The ammeter has never worked, and the tractor works fine, no trouble with battery charging etc. Replaced ammeter. Ammeter does not move a bit when tractor is started: turn on the new lights, and it shows a discharge. This does not look good for snow plowing at night. What to do?? Thanks, PN.

    K.LaRue-VA    Posted 10-23-2018 at 21:29:33 [URL] [DELETE]        [Reply] [No Email]  
  • Re: ammeter / light
  • I keep my batteries on maintainers. I've found that the charge level maintained by most maintainers and other plug-in battery chargers is slightly higher than the "fully charged" level the 6 volt regulators are set to. My 6 volt tractors rarely show much charging current. Winter is coming, which sometimes means a few more seconds or a second crank cycle if I stall the engine trying to get rolling too soon. I expect to see a little more charge current in colder months.

    Ignition current is too little to do more than maybe cause the ammeter to wiggle when the key is turned on and off.

    At anything above idle, turning lights on should result in a momentary negative dip of the ammeter needle. Likewise switching lights off should cause a momentary positive reading. The regulator should very quickly react to lights on or off and bring the needle back where it was before the load changed.

    Tim Daley(MI)    Posted 10-24-2018 at 08:15:03 [URL] [DELETE]        [Reply] [No Email]  
  • Re: ammeter / light
  • Yes, I bought a Battery Tender Jr; the 6V version, for less than $30 on-line, shipping included. WALMART carries them but mine did not have the 6V version. It was cheaper buying on-line (fleabay) than ordering one thru wally world. Best to use them when tractor sets idle for 30 days or more. The biggest thing that depletes battery life is constant discharging and recharging. I normally got 5-6 years on a good 6V (Interstate) brand battery. Now with my Battery Tender I am keeping better track on life span.

    Tim Daley(MI)

    Tony C    Posted 10-23-2018 at 18:00:21 [URL] [DELETE]        [Reply] [No Email]  
  • Re: ammeter / light
  • Assuming the needle only goes a needle width or less and doesn't peg hard to the discharge side, and the lights are working you have the lights wired correctly.

    If the charging system is keeping the battery charged it's probably functioning as it should. You can use a known to be good accurate ammeter in line between the regulator and battery to check output. You can also use a volt meter or meter that reads bleed voltage off the hot battery cable. The latter two methods only read voltage, not amps however. Or you can run it with the lights on doing chores as you do normally. If the battery stays charged you have your answer.

    Remember this. A Ford in good tune (or any other tractor of the age) starts easily especially in moderate weather with minimal strain on the battery. Additionally there is little battery draw through the primary system to keep it running.

    Fuel and ignition off, lights on if not wired through the ignition. Wing it over for a good bit. Don't worry about overheating the starter, but don't go nuts.. Those starters are tough and built to take it. THen start it and see if your meter moves.

    Discharge at idle is normal. Sometimes it will take half throttle to get the gauge to show any charge. And yes.... I know it's not a 12v system with an alternator. It still takes speed off idle for a positive charge to be indicated on the amp meter.

    The ammeters in those tractors have wide needles, wide marks and relatively low output charging systems. Even at full charge you may not get more than a full needle width movement in the positive direction when charging a low battery.

    True test will come this winter. Lights, radio, heater fans,(on high blow),butt warmer, steering wheel and cup holder heaters on high as you break trail from the house to the county road. Stay warm.


    Tim Daley(MI)    Posted 10-24-2018 at 07:54:38 [URL] [DELETE]        [Reply] [No Email]  
  • Re: ammeter / light
  • AMMETERS, especially the induction ones, have a +/- tolerance of 20%. When cranking, the gauge should show a minute amount of movement. Normal range when running and charging should be between +3 and +7 amps. Gotsta remember too many lights will exceed the amp draw. Lighting kits had two headlights and one taillight. Early 8N genny output rated at 11.5 AMPS. OHM's Law applied: sealed beam 6V lamp = 35 watts. Taillight bulb about 3 watts. Introduce a 6V worklight, 25 Watts, and recompute. One reason FORD went to a 3rd Brush generator, starting in 1940 with s/n 9N-12500, was the intent to increase the charging rate when using the headlights, and reduce it when lights not in use. It took them until mid-8N production to drop the 3rd Brush and increase generator output to 20 amps.

    Tim Daley(MI)

    Tim Daley(MI)    Posted 10-23-2018 at 09:05:04 [URL] [DELETE]        [Reply] [Email]  
  • Re: ammeter / light
  • Like Jack stated, be sure to follow the correct wiring PICTOGRAM supplied by JMOR for your 8N. The May, 1949 MPC has the lighting diagram -see LINK below. Though you say it is 6V, is the circuit wired correctly throughout? The generator should be a 3-wire/3-Brush unit, with a Voltage Regulator, and ballast resistor in the circuit. Are you using original or repops of the original lights? The OEM wiring used 1 power wire to the lamps, and the ground was made to the metal body anywhere. A slight discharge on the AMMETER when the lights are ON is normal. The generator may or not be charging the battery. First is to verify ALL the wiring is correct. You can pull the battery, generator, and VR and take to your trusty local starter/alternator shop. He can bench test everything. If generator is in need of a rebuild, and he doesn't know these old Ford systems, I can do it -email is open. Sometimes with these early 8N generators they are missing the tiny belt tension arm, p/n 8N-10145, and thus create a non-charging issue because the fan belt isn't tight and the generator isn't charging properly. If you are missing this arm I have a bunch I made exactly like the original. If the battery is not sustaining a full charge under load, it won't have enough juice to crank over the engine and certainly nor run lights.


    Tim Daley(MI)

    Jack - Iowa    Posted 10-23-2018 at 08:29:21 [URL] [DELETE]        [Reply] [Email]  
  • Re: ammeter / light
  • Sounds like a wiring error. Measure battery voltage, engine off, and then repeat with engine at moderate RPM's. This will tell you for sure if the generator is operating. After that it will be a job of tracing per a known good schematic. See JMOR's diagrams.

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