Question on alternator

henryv11 · Jul 29, 2016

I have installed alternators on 3 of my tractors. I have used a toggle sw. to excite the
alternator. Could someone explain to me how the lamp,or resistor work. Wouldn't the light
On the lamp be on all the time. I know the diode only lets current go in one direction. I
like the toggle sw. because it is a manual operation but if someone else is driving the
tractor they might not know about the sw. so the other method would be better in that case.

Thank you

old · Jul 29, 2016

A light bulb or resister let just enough power to pass to let the alternator excite. As for the bulb if you use the correct one it becomes an idiot light and once the alternator has been excited the bulb goes out just like the idiot lights on cars do if things are working as they should be

Hayfarmer · Jul 29, 2016

on my 560 Diesel the previous owner put a switch int he oil pressure line so that alternator is excited as soon as there is oil pressure but shuts off when engine is stopped.

used red MN · Jul 29, 2016

And to add to old's post, the excite wire is energized with voltage from the alternator during normal run cycle. So voltage from the ignition and from the alternator is applied on each side of the bulb so it does not light in normal run phase. When the ignition is switched off its circuit becomes the ground side going through the coil and points to the distributor housing, Even though it is a pulsing ground circuit due to the open and closing points. The excite wire from the alternator continues to be the positive power for the lamp. Now if the correct bulb is chosen (such as a 194 dash bulb) the filament cannot carry enough amperage to support the draw of the coil so the bulb just glows until the engine stops. Connecting the excite wire directly to the ignition circuit would work fine in terms of the alternator being excited to charge, but the engine would not die due to the power being supplied from the excite circuit. Thus the reason to add the bulb or diode. And once the alternator stops turning and charging the excite wire is not powered so there is no draw on the battery. Hope this helps.

David G · Jul 29, 2016

Just run a wire with diode in series from the coil.

Simple as it gets.

old · Jul 29, 2016

Yep that works well if you remember to tell them the line on the diode goes towards the alternator.

henryv11 · Jul 29, 2016

Thank You that helps me understand it better. The last tractor I put one on was a Super C with a mag so I would have had to use a different power source.

Question on alternator

henryv11

Member

old

Well-known Member

Hayfarmer

Well-known Member

used red MN

Well-known Member

David G

Well-known Member

old

Well-known Member

henryv11

Member

Similar threads