40S voltage regulator

(F) wired to the generators Field Terminal (smaller of its 2 output studs),

(ARM) or (GEN) on some, wired to the generators Armature output terminal (larger of 2 output studs), and

(BAT) connected to the battery to charge it, ususally via an ammeter where its wired to its load (non battery) side. The other side of ammeter is wired to the battery to charge it, usually off the starter post or even direct to the batterys non grounded post.

On the 4 wire Voltage Regulators, they have terminals marked:

(F) wired to the generators Field Terminal,

(ARM) or (GEN) on some, wired to the generators Armature output terminal,

(BAT) which is connected to the battery to charge it via an ammeter where its wired to its load (non battery) side, and

(L) Load which is the power feed wire that supplies current and voltage to loads such as lights and the ignition coil, via the tractors light and ignition switch(es).

NOW FOR THE DIFFERENCE

On the 3 wire Voltage Regulators, loads like ignition and lights are fed from the ammeters load (non battery) side, which is the same place the Voltage Regulators (BAT) terminal is connected.

HOWEVER

On the 4 wire Voltage Regulators, loads like ignition and lights ARE NOT connected to the ammeters load side, but are fed via the (L) Load terminal on the Voltage Regulator, via the tractors light and ignition switch(es).

So, the L terminal you asked about is what feeds and powers loads like lights and ignition etc., via the switch, instead of them feedign off the ammeters load side as on 3 wire Voltage Regulators.

I hope this helps and provides guidance to those who are tryign to wire either type of Voltage Regulators.

God Bless the USA and please pray for our troops,

Ol John T Nordhoff in Indiana

On 3 wire Voltage Regulators, the light and ignition switch(es) get their power from the ammeter's load side.

On 4 wire Voltage Regulators, the light and ignition switch(es) get their power off the (L) Load terminal on the Voltage Regulator.

The power, of course, to feed lights and ignition still must come from the battery, its just that the L terminal is the feed point for the 4 wire VR's while the load (non battery) side of the ammeter is the feed point on the 3 wire VR's.

The ammeter still correctly shows the amount of current in or out the battery on 3 OR 4 wire VR's, because even on 4 wire VR's, the current out the (L)terminal is still supplied by the VR's BAT terminal, which is fed from the ammeters load side.

The only difference is where the ignition and light switch(es) gets its main feed wire. i.e., either the (L) terminal on the VR (4 wire VR) or the load side of the ammeter (3 wire VR), but all still comes from the battery and passes through the ammeter first.

The (L) terminal doesnt know when to turn on lights or ignition, its always HOT, it just supplies the current and voltage to the switches (Loads) so when you turn them on, they work. In answer to one of your questions, the L terminal gets its power from the battery (via internal VR wiring to BAT terminal) before the tractor is running. In answer to another of your questions, on the 3 wire VR system, the load side of the ammeter is the hot feed wire to the switch(es) so when you turn them on current flows out the battery, through the ammeter, then powers the lights or ignition coil etc.

Hope this helps. Post back any more questions. Take care. Ol John T

[email protected]

These are the exact reasons that I asked Clooney for a copy of the 12 volt neg ground wiring diagram for single wire alternators.

Jeff