wiring famall cub

What is the L terminal on a regulator for a farmall cub with battery ignition? Is it the load terminal?
Does the voltage for the light switch connect by
a wire from from the light switch to the ammeter?

The L terminal on the VR can be either connected to the light switch to supply it directly with current from the generator, (it works just fine doing that, or it can be ignored, and the light switch can be connected to the load side of the amp meter (that is the side not connected to the start switch). The L terminal allows a separate (additional) path for current, supplementing the Bat to Amp meter wire. It was used on many IH tractors (and probably other brands as well) to brighten the lights. Jim

Youre right, and Jim also of course, IT IS THE LOAD TERMINAL designed to feed hot battery voltage to loads (Lights and Ignition) instead them being fed from the Load (NOT battery/starter) side of the ammeter in cases where this in no 4th LOAD VR terminal (i.e. 3 terminal VR's). The 4 terminal VR's are reported to do a better job of regulation and prevent overcharging by feeding genny current direct to loads versus the cutout relay and BAT terminal then up to the Load side of the ammeter. On Deeres they began using them on the early lettered series but went to 3 terminal VR's on later models, while IHC used them beginning with H, M etc I believe. I wish I had an INTERNAL wiring and relay diagram of a 4 terminal so I could compare it to 3 terminal VR operation, anybody got a detailed INTERNAL 4 terminal VR diagram???

John T

Jim or Bob if you read this, on a 3 terminal VR, load (lights and ignition) current has to pass through the cutout relay to the VR BAT terminal then up to load side of ammter where it can get to loads. On the 4 terminal its fed directly off the L so it dont have to take that path HOWEVER I dont have any detailed 4 terminal internal schematic and Im not quite sure what takes place and how they work exactly (current path). Ive read they regulate more precise and are better at preventing overcharging, they would have to be more expensive to produce and wonder why they stopped using them on Deeres or IHC???

Any thoughts or detailed internals???

John T (never too old to learn)

Discussion, not useful info for the Cub owner!

The lights must work with the engine stopped. Thus if the L terminal was connected to the ARM input to the VR the turning on of the lights would place current into the arm windings (and field windings) as though it was being polarized. Battery drain from where ever the bat voltage was coming from. ( I reject that idea, it must be down stream toward the battery within the VR from the cutout. If there are two sets of contacts in the VR's cutout relay, one to BAT and one to L it would work, but seems to me to be just a way to assure less voltage drop to the lights by doubling the 10gauge wire to the light box. if there is only one set of contacts in the VR's cutout, it would need to be only as healthy as needed (gen current must flow through it when bat is low and lights are on.) I am also interested in a full diagram. Fun discussion, Jim

I think its much more complicated then simply an extra jumper/wire from a BAT terminal over to the L terminal but I just dont know whats inside. YES THATS CORRECT,,,,,,, L wouldnt be hot not running if it were to the gennys ARM,,,,

If all it was is L jumped direct to BAT (to get the 4th terminal), there wouldnt be any need for the L terminal, simply wire loads to BAT (versus ammeter) n be done with it,,, Change the terminal label from BAT to BAT & LOAD, theres gotta be more to it then simply that, BUT WHAT??

Fun for us sparkies (Nerds lol), boringggggggg for the rest im sure

John T

More stuff Jim
Interesting not a direct hit, but good info

John,
Here's a link to an old Delco-Remy service bulletin that may help

http://chevy.oldcarmanualproject.com/electrical/49dr324/1r11102.htm

First off, in case ejensen doesn't have his wiring question completely answered, here is the applicable diagram from the ATIS Cub FAQ.

Now, on to the question about what the "L" terminal contributes to the whole system. Rvirgil came up with the right diagram. I am inserting an equivalent diagram from GSS-1310 (stored on Rudi's Cub manual server).

The current produced by the generator goes into the regulator at the GEN terminal, through a coil in the cut-out relay, through the cut-out contacts, then through the current regulating coil of the regulator relay and finally out the BAT terminal. The L terminal is tapped into this circuit BETWEEN the cut-out contacts and the current coil on the regulator relay. Thus, when the generator is charging, the load (lights, ignition) are fed through from the generator and through the cut-out contacts then directly to the L terminal and that load will not be included in the current limit of the regulator. That way the current limit is only limiting the current actually going to the battery.

Then the generator is NOT charging, battery power feeds into the BAT terminal of the regulator, passes through the current coil of the regulator relay and on to the L terminal to power the lights and ignition. The cut-out contacts will be open preventing a feed into the generator.

Woooooooo Hooooooooo THATS EXACTLYYYYYYYY WHAT I WAS LOOKIN FOR. It explains the operation and I knew it was a bit more complex then simply an extension direct off the BAT terminal...

THANKS I have that picture and URL link saved

John T

GREAT INFO, that and what was also posted below explains how the L terminal operates as I knew it was more complex then simply being tied direct to the BAT terminal but I had no diagrams I SURE DO NOW, THANKS

John T

Coupled with the sensing concepts from the site I found makes real sense. It also explains why it was eventually abandoned. Cost and complexity for probably little real advantage. Jim