Farmall 340 electric stuph

Al L. in Wisc.

Well-known Member
The 340 has been converted to 12 volts and I am replacing gauges.

*The key switch has off-on and the third position won't allow the tractor to start but will drain the battery if left in this position, I found out. Fellow who wired it said he could have used the two position switch off-on; correct? Current contacts: one to alternator, one to starter button and one to front contact of resistor: see photo above. In the photo, the resistor rear contact has a wire going to the coil and another wire from here goes to ??? as I didn't label it.

New gauges include light, amp and oil. I would appreciate help in getting this wired correctly. Thank you
a179082.jpg
 
The front terminal on the resistor should be connected to
the "on" ignition switch terminal.
The wire heading to the rear should be connected to the
R terminal on the starter solenoid for full voltage while
cranking the engine.
Jim
 
Is the alternator a Delco 10si 3 wire? The extra position on the switch may be an accessory position. Which is generally one click to counterclockwise of the off position. He may have worked around one of the issues that comes up when you install a alternator on a tractor. If direct wired the engine will continue to run after the key is turned off due to the alternator continues to supply 12v to the ignition wire it is connected to. If you use an accessory type switch you can avoid this by wiring your excite wire (S1 on the Delco, side spade term.) to the accessory contact of the switch. The common way to avoid the run on is to install a diode (prevents two way power flow) in the excite wire or a small lamp. In the case of the lamp the small filament does not have enough resistance to power the ignition coil properly, so it just glows until the engine dies. Other brands of alternators may require similar wiring, I?m just not sure of the specific designation for them. Amp gauge should wire just like original. Basically one wire to battery power, generally picked up at the battery terminal of the starter. All other loads and the large feed wire from the alternator post on back to the opposite terminal.
 

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