erskine2017
Member
Dear Buckeye Al, Your analogy of comparing the 24 Volt system to household wiring is helpful, but it also has limitations. 1)Unlike the house, the tractor has two power sources a)the batteries b)the generator. 2)With an unbalanced load even with the middle wire hooked up, the voltage at the midpoint will vary both because the batteries will charge unequally and the different resistances of the loads will cause the voltage to split unequally according to Ohm's Law and Kirchoff's Law. The middle wire will alleviate this situation but not eliminate it. This is different than household as the midpoint voltage will not change with uneven loads. 3) Even with the middle wire hooked up there can still be burned out bulbs and a ruined or inaccurate fuel gauge. The most common problem is old, bare wiring touching the frame which can allow 24 volts instead of 12 or more with the tractor running to be applied to a light or gauge. 4) A starter, generator, or voltage regulator grounding to the frame will have the same effect. I remember having a farmer having a bunch of wrenches in a tool box and one touched the case of the voltage regulator which is "hot" causing the same result. 5) An interesting phenomenon occurs with the operation of the fuel gauge when the middle wire is missing. With the wire missing, the fuel gauge can not find ground and won't work. However when you turn the lights on the gauge will find ground through one of the lights which sounds spooky. 6) Ground is a controversial topic and even has philosophical and metaphysical overtones. It originally meant a wire going to the earth. The term can be used as the frame of a car or tractor that connects to a a battery terminal(hence positive or negative ground). Cars and tractors all have "floating grounds", as there is no earth connection. 7) Ground can also be defined as a reference point of zero electrical or voltage potential which can be used to measure all other voltages in the circuit. In the 24 volt system the best reference point is the positive terminal of the battery that attaches to the isolated terminal on the barrel of the starter. This is "ground" or return if you prefer with the negative terminal attached to the solenoid as supply. 8) The only time there are 12 volt circuits is with the tractor stopped. With the tractor running and the generator in charge(pun intended),there is a 24 volt series-parallel circuit. This is easier to visualize if you take the batteries out and put them on the floor. With the lights on and generator running, the system will work just fine with equal loads. 9) The system is complicated and has some quirks. Some of which are covered in my articles in "Green Magazine." Thank you for your input and your great comments on the Forum.
